Merge branch 'master' into rj/visibility-cleanup

* master: (34 commits)
  miniconf: update example usage
  apps: spi isrs are spi errors
  pounder/timestamp: docs updatew
  pll: update tests and benches
  pll: merge advance into update (like rpll)
  pll: add advance()
  pounder_timestamper: use input capture prescaler
  Revert "Revert "pounder timestmper: don't use DMA""
  miniconf: add some checks, simplify
  miniconf.py: make retain an option
  refactor flatten_closures
  clippy recursion
  fix a few clippy lints on files that are touched
  Revert "pounder timestmper: don't use DMA"
  pounder timestmper: don't use DMA
  lockin: dma fence
  lockin: port to fast double buffered DMA
  dma: implement overflow checking
  pounder: clippy
  pounder: add comment on channel enum
  ...

Cargo.lock

@@ -404,8 +404,9 @@ dependencies = [
 
 [[package]]
 name = "mcp23017"
-version = "0.1.1"
+version = "1.0.0"
-source = "git+https://github.com/lucazulian/mcp23017.git?rev=523d71d#523d71dcb11fc0ea4bd9385ef2527ae7a7eee987"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2c32fd6627e73f1cfa95c00ddcdcb5a6a6ddbd10b308d08588a502c018b6e12c"
 dependencies = [
  "embedded-hal",
 ]
@@ -775,8 +776,7 @@ dependencies = [
 [[package]]
 name = "stm32h7xx-hal"
 version = "0.9.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
+source = "git+https://github.com/quartiq/stm32h7xx-hal.git?rev=b0b8a93#b0b8a930b2c3bc5fcebc2e905b4c5e13360111a5"
-checksum = "67034b80041bc33a48df1c1c435b6ae3bb18c35e42aa7e702ce8363b96793398"
 dependencies = [
  "bare-metal 1.0.0",
  "cast",

Cargo.toml

@@ -45,20 +45,19 @@ ad9959 = { path = "ad9959" }
 miniconf = "0.1.0"
 shared-bus = {version = "0.2.2", features = ["cortex-m"] }
 serde-json-core = "0.4"
+mcp23017 = "1.0"
 
 # rtt-target bump
 [dependencies.rtt-logger]
 git = "https://github.com/quartiq/rtt-logger.git"
 rev = "70b0eb5"
 
-# rewrite
+# fast double buffered DMA without poisoning and buffer swapping
-[dependencies.mcp23017]
-git = "https://github.com/lucazulian/mcp23017.git"
-rev = "523d71d"
-
 [dependencies.stm32h7xx-hal]
 features = ["stm32h743v", "rt", "unproven", "ethernet", "quadspi"]
-version = "0.9.0"
+# version = "0.9.0"
+git = "https://github.com/quartiq/stm32h7xx-hal.git"
+rev = "b0b8a93"
 
 # link.x section start/end
 [patch.crates-io.cortex-m-rt]

ad9959/src/lib.rs

@@ -43,6 +43,7 @@ pub enum Mode {
 
 /// The configuration registers within the AD9959 DDS device. The values of each register are
 /// equivalent to the address.
+#[allow(clippy::upper_case_acronyms)]
 pub enum Register {
     CSR = 0x00,
     FR1 = 0x01,
@@ -596,6 +597,22 @@ impl ProfileSerializer {
         self.index += value.len() + 1;
     }
 
+    fn pad(&mut self) {
+        // Pad the buffer to 32-bit (4 byte) alignment by adding dummy writes to CSR and LSRR.
+        match self.index & 3 {
+            3 => {
+                // For a level of 3, we have to pad with 5 bytes to align things.
+                self.add_write(Register::CSR, &[(self.mode as u8) << 1]);
+                self.add_write(Register::LSRR, &[0, 0]);
+            }
+            2 => self.add_write(Register::CSR, &[(self.mode as u8) << 1]),
+            1 => self.add_write(Register::LSRR, &[0, 0]),
+            0 => {}
+
+            _ => unreachable!(),
+        }
+    }
+
     /// Get the serialized profile as a slice of 32-bit words.
     ///
     /// # Note
@@ -604,21 +621,8 @@ impl ProfileSerializer {
     ///
     /// # Returns
     /// A slice of `u32` words representing the serialized profile.
-    pub fn finalize<'a>(&'a mut self) -> &[u32] {
+    pub fn finalize<'a>(&'a mut self) -> &'a [u32] {
-        // Pad the buffer to 32-bit alignment by adding dummy writes to CSR and LSRR.
+        self.pad();
-        let padding = 4 - (self.index % 4);
-        match padding {
-            1 => {
-                // For a pad size of 1, we have to pad with 5 bytes to align things.
-                self.add_write(Register::CSR, &[(self.mode as u8) << 1]);
-                self.add_write(Register::LSRR, &[0, 0]);
-            }
-            2 => self.add_write(Register::CSR, &[(self.mode as u8) << 1]),
-            3 => self.add_write(Register::LSRR, &[0, 0]),
-            4 => {}
-
-            _ => unreachable!(),
-        }
         unsafe {
             core::slice::from_raw_parts::<'a, u32>(
                 &self.data as *const _ as *const u32,

dsp/benches/micro.rs

@@ -44,11 +44,11 @@ fn pll_bench() {
     let mut dut = PLL::default();
     println!(
         "PLL::update(t, 12, 12): {}",
-        bench_env(0x241, |x| dut.update(*x, 12, 12))
+        bench_env(Some(0x241), |x| dut.update(*x, 12, 12))
     );
     println!(
         "PLL::update(t, sf, sp): {}",
-        bench_env((0x241, 21, 20), |(x, p, q)| dut.update(*x, *p, *q))
+        bench_env((Some(0x241), 21, 20), |(x, p, q)| dut.update(*x, *p, *q))
     );
 }
 

dsp/src/atan2.rs

@@ -77,6 +77,8 @@ pub fn atan2(y: i32, x: i32) -> i32 {
 
     if sign.1 {
         angle = angle.wrapping_neg();
+        // Negation ends up in slightly faster assembly
+        // angle = !angle;
     }
 
     angle

dsp/src/pll.rs

@@ -45,7 +45,7 @@ impl PLL {
     /// The signal's phase/frequency is reconstructed relative to the sampling period.
     ///
     /// Args:
-    /// * `x`: New input phase sample.
+    /// * `x`: New input phase sample or None if a sample has been missed.
     /// * `shift_frequency`: Frequency error scaling. The frequency gain per update is
     ///   `1/(1 << shift_frequency)`.
     /// * `shift_phase`: Phase error scaling. The phase gain is `1/(1 << shift_phase)`
@@ -55,26 +55,31 @@ impl PLL {
     /// A tuple of instantaneous phase and frequency (the current phase increment).
     pub fn update(
         &mut self,
-        x: i32,
+        x: Option<i32>,
         shift_frequency: u8,
         shift_phase: u8,
     ) -> (i32, i32) {
         debug_assert!((1..=30).contains(&shift_frequency));
         debug_assert!((1..=30).contains(&shift_phase));
-        let e = x.wrapping_sub(self.f);
+        let f = if let Some(x) = x {
-        self.f = self.f.wrapping_add(
+            let e = x.wrapping_sub(self.f);
-            (1i32 << (shift_frequency - 1))
+            self.f = self.f.wrapping_add(
-                .wrapping_add(e)
+                (1i32 << (shift_frequency - 1))
-                .wrapping_sub(self.x)
+                    .wrapping_add(e)
-                >> shift_frequency,
+                    .wrapping_sub(self.x)
-        );
+                    >> shift_frequency,
-        self.x = x;
+            );
-        let f = self.f.wrapping_add(
+            self.x = x;
-            (1i32 << (shift_phase - 1))
+            self.f.wrapping_add(
-                .wrapping_add(e)
+                (1i32 << (shift_phase - 1))
-                .wrapping_sub(self.y)
+                    .wrapping_add(e)
-                >> shift_phase,
+                    .wrapping_sub(self.y)
-        );
+                    >> shift_phase,
+            )
+        } else {
+            self.x = self.x.wrapping_add(self.f);
+            self.f
+        };
         self.y = self.y.wrapping_add(f);
         (self.y, f)
     }
@@ -86,7 +91,7 @@ mod tests {
     #[test]
     fn mini() {
         let mut p = PLL::default();
-        let (y, f) = p.update(0x10000, 8, 4);
+        let (y, f) = p.update(Some(0x10000), 8, 4);
         assert_eq!(y, 0x1100);
         assert_eq!(f, y);
     }
@@ -100,7 +105,7 @@ mod tests {
         let mut x = 0i32;
         for i in 0..n {
             x = x.wrapping_add(f0);
-            let (y, f) = p.update(x, shift.0, shift.1);
+            let (y, f) = p.update(Some(x), shift.0, shift.1);
             if i > n / 4 {
                 assert_eq!(f.wrapping_sub(f0).abs() <= 1, true);
             }

dsp/src/tools.rs

@@ -87,20 +87,3 @@ pub fn macc_i32(y0: i32, x: &[i32], a: &[i32], shift: u32) -> i32 {
         .fold(y0, |y, xa| y + xa);
     (y >> shift) as i32
 }
-
-/// Combine high and low i32 into a single downscaled i32, saturating the type.
-pub fn saturating_scale(lo: i32, hi: i32, shift: u32) -> i32 {
-    debug_assert!(shift & 31 == shift);
-
-    let shift_hi = 31 - shift;
-    debug_assert!(shift_hi & 31 == shift_hi);
-
-    let over = hi >> shift;
-    if over < -1 {
-        i32::MIN
-    } else if over > 0 {
-        i32::MAX
-    } else {
-        (lo >> shift) + (hi << shift_hi)
-    }
-}

dsp/src/unwrap.rs

@@ -16,6 +16,27 @@ pub fn overflowing_sub(y: i32, x: i32) -> (i32, i8) {
     (delta, wrap)
 }
 
+/// Combine high and low i32 into a single downscaled i32, saturating monotonically.
+///
+/// Args:
+/// `lo`: LSB i32 to scale down by `shift` and range-extend with `hi`
+/// `hi`: MSB i32 to scale up and extend `lo` with. Output will be clipped if
+///     `hi` exceeds the output i32 range.
+/// `shift`: Downscale `lo` by that many bits. Values from 1 to 32 inclusive
+///     are valid.
+pub fn saturating_scale(lo: i32, hi: i32, shift: u32) -> i32 {
+    debug_assert!(shift > 0);
+    debug_assert!(shift <= 32);
+    let hi_range = -1 << (shift - 1);
+    if hi <= hi_range {
+        i32::MIN - hi_range
+    } else if -hi <= hi_range {
+        hi_range - i32::MIN
+    } else {
+        (lo >> shift) + (hi << (32 - shift))
+    }
+}
+
 /// Overflow unwrapper.
 ///
 /// This is unwrapping as in the phase and overflow unwrapping context, not

miniconf.py

@@ -16,6 +16,7 @@ from gmqtt import Client as MqttClient
 
 LOGGER = logging.getLogger(__name__)
 
+
 class Miniconf:
     """An asynchronous API for controlling Miniconf devices using MQTT."""
 
@@ -33,64 +34,64 @@ class Miniconf:
             client: A connected MQTT5 client.
             prefix: The MQTT toptic prefix of the device to control.
         """
-        self.uuid = uuid.uuid1()
         self.request_id = 0
         self.client = client
         self.prefix = prefix
         self.inflight = {}
         self.client.on_message = self._handle_response
-        self.client.subscribe(f'{prefix}/response/{self.uuid.hex}')
+        self.response_topic = f'{prefix}/response/{uuid.uuid1().hex}'
+        self.client.subscribe(self.response_topic)
 
-    def _handle_response(self, _client, _topic, payload, _qos, properties):
+    def _handle_response(self, _client, topic, payload, _qos, properties):
         """Callback function for when messages are received over MQTT.
 
         Args:
             _client: The MQTT client.
-            _topic: The topic that the message was received on.
+            topic: The topic that the message was received on.
             payload: The payload of the message.
             _qos: The quality-of-service level of the received packet
             properties: A dictionary of properties associated with the message.
         """
-        # Extract corrleation data from the properties
+        if topic == self.response_topic:
-        correlation_data = json.loads(properties['correlation_data'][0].decode('ascii'))
+            # Extract request_id corrleation data from the properties
+            request_id = int.from_bytes(
+                properties['correlation_data'][0], 'big')
 
-        # Get the request ID from the correlation data
+            self.inflight[request_id].set_result(json.loads(payload))
-        request_id = correlation_data['request_id']
+            del self.inflight[request_id]
+        else:
+            LOGGER.warn('Unexpected message on "%s"', topic)
 
-        self.inflight[request_id].set_result(json.loads(payload))
+    async def command(self, path, value, retain=True):
-        del self.inflight[request_id]
-
-
-    async def command(self, path, value):
         """Write the provided data to the specified path.
 
         Args:
             path: The path to write the message to.
             value: The value to write to the path.
+            retain: Retain the MQTT message changing the setting
+                by the broker.
 
         Returns:
             The response to the command as a dictionary.
         """
-        setting_topic = f'{self.prefix}/settings/{path}'
+        topic = f'{self.prefix}/settings/{path}'
-        response_topic = f'{self.prefix}/response/{self.uuid.hex}'
 
-        # Assign a unique identifier to this update request.
-        request_id = self.request_id
-        self.request_id += 1
-        assert request_id not in self.inflight, 'Invalid ID encountered'
-
-        correlation_data = json.dumps({
-            'request_id': request_id,
-        }).encode('ascii')
-
-        value = json.dumps(value)
-        LOGGER.info('Sending %s to "%s"', value, setting_topic)
         fut = asyncio.get_running_loop().create_future()
 
-        self.inflight[request_id] = fut
+        # Assign unique correlation data for response dispatch
-        self.client.publish(setting_topic, payload=value, qos=0, retain=True,
+        assert self.request_id not in self.inflight
-                            response_topic=response_topic,
+        self.inflight[self.request_id] = fut
-                            correlation_data=correlation_data)
+        correlation_data = self.request_id.to_bytes(4, 'big')
+        self.request_id += 1
+
+        payload = json.dumps(value)
+        LOGGER.info('Sending "%s" to "%s"', value, topic)
+
+        self.client.publish(
+            topic, payload=payload, qos=0, retain=retain,
+            response_topic=self.response_topic,
+            correlation_data=correlation_data)
+
         return await fut
 
 
@@ -100,16 +101,20 @@ def main():
         description='Miniconf command line interface.',
         formatter_class=argparse.RawDescriptionHelpFormatter,
         epilog='''Examples:
-%(prog)s dt/sinara/stabilizer afe/0='"G2"' iir_ch/0/0=\
+%(prog)s dt/sinara/dual-iir/00-11-22-33-aa-bb iir_ch/0/0=\
-'{"y_min": -32767, "y_max": 32767, "y_offset": 0, "ba": [1.0, 0, 0, 0, 0]}'
+'{"y_min":-32767,"y_max":32767,"y_offset":0,"ba":[1.0,0,0,0,0]}'
+%(prog)s dt/sinara/lockin/00-11-22-33-aa-bb afe/0='"G2"'\
 ''')
     parser.add_argument('-v', '--verbose', action='count', default=0,
                         help='Increase logging verbosity')
     parser.add_argument('--broker', '-b', default='mqtt', type=str,
                         help='The MQTT broker address')
+    parser.add_argument('--no-retain', '-n', default=False,
+                        action='store_true',
+                        help='Do not retain the affected settings')
     parser.add_argument('prefix', type=str,
                         help='The MQTT topic prefix of the target')
-    parser.add_argument('settings', metavar="KEY=VALUE", nargs='+',
+    parser.add_argument('settings', metavar="PATH=VALUE", nargs='+',
                         help='JSON encoded values for settings path keys.')
 
     args = parser.parse_args()
@@ -122,9 +127,10 @@ def main():
 
     async def configure_settings():
         interface = await Miniconf.create(args.prefix, args.broker)
-        for key_value in args.settings:
+        for setting in args.settings:
-            path, value = key_value.split("=", 1)
+            path, value = setting.split("=", 1)
-            response = await interface.command(path, json.loads(value))
+            response = await interface.command(path, json.loads(value),
+                                               not args.no_retain)
             print(f'{path}: {response}')
             if response['code'] != 0:
                 return response['code']

src/bin/dual-iir.rs

@@ -2,16 +2,19 @@
 #![no_std]
 #![no_main]
 
+use core::sync::atomic::{fence, Ordering};
+use miniconf::Miniconf;
 use serde::Deserialize;
 
 use dsp::iir;
 use stabilizer::{
+    flatten_closures,
     hardware::{
         hal, setup, Adc0Input, Adc1Input, AdcCode, AfeGain, Dac0Output,
         Dac1Output, DacCode, DigitalInput0, DigitalInput1, InputPin,
         SystemTimer, AFE0, AFE1,
     },
-    net::{Miniconf, NetworkState, NetworkUsers, Telemetry, TelemetryBuffer},
+    net::{NetworkState, NetworkUsers, Telemetry, TelemetryBuffer},
 };
 
 const SCALE: f32 = i16::MAX as _;
@@ -121,51 +124,63 @@ const APP: () = {
     #[task(binds=DMA1_STR4, resources=[adcs, digital_inputs, dacs, iir_state, settings, telemetry], priority=2)]
     #[inline(never)]
     #[link_section = ".itcm.process"]
-    fn process(c: process::Context) {
+    fn process(mut c: process::Context) {
-        let adc_samples = [
+        let process::Resources {
-            c.resources.adcs.0.acquire_buffer(),
+            adcs: (ref mut adc0, ref mut adc1),
-            c.resources.adcs.1.acquire_buffer(),
+            dacs: (ref mut dac0, ref mut dac1),
-        ];
+            ref digital_inputs,
-
+            ref settings,
-        let dac_samples = [
+            ref mut iir_state,
-            c.resources.dacs.0.acquire_buffer(),
+            ref mut telemetry,
-            c.resources.dacs.1.acquire_buffer(),
+        } = c.resources;
-        ];
 
         let digital_inputs = [
-            c.resources.digital_inputs.0.is_high().unwrap(),
+            digital_inputs.0.is_high().unwrap(),
-            c.resources.digital_inputs.1.is_high().unwrap(),
+            digital_inputs.1.is_high().unwrap(),
         ];
+        telemetry.digital_inputs = digital_inputs;
 
-        let hold = c.resources.settings.force_hold
+        let hold =
-            || (digital_inputs[1] && c.resources.settings.allow_hold);
+            settings.force_hold || (digital_inputs[1] && settings.allow_hold);
 
-        for channel in 0..adc_samples.len() {
+        flatten_closures!(with_buffer, adc0, adc1, dac0, dac1, {
-            for sample in 0..adc_samples[0].len() {
+            let adc_samples = [adc0, adc1];
-                let mut y = f32::from(adc_samples[channel][sample] as i16);
+            let dac_samples = [dac0, dac1];
-                for i in 0..c.resources.iir_state[channel].len() {
+
-                    y = c.resources.settings.iir_ch[channel][i].update(
+            // Preserve instruction and data ordering w.r.t. DMA flag access.
-                        &mut c.resources.iir_state[channel][i],
+            fence(Ordering::SeqCst);
-                        y,
+
-                        hold,
+            for channel in 0..adc_samples.len() {
-                    );
+                adc_samples[channel]
-                }
+                    .iter()
-                // Note(unsafe): The filter limits ensure that the value is in range.
+                    .zip(dac_samples[channel].iter_mut())
-                // The truncation introduces 1/2 LSB distortion.
+                    .map(|(ai, di)| {
-                let y = unsafe { y.to_int_unchecked::<i16>() };
+                        let x = f32::from(*ai as i16);
-                // Convert to DAC code
+                        let y = settings.iir_ch[channel]
-                dac_samples[channel][sample] = DacCode::from(y).0;
+                            .iter()
+                            .zip(iir_state[channel].iter_mut())
+                            .fold(x, |yi, (ch, state)| {
+                                ch.update(state, yi, hold)
+                            });
+                        // Note(unsafe): The filter limits must ensure that the value is in range.
+                        // The truncation introduces 1/2 LSB distortion.
+                        let y: i16 = unsafe { y.to_int_unchecked() };
+                        // Convert to DAC code
+                        *di = DacCode::from(y).0;
+                    })
+                    .last();
             }
-        }
 
-        // Update telemetry measurements.
+            // Update telemetry measurements.
-        c.resources.telemetry.adcs =
+            telemetry.adcs =
-            [AdcCode(adc_samples[0][0]), AdcCode(adc_samples[1][0])];
+                [AdcCode(adc_samples[0][0]), AdcCode(adc_samples[1][0])];
 
-        c.resources.telemetry.dacs =
+            telemetry.dacs =
-            [DacCode(dac_samples[0][0]), DacCode(dac_samples[1][0])];
+                [DacCode(dac_samples[0][0]), DacCode(dac_samples[1][0])];
 
-        c.resources.telemetry.digital_inputs = digital_inputs;
+            // Preserve instruction and data ordering w.r.t. DMA flag access.
+            fence(Ordering::SeqCst);
+        });
     }
 
     #[idle(resources=[network], spawn=[settings_update])]
@@ -223,22 +238,22 @@ const APP: () = {
 
     #[task(binds = SPI2, priority = 3)]
     fn spi2(_: spi2::Context) {
-        panic!("ADC0 input overrun");
+        panic!("ADC0 SPI error");
     }
 
     #[task(binds = SPI3, priority = 3)]
     fn spi3(_: spi3::Context) {
-        panic!("ADC1 input overrun");
+        panic!("ADC1 SPI error");
     }
 
     #[task(binds = SPI4, priority = 3)]
     fn spi4(_: spi4::Context) {
-        panic!("DAC0 output error");
+        panic!("DAC0 SPI error");
     }
 
     #[task(binds = SPI5, priority = 3)]
     fn spi5(_: spi5::Context) {
-        panic!("DAC1 output error");
+        panic!("DAC1 SPI error");
     }
 
     extern "C" {

src/bin/lockin.rs

@@ -2,16 +2,19 @@
 #![no_std]
 #![no_main]
 
+use core::sync::atomic::{fence, Ordering};
+use miniconf::Miniconf;
 use serde::Deserialize;
 
 use dsp::{Accu, Complex, ComplexExt, Lockin, RPLL};
 use stabilizer::{
+    flatten_closures,
     hardware::{
         design_parameters, hal, setup, Adc0Input, Adc1Input, AdcCode, AfeGain,
         Dac0Output, Dac1Output, DacCode, DigitalInput0, DigitalInput1,
         InputPin, InputStamper, SystemTimer, AFE0, AFE1,
     },
-    net::{Miniconf, NetworkState, NetworkUsers, Telemetry, TelemetryBuffer},
+    net::{NetworkState, NetworkUsers, Telemetry, TelemetryBuffer},
 };
 
 // A constant sinusoid to send on the DAC output.
@@ -154,26 +157,22 @@ const APP: () = {
     #[task(binds=DMA1_STR4, resources=[adcs, dacs, lockin, timestamper, pll, settings, telemetry], priority=2)]
     #[inline(never)]
     #[link_section = ".itcm.process"]
-    fn process(c: process::Context) {
+    fn process(mut c: process::Context) {
-        let adc_samples = [
+        let process::Resources {
-            c.resources.adcs.0.acquire_buffer(),
+            adcs: (ref mut adc0, ref mut adc1),
-            c.resources.adcs.1.acquire_buffer(),
+            dacs: (ref mut dac0, ref mut dac1),
-        ];
+            ref settings,
-
+            ref mut telemetry,
-        let mut dac_samples = [
+            ref mut lockin,
-            c.resources.dacs.0.acquire_buffer(),
+            ref mut pll,
-            c.resources.dacs.1.acquire_buffer(),
+            ref mut timestamper,
-        ];
+        } = c.resources;
-
-        let lockin = c.resources.lockin;
-        let settings = c.resources.settings;
 
         let (reference_phase, reference_frequency) = match settings.lockin_mode
         {
             LockinMode::External => {
-                let timestamp =
+                let timestamp = timestamper.latest_timestamp().unwrap_or(None); // Ignore data from timer capture overflows.
-                    c.resources.timestamper.latest_timestamp().unwrap_or(None); // Ignore data from timer capture overflows.
+                let (pll_phase, pll_frequency) = pll.update(
-                let (pll_phase, pll_frequency) = c.resources.pll.update(
                     timestamp.map(|t| t as i32),
                     settings.pll_tc[0],
                     settings.pll_tc[1],
@@ -200,45 +199,55 @@ const APP: () = {
             reference_phase.wrapping_mul(settings.lockin_harmonic),
         );
 
-        let output: Complex<i32> = adc_samples[0]
+        flatten_closures!(with_buffer, adc0, adc1, dac0, dac1, {
-            .iter()
+            let adc_samples = [adc0, adc1];
-            // Zip in the LO phase.
+            let mut dac_samples = [dac0, dac1];
-            .zip(Accu::new(sample_phase, sample_frequency))
-            // Convert to signed, MSB align the ADC sample, update the Lockin (demodulate, filter)
-            .map(|(&sample, phase)| {
-                let s = (sample as i16 as i32) << 16;
-                lockin.update(s, phase, settings.lockin_tc)
-            })
-            // Decimate
-            .last()
-            .unwrap()
-            * 2; // Full scale assuming the 2f component is gone.
 
-        // Convert to DAC data.
+            // Preserve instruction and data ordering w.r.t. DMA flag access.
-        for (channel, samples) in dac_samples.iter_mut().enumerate() {
+            fence(Ordering::SeqCst);
-            for (i, sample) in samples.iter_mut().enumerate() {
-                let value = match settings.output_conf[channel] {
-                    Conf::Magnitude => output.abs_sqr() as i32 >> 16,
-                    Conf::Phase => output.arg() >> 16,
-                    Conf::LogPower => (output.log2() << 24) as i32 >> 16,
-                    Conf::ReferenceFrequency => {
-                        reference_frequency as i32 >> 16
-                    }
-                    Conf::InPhase => output.re >> 16,
-                    Conf::Quadrature => output.im >> 16,
-                    Conf::Modulation => DAC_SEQUENCE[i] as i32,
-                };
 
-                *sample = DacCode::from(value as i16).0;
+            let output: Complex<i32> = adc_samples[0]
+                .iter()
+                // Zip in the LO phase.
+                .zip(Accu::new(sample_phase, sample_frequency))
+                // Convert to signed, MSB align the ADC sample, update the Lockin (demodulate, filter)
+                .map(|(&sample, phase)| {
+                    let s = (sample as i16 as i32) << 16;
+                    lockin.update(s, phase, settings.lockin_tc)
+                })
+                // Decimate
+                .last()
+                .unwrap()
+                * 2; // Full scale assuming the 2f component is gone.
+
+            // Convert to DAC data.
+            for (channel, samples) in dac_samples.iter_mut().enumerate() {
+                for (i, sample) in samples.iter_mut().enumerate() {
+                    let value = match settings.output_conf[channel] {
+                        Conf::Magnitude => output.abs_sqr() as i32 >> 16,
+                        Conf::Phase => output.arg() >> 16,
+                        Conf::LogPower => (output.log2() << 24) as i32 >> 16,
+                        Conf::ReferenceFrequency => {
+                            reference_frequency as i32 >> 16
+                        }
+                        Conf::InPhase => output.re >> 16,
+                        Conf::Quadrature => output.im >> 16,
+                        Conf::Modulation => DAC_SEQUENCE[i] as i32,
+                    };
+
+                    *sample = DacCode::from(value as i16).0;
+                }
             }
-        }
+            // Update telemetry measurements.
+            telemetry.adcs =
+                [AdcCode(adc_samples[0][0]), AdcCode(adc_samples[1][0])];
 
-        // Update telemetry measurements.
+            telemetry.dacs =
-        c.resources.telemetry.adcs =
+                [DacCode(dac_samples[0][0]), DacCode(dac_samples[1][0])];
-            [AdcCode(adc_samples[0][0]), AdcCode(adc_samples[1][0])];
 
-        c.resources.telemetry.dacs =
+            // Preserve instruction and data ordering w.r.t. DMA flag access.
-            [DacCode(dac_samples[0][0]), DacCode(dac_samples[1][0])];
+            fence(Ordering::SeqCst);
+        });
     }
 
     #[idle(resources=[network], spawn=[settings_update])]
@@ -300,22 +309,22 @@ const APP: () = {
 
     #[task(binds = SPI2, priority = 3)]
     fn spi2(_: spi2::Context) {
-        panic!("ADC0 input overrun");
+        panic!("ADC0 SPI error");
     }
 
     #[task(binds = SPI3, priority = 3)]
     fn spi3(_: spi3::Context) {
-        panic!("ADC1 input overrun");
+        panic!("ADC1 SPI error");
     }
 
     #[task(binds = SPI4, priority = 3)]
     fn spi4(_: spi4::Context) {
-        panic!("DAC0 output error");
+        panic!("DAC0 SPI error");
     }
 
     #[task(binds = SPI5, priority = 3)]
     fn spi5(_: spi5::Context) {
-        panic!("DAC1 output error");
+        panic!("DAC1 SPI error");
     }
 
     extern "C" {

src/hardware/adc.rs

@@ -29,15 +29,9 @@
 ///! available. When enough samples have been collected, a transfer-complete interrupt is generated
 ///! and the ADC samples are available for processing.
 ///!
-///! The SPI peripheral internally has an 8- or 16-byte TX and RX FIFO, which corresponds to a 4- or
+///! After a complete transfer of a batch of samples, the inactive buffer is available to the
-///! 8-sample buffer for incoming ADC samples. During the handling of the DMA transfer completion,
+///! user for processing. The processing must complete before the DMA transfer of the next batch
-///! there is a small window where buffers are swapped over where it's possible that a sample could
+///! completes.
-///! be lost. In order to avoid this, the SPI RX FIFO is effectively used as a "sample overflow"
-///! region and can buffer a number of samples until the next DMA transfer is configured. If a DMA
-///! transfer is still not set in time, the SPI peripheral will generate an input-overrun interrupt.
-///! This interrupt then serves as a means of detecting if samples have been lost, which will occur
-///! whenever data processing takes longer than the collection period.
-///!
 ///!
 ///! ## Starting Data Collection
 ///!
@@ -68,26 +62,26 @@
 ///! sample DMA requests, which can be completed by setting e.g. ADC0's comparison to a counter
 ///! value of 0 and ADC1's comparison to a counter value of 1.
 ///!
-///! In this implementation, single buffer mode DMA transfers are used because the SPI RX FIFO can
+///! In this implementation, double buffer mode DMA transfers are used because the SPI RX FIFOs
-///! be used as a means to both detect and buffer ADC samples during the buffer swap-over. Because
+///! have finite depth, FIFO access is slower than AXISRAM access, and because the single
-///! of this, double-buffered mode does not offer any advantages over single-buffered mode (unless
+///! buffer mode DMA disable/enable and buffer update sequence is slow.
-///! double-buffered mode offers less overhead due to the DMA disable/enable procedure).
 use stm32h7xx_hal as hal;
 
-use super::design_parameters::SAMPLE_BUFFER_SIZE;
+use super::design_parameters::{SampleBuffer, SAMPLE_BUFFER_SIZE};
 use super::timers;
 
 use hal::dma::{
     config::Priority,
     dma::{DMAReq, DmaConfig},
     traits::TargetAddress,
-    MemoryToPeripheral, PeripheralToMemory, Transfer,
+    DMAError, MemoryToPeripheral, PeripheralToMemory, Transfer,
 };
 
 /// A type representing an ADC sample.
 #[derive(Copy, Clone)]
 pub struct AdcCode(pub u16);
 
+#[allow(clippy::from_over_into)]
 impl Into<f32> for AdcCode {
     /// Convert raw ADC codes to/from voltage levels.
     ///
@@ -119,8 +113,7 @@ static mut SPI_EOT_CLEAR: [u32; 1] = [0x00];
 // processed). Note that the contents of AXI SRAM is uninitialized, so the buffer contents on
 // startup are undefined. The dimensions are `ADC_BUF[adc_index][ping_pong_index][sample_index]`.
 #[link_section = ".axisram.buffers"]
-static mut ADC_BUF: [[[u16; SAMPLE_BUFFER_SIZE]; 2]; 2] =
+static mut ADC_BUF: [[SampleBuffer; 2]; 2] = [[[0; SAMPLE_BUFFER_SIZE]; 2]; 2];
-    [[[0; SAMPLE_BUFFER_SIZE]; 2]; 2];
 
 macro_rules! adc_input {
     ($name:ident, $index:literal, $trigger_stream:ident, $data_stream:ident, $clear_stream:ident,
@@ -192,12 +185,11 @@ macro_rules! adc_input {
 
             /// Represents data associated with ADC.
             pub struct $name {
-                next_buffer: Option<&'static mut [u16; SAMPLE_BUFFER_SIZE]>,
                 transfer: Transfer<
                     hal::dma::dma::$data_stream<hal::stm32::DMA1>,
                     hal::spi::Spi<hal::stm32::$spi, hal::spi::Disabled, u16>,
                     PeripheralToMemory,
-                    &'static mut [u16; SAMPLE_BUFFER_SIZE],
+                    &'static mut SampleBuffer,
                     hal::dma::DBTransfer,
                 >,
                 trigger_transfer: Transfer<
@@ -316,6 +308,7 @@ macro_rules! adc_input {
                     // data stream is used to trigger a transfer completion interrupt.
                     let data_config = DmaConfig::default()
                         .memory_increment(true)
+                        .double_buffer(true)
                         .transfer_complete_interrupt($index == 1)
                         .priority(Priority::VeryHigh);
 
@@ -333,17 +326,14 @@ macro_rules! adc_input {
                         Transfer::init(
                             data_stream,
                             spi,
-                            // Note(unsafe): The ADC_BUF[$index][0] is "owned" by this peripheral.
+                            // Note(unsafe): The ADC_BUF[$index] is "owned" by this peripheral.
                             // It shall not be used anywhere else in the module.
                             unsafe { &mut ADC_BUF[$index][0] },
-                            None,
+                            unsafe { Some(&mut ADC_BUF[$index][1]) },
                             data_config,
                         );
 
                     Self {
-                        // Note(unsafe): The ADC_BUF[$index][1] is "owned" by this peripheral. It
-                        // shall not be used anywhere else in the module.
-                        next_buffer: unsafe { Some(&mut ADC_BUF[$index][1]) },
                         transfer: data_transfer,
                         trigger_transfer,
                         clear_transfer,
@@ -364,27 +354,17 @@ macro_rules! adc_input {
 
                 }
 
-                /// Obtain a buffer filled with ADC samples.
+                /// Wait for the transfer of the currently active buffer to complete,
+                /// then call a function on the now inactive buffer and acknowledge the
+                /// transfer complete flag.
                 ///
-                /// # Returns
+                /// NOTE(unsafe): Memory safety and access ordering is not guaranteed
-                /// A reference to the underlying buffer that has been filled with ADC samples.
+                /// (see the HAL DMA docs).
-                pub fn acquire_buffer(&mut self) -> &[u16; SAMPLE_BUFFER_SIZE] {
+                pub fn with_buffer<F, R>(&mut self, f: F) -> Result<R, DMAError>
-                    // Wait for the transfer to fully complete before continuing.  Note: If a device
+                    where
-                    // hangs up, check that this conditional is passing correctly, as there is no
+                F: FnOnce(&mut SampleBuffer) -> R,
-                    // time-out checks here in the interest of execution speed.
+                {
-                    while !self.transfer.get_transfer_complete_flag() {}
+                    unsafe { self.transfer.next_dbm_transfer_with(|buf, _current| f(buf)) }
-
-                    let next_buffer = self.next_buffer.take().unwrap();
-
-                    // Start the next transfer.
-                    self.transfer.clear_interrupts();
-                    let (prev_buffer, _, _) =
-                        self.transfer.next_transfer(next_buffer).unwrap();
-
-                     // .unwrap_none() https://github.com/rust-lang/rust/issues/62633
-                    self.next_buffer.replace(prev_buffer);
-
-                    self.next_buffer.as_ref().unwrap()
                 }
             }
         }

src/hardware/configuration.rs

@@ -233,11 +233,6 @@ pub fn setup(
     let dma_streams =
         hal::dma::dma::StreamsTuple::new(device.DMA1, ccdr.peripheral.DMA1);
 
-    // Early, before the DMA1 peripherals (#272)
-    #[cfg(feature = "pounder_v1_1")]
-    let dma2_streams =
-        hal::dma::dma::StreamsTuple::new(device.DMA2, ccdr.peripheral.DMA2);
-
     // Configure timer 2 to trigger conversions for the ADC
     let mut sampling_timer = {
         // The timer frequency is manually adjusted below, so the 1KHz setting here is a
@@ -802,7 +797,7 @@ pub fn setup(
             let scl = gpiob.pb8.into_alternate_af4().set_open_drain();
             let i2c1 = device.I2C1.i2c(
                 (scl, sda),
-                100.khz(),
+                400.khz(),
                 ccdr.peripheral.I2C1,
                 &ccdr.clocks,
             );
@@ -946,7 +941,6 @@ pub fn setup(
 
             pounder::timestamp::Timestamper::new(
                 timestamp_timer,
-                dma2_streams.0,
                 tim8_channels.ch1,
                 &mut sampling_timer,
                 etr_pin,

src/hardware/dac.rs

@@ -52,13 +52,13 @@
 ///! served promptly after the transfer completes.
 use stm32h7xx_hal as hal;
 
-use super::design_parameters::SAMPLE_BUFFER_SIZE;
+use super::design_parameters::{SampleBuffer, SAMPLE_BUFFER_SIZE};
 use super::timers;
 
 use hal::dma::{
     dma::{DMAReq, DmaConfig},
     traits::TargetAddress,
-    MemoryToPeripheral, Transfer,
+    DMAError, MemoryToPeripheral, Transfer,
 };
 
 // The following global buffers are used for the DAC code DMA transfers. Two buffers are used for
@@ -66,14 +66,14 @@ use hal::dma::{
 // processed). Note that the contents of AXI SRAM is uninitialized, so the buffer contents on
 // startup are undefined. The dimensions are `ADC_BUF[adc_index][ping_pong_index][sample_index]`.
 #[link_section = ".axisram.buffers"]
-static mut DAC_BUF: [[[u16; SAMPLE_BUFFER_SIZE]; 3]; 2] =
+static mut DAC_BUF: [[SampleBuffer; 2]; 2] = [[[0; SAMPLE_BUFFER_SIZE]; 2]; 2];
-    [[[0; SAMPLE_BUFFER_SIZE]; 3]; 2];
 
 /// Custom type for referencing DAC output codes.
 /// The internal integer is the raw code written to the DAC output register.
 #[derive(Copy, Clone)]
 pub struct DacCode(pub u16);
 
+#[allow(clippy::from_over_into)]
 impl Into<f32> for DacCode {
     fn into(self) -> f32 {
         // The DAC output range in bipolar mode (including the external output op-amp) is +/- 4.096
@@ -105,7 +105,7 @@ macro_rules! dac_output {
                 _channel: timers::tim2::$trigger_channel,
                 spi: hal::spi::Spi<hal::stm32::$spi, hal::spi::Disabled, u16>,
             ) -> Self {
-                Self { _channel, spi }
+                Self { spi, _channel }
             }
 
             /// Start the SPI and begin operating in a DMA-driven transfer mode.
@@ -137,13 +137,12 @@ macro_rules! dac_output {
 
         /// Represents data associated with DAC.
         pub struct $name {
-            next_buffer: Option<&'static mut [u16; SAMPLE_BUFFER_SIZE]>,
             // Note: SPI TX functionality may not be used from this structure to ensure safety with DMA.
             transfer: Transfer<
                 hal::dma::dma::$data_stream<hal::stm32::DMA1>,
                 $spi,
                 MemoryToPeripheral,
-                &'static mut [u16; SAMPLE_BUFFER_SIZE],
+                &'static mut SampleBuffer,
                 hal::dma::DBTransfer,
             >,
         }
@@ -198,33 +197,26 @@ macro_rules! dac_output {
                         trigger_config,
                     );
 
-                Self {
+                Self { transfer }
-                    transfer,
-                    // Note(unsafe): This buffer is only used once and provided for the next DMA transfer.
-                    next_buffer: unsafe { Some(&mut DAC_BUF[$index][2]) },
-                }
             }
 
             pub fn start(&mut self) {
                 self.transfer.start(|spi| spi.start_dma());
             }
 
-            /// Acquire the next output buffer to populate it with DAC codes.
+            /// Wait for the transfer of the currently active buffer to complete,
-            pub fn acquire_buffer(&mut self) -> &mut [u16; SAMPLE_BUFFER_SIZE] {
+            /// then call a function on the now inactive buffer and acknowledge the
-                // Note: If a device hangs up, check that this conditional is passing correctly, as
+            /// transfer complete flag.
-                // there is no time-out checks here in the interest of execution speed.
+            ///
-                while !self.transfer.get_transfer_complete_flag() {}
+            /// NOTE(unsafe): Memory safety and access ordering is not guaranteed
-
+            /// (see the HAL DMA docs).
-                let next_buffer = self.next_buffer.take().unwrap();
+            pub fn with_buffer<F, R>(&mut self, f: F) -> Result<R, DMAError>
-
+            where
-                // Start the next transfer.
+                F: FnOnce(&mut SampleBuffer) -> R,
-                let (prev_buffer, _, _) =
+            {
-                    self.transfer.next_transfer(next_buffer).unwrap();
+                unsafe {
-
+                    self.transfer.next_dbm_transfer_with(|buf, _current| f(buf))
-                // .unwrap_none() https://github.com/rust-lang/rust/issues/62633
+                }
-                self.next_buffer.replace(prev_buffer);
-
-                self.next_buffer.as_mut().unwrap()
             }
         }
     };

src/hardware/design_parameters.rs

@@ -50,5 +50,7 @@ pub const ADC_SAMPLE_TICKS: u16 = 1 << ADC_SAMPLE_TICKS_LOG2;
 pub const SAMPLE_BUFFER_SIZE_LOG2: u8 = 3;
 pub const SAMPLE_BUFFER_SIZE: usize = 1 << SAMPLE_BUFFER_SIZE_LOG2;
 
+pub type SampleBuffer = [u16; SAMPLE_BUFFER_SIZE];
+
 // The MQTT broker IPv4 address
 pub const MQTT_BROKER: [u8; 4] = [10, 34, 16, 10];

src/hardware/pounder/attenuators.rs

@@ -30,16 +30,16 @@ pub trait AttenuatorInterface {
         // Read all the channels, modify the channel of interest, and write all the channels back.
         // This ensures the staging register and the output register are always in sync.
         let mut channels = [0_u8; 4];
-        self.read_all_attenuators(&mut channels)?;
+        self.transfer_attenuators(&mut channels)?;
 
         // The lowest 2 bits of the 8-bit shift register on the attenuator are ignored. Shift the
         // attenuator code into the upper 6 bits of the register value. Note that the attenuator
         // treats inputs as active-low, so the code is inverted before writing.
-        channels[channel as usize] = (!attenuation_code) << 2;
+        channels[channel as usize] = !(attenuation_code << 2);
-        self.write_all_attenuators(&channels)?;
+        self.transfer_attenuators(&mut channels)?;
 
         // Finally, latch the output of the updated channel to force it into an active state.
-        self.latch_attenuators(channel)?;
+        self.latch_attenuator(channel)?;
 
         Ok(attenuation_code as f32 / 2.0)
     }
@@ -57,8 +57,8 @@ pub trait AttenuatorInterface {
         // Reading the data always shifts data out of the staging registers, so we perform a
         // duplicate write-back to ensure the staging register is always equal to the output
         // register.
-        self.read_all_attenuators(&mut channels)?;
+        self.transfer_attenuators(&mut channels)?;
-        self.write_all_attenuators(&channels)?;
+        self.transfer_attenuators(&mut channels)?;
 
         // The attenuation code is stored in the upper 6 bits of the register, where each LSB
         // represents 0.5 dB. The attenuator stores the code as active-low, so inverting the result
@@ -74,13 +74,10 @@ pub trait AttenuatorInterface {
 
     fn reset_attenuators(&mut self) -> Result<(), Error>;
 
-    fn latch_attenuators(&mut self, channel: Channel) -> Result<(), Error>;
+    fn latch_attenuator(&mut self, channel: Channel) -> Result<(), Error>;
-    fn read_all_attenuators(
+
+    fn transfer_attenuators(
         &mut self,
         channels: &mut [u8; 4],
     ) -> Result<(), Error>;
-    fn write_all_attenuators(
-        &mut self,
-        channels: &[u8; 4],
-    ) -> Result<(), Error>;
 }

src/hardware/pounder/dds_output.rs

@@ -52,9 +52,11 @@
 ///! compile-time-known register update sequence needed for the application, the serialization
 ///! process can be done once and then register values can be written into a pre-computed serialized
 ///! buffer to avoid the software overhead of much of the serialization process.
+use log::warn;
+use stm32h7xx_hal as hal;
+
 use super::{hrtimer::HighResTimerE, QspiInterface};
 use ad9959::{Channel, DdsConfig, ProfileSerializer};
-use stm32h7xx_hal as hal;
 
 /// The DDS profile update stream.
 pub struct DdsOutput {

src/hardware/pounder/mod.rs

@@ -15,14 +15,21 @@ pub use dds_output::*;
 pub use hrtimer::{Channel as HRTimerChannel, *};
 pub use rf_power::*;
 
-const EXT_CLK_SEL_PIN: u8 = 8 + 7;
+pub enum GpioPin {
-#[allow(dead_code)]
+    Led4Green = 0,
-const OSC_EN_N_PIN: u8 = 8 + 6;
+    Led5Red = 1,
-const ATT_RST_N_PIN: u8 = 8 + 5;
+    Led6Green = 2,
-const ATT_LE3_PIN: u8 = 8 + 3;
+    Led7Red = 3,
-const ATT_LE2_PIN: u8 = 8 + 2;
+    Led8Green = 4,
-const ATT_LE1_PIN: u8 = 8 + 1;
+    Led9Red = 5,
-const ATT_LE0_PIN: u8 = 8;
+    AttLe0 = 8,
+    AttLe1 = 8 + 1,
+    AttLe2 = 8 + 2,
+    AttLe3 = 8 + 3,
+    AttRstN = 8 + 5,
+    OscEnN = 8 + 6,
+    ExtClkSel = 8 + 7,
+}
 
 #[derive(Debug, Copy, Clone)]
 pub enum Error {
@@ -35,13 +42,15 @@ pub enum Error {
     Adc,
 }
 
+/// The numerical value (discriminant) of the Channel enum is the index in the attenuator shift
+/// register as well as the attenuator latch enable signal index on the GPIO extender.
 #[derive(Debug, Copy, Clone)]
 #[allow(dead_code)]
 pub enum Channel {
-    In0,
+    In0 = 0,
-    In1,
+    Out0 = 1,
-    Out0,
+    In1 = 2,
-    Out1,
+    Out1 = 3,
 }
 
 #[derive(Serialize, Deserialize, Copy, Clone, Debug)]
@@ -78,14 +87,14 @@ pub struct DdsClockConfig {
     pub external_clock: bool,
 }
 
-impl Into<ad9959::Channel> for Channel {
+impl From<Channel> for ad9959::Channel {
     /// Translate pounder channels to DDS output channels.
-    fn into(self) -> ad9959::Channel {
+    fn from(other: Channel) -> Self {
-        match self {
+        match other {
-            Channel::In0 => ad9959::Channel::Two,
+            Channel::In0 => Self::Two,
-            Channel::In1 => ad9959::Channel::Four,
+            Channel::In1 => Self::Four,
-            Channel::Out0 => ad9959::Channel::One,
+            Channel::Out0 => Self::One,
-            Channel::Out1 => ad9959::Channel::Three,
+            Channel::Out1 => Self::Three,
         }
     }
 }
@@ -298,25 +307,20 @@ impl PounderDevices {
             adc2_in_p,
         };
 
-        // Configure power-on-default state for pounder. All LEDs are on, on-board oscillator
+        // Configure power-on-default state for pounder. All LEDs are off, on-board oscillator
-        // selected, attenuators out of reset. Note that testing indicates the output state needs to
+        // selected and enabled, attenuators out of reset. Note that testing indicates the
-        // be set first to properly update the output registers.
+        // output state needs to be set first to properly update the output registers.
         devices
             .mcp23017
             .all_pin_mode(mcp23017::PinMode::OUTPUT)
             .map_err(|_| Error::I2c)?;
         devices
             .mcp23017
-            .write_gpio(mcp23017::Port::GPIOA, 0x3F)
+            .write_gpio(mcp23017::Port::GPIOA, 0x00)
             .map_err(|_| Error::I2c)?;
         devices
             .mcp23017
-            .write_gpio(mcp23017::Port::GPIOB, 1 << 5)
+            .write_gpio(mcp23017::Port::GPIOB, 0x2F)
-            .map_err(|_| Error::I2c)?;
-
-        devices
-            .mcp23017
-            .digital_write(EXT_CLK_SEL_PIN, false)
             .map_err(|_| Error::I2c)?;
 
         Ok(devices)
@@ -327,12 +331,11 @@ impl AttenuatorInterface for PounderDevices {
     /// Reset all of the attenuators to a power-on default state.
     fn reset_attenuators(&mut self) -> Result<(), Error> {
         self.mcp23017
-            .digital_write(ATT_RST_N_PIN, false)
+            .write_gpio(mcp23017::Port::GPIOB, 0x0f)
             .map_err(|_| Error::I2c)?;
-        // TODO: Measure the I2C transaction speed to the RST pin to ensure that the delay is
+        // Duration of one I2C transaction is sufficiently long.
-        // sufficient. Document the delay here.
         self.mcp23017
-            .digital_write(ATT_RST_N_PIN, true)
+            .write_gpio(mcp23017::Port::GPIOB, 0x2f)
             .map_err(|_| Error::I2c)?;
 
         Ok(())
@@ -342,31 +345,24 @@ impl AttenuatorInterface for PounderDevices {
     ///
     /// Args:
     /// * `channel` - The attenuator channel to latch.
-    fn latch_attenuators(&mut self, channel: Channel) -> Result<(), Error> {
+    fn latch_attenuator(&mut self, channel: Channel) -> Result<(), Error> {
-        let pin = match channel {
+        let pin = channel as u8;
-            Channel::In0 => ATT_LE0_PIN,
-            Channel::In1 => ATT_LE2_PIN,
-            Channel::Out0 => ATT_LE1_PIN,
-            Channel::Out1 => ATT_LE3_PIN,
-        };
-
         self.mcp23017
-            .digital_write(pin, true)
+            .write_gpio(mcp23017::Port::GPIOB, 0x2f & !(1 << pin))
             .map_err(|_| Error::I2c)?;
-        // TODO: Measure the I2C transaction speed to the RST pin to ensure that the delay is
+        // Duration of one I2C transaction is sufficiently long.
-        // sufficient. Document the delay here.
         self.mcp23017
-            .digital_write(pin, false)
+            .write_gpio(mcp23017::Port::GPIOB, 0x2f)
             .map_err(|_| Error::I2c)?;
-
         Ok(())
     }
 
     /// Read the raw attenuation codes stored in the attenuator shift registers.
     ///
     /// Args:
-    /// * `channels` - A slice to store the channel readings into.
+    /// * `channels` - A 4 byte slice to be shifted into the
-    fn read_all_attenuators(
+    ///     attenuators and to contain the data shifted out.
+    fn transfer_attenuators(
         &mut self,
         channels: &mut [u8; 4],
     ) -> Result<(), Error> {
@@ -376,23 +372,6 @@ impl AttenuatorInterface for PounderDevices {
 
         Ok(())
     }
-
-    /// Write the attenuator shift registers.
-    ///
-    /// Args:
-    /// * `channels` - The data to write into the attenuators.
-    fn write_all_attenuators(
-        &mut self,
-        channels: &[u8; 4],
-    ) -> Result<(), Error> {
-        let mut result = [0_u8; 4];
-        result.clone_from_slice(channels);
-        self.attenuator_spi
-            .transfer(&mut result)
-            .map_err(|_| Error::Spi)?;
-
-        Ok(())
-    }
 }
 
 impl PowerMeasurementInterface for PounderDevices {

src/hardware/pounder/rf_power.rs

@@ -1,20 +1,22 @@
 use super::{Channel, Error};
 
-/// Provide an interface to measure RF input power in dB.
+/// Provide an interface to measure RF input power in dBm.
 pub trait PowerMeasurementInterface {
     fn sample_converter(&mut self, channel: Channel) -> Result<f32, Error>;
 
     /// Measure the power of an input channel in dBm.
     ///
-    /// Note: This function assumes the input channel is connected to an AD8363 output.
-    ///
     /// Args:
-    /// * `channel` - The pounder channel to measure the power of in dBm.
+    /// * `channel` - The pounder input channel to measure the power of.
+    ///
+    /// Returns:
+    /// Power in dBm after the digitally controlled attenuator before the amplifier.
     fn measure_power(&mut self, channel: Channel) -> Result<f32, Error> {
         let analog_measurement = self.sample_converter(channel)?;
 
-        // The AD8363 with VSET connected to VOUT provides an output voltage of 51.7mV / dB at
+        // The AD8363 with VSET connected to VOUT provides an output voltage of 51.7 mV/dB at
-        // 100MHz. It also indicates  a y-intercept of -58dBm.
+        // 100MHz with an intercept of -58 dBm.
-        Ok(analog_measurement / 0.0517 - 58.0)
+        // It is placed behind a 20 dB tap.
+        Ok(analog_measurement * (1. / 0.0517) + (-58. + 20.))
     }
 }

src/hardware/pounder/timestamp.rs

@@ -13,50 +13,24 @@
 ///! Once the timer is configured, an input capture is configured to record the timer count
 ///! register. The input capture is configured to utilize an internal trigger for the input capture.
 ///! The internal trigger is selected such that when a sample is generated on ADC0, the input
-///! capture is simultaneously triggered. This results in the input capture triggering identically
+///! capture is simultaneously triggered. That trigger is prescaled (its rate is divided) by the
-///! to when the ADC samples the input.
+///! batch size. This results in the input capture triggering identically to when the ADC samples
-///!
+///! the last sample of the batch. That sample is then available for processing by the user.
-///! Once the input capture is properly configured, a DMA transfer is configured to collect all of
+use crate::hardware::{design_parameters, timers};
-///! timestamps. The DMA transfer collects 1 timestamp for each ADC sample collected. In order to
+use core::convert::TryFrom;
-///! avoid potentially losing a timestamp for a sample, the DMA transfer operates in double-buffer
-///! mode. As soon as the DMA transfer completes, the hardware automatically swaps over to a second
-///! buffer to continue capturing. This alleviates timing sensitivities of the DMA transfer
-///! schedule.
 use stm32h7xx_hal as hal;
 
-use hal::dma::{dma::DmaConfig, PeripheralToMemory, Transfer};
-
-use crate::hardware::{design_parameters::SAMPLE_BUFFER_SIZE, timers};
-
-// Three buffers are required for double buffered mode - 2 are owned by the DMA stream and 1 is the
-// working data provided to the application. These buffers must exist in a DMA-accessible memory
-// region. Note that AXISRAM is not initialized on boot, so their initial contents are undefined.
-#[link_section = ".axisram.buffers"]
-static mut BUF: [[u16; SAMPLE_BUFFER_SIZE]; 3] = [[0; SAMPLE_BUFFER_SIZE]; 3];
-
 /// Software unit to timestamp stabilizer ADC samples using an external pounder reference clock.
 pub struct Timestamper {
-    next_buffer: Option<&'static mut [u16; SAMPLE_BUFFER_SIZE]>,
     timer: timers::PounderTimestampTimer,
-    transfer: Transfer<
+    capture_channel: timers::tim8::Channel1InputCapture,
-        hal::dma::dma::Stream0<hal::stm32::DMA2>,
-        timers::tim8::Channel1InputCapture,
-        PeripheralToMemory,
-        &'static mut [u16; SAMPLE_BUFFER_SIZE],
-        hal::dma::DBTransfer,
-    >,
 }
 
 impl Timestamper {
     /// Construct the pounder sample timestamper.
     ///
-    /// # Note
-    /// The DMA is immediately configured after instantiation. It will not collect any samples
-    /// until the sample timer begins to cause input capture triggers.
-    ///
     /// # Args
     /// * `timestamp_timer` - The timer peripheral used for capturing timestamps from.
-    /// * `stream` - The DMA stream to use for collecting timestamps.
     /// * `capture_channel` - The input capture channel for collecting timestamps.
     /// * `sampling_timer` - The stabilizer ADC sampling timer.
     /// * `_clock_input` - The input pin for the external clock from Pounder.
@@ -65,18 +39,12 @@ impl Timestamper {
     /// The new pounder timestamper in an operational state.
     pub fn new(
         mut timestamp_timer: timers::PounderTimestampTimer,
-        stream: hal::dma::dma::Stream0<hal::stm32::DMA2>,
         capture_channel: timers::tim8::Channel1,
         sampling_timer: &mut timers::SamplingTimer,
         _clock_input: hal::gpio::gpioa::PA0<
             hal::gpio::Alternate<hal::gpio::AF3>,
         >,
     ) -> Self {
-        let config = DmaConfig::default()
-            .memory_increment(true)
-            .circular_buffer(true)
-            .double_buffer(true);
-
         // The sampling timer should generate a trigger output when CH1 comparison occurs.
         sampling_timer.generate_trigger(timers::TriggerGenerator::ComparePulse);
 
@@ -85,64 +53,39 @@ impl Timestamper {
         timestamp_timer.set_trigger_source(timers::TriggerSource::Trigger1);
 
         // The capture channel should capture whenever the trigger input occurs.
-        let input_capture = capture_channel
+        let mut input_capture = capture_channel
             .into_input_capture(timers::tim8::CaptureSource1::TRC);
-        input_capture.listen_dma();
 
-        // The data transfer is always a transfer of data from the peripheral to a RAM buffer.
+        // Capture at the batch period.
-        let data_transfer: Transfer<_, _, PeripheralToMemory, _, _> =
+        input_capture.configure_prescaler(
-            Transfer::init(
+            timers::Prescaler::try_from(
-                stream,
+                design_parameters::SAMPLE_BUFFER_SIZE_LOG2,
-                input_capture,
+            )
-                // Note(unsafe): BUF[0] and BUF[1] are "owned" by this peripheral.
+            .unwrap(),
-                // They shall not be used anywhere else in the module.
+        );
-                unsafe { &mut BUF[0] },
-                unsafe { Some(&mut BUF[1]) },
-                config,
-            );
 
         Self {
             timer: timestamp_timer,
-            transfer: data_transfer,
+            capture_channel: input_capture,
-
-            // Note(unsafe): BUF[2] is "owned" by this peripheral. It shall not be used anywhere
-            // else in the module.
-            next_buffer: unsafe { Some(&mut BUF[2]) },
         }
     }
 
-    /// Start the DMA transfer for collecting timestamps.
+    /// Start collecting timestamps.
-    #[allow(dead_code)]
     pub fn start(&mut self) {
-        self.transfer
+        self.capture_channel.enable();
-            .start(|capture_channel| capture_channel.enable());
     }
 
     /// Update the period of the underlying timestamp timer.
-    #[allow(dead_code)]
     pub fn update_period(&mut self, period: u16) {
         self.timer.set_period_ticks(period);
     }
 
-    /// Obtain a buffer filled with timestamps.
+    /// Obtain a timestamp.
     ///
     /// # Returns
-    /// A reference to the underlying buffer that has been filled with timestamps.
+    /// A `Result` potentially indicating capture overflow and containing a `Option` of a captured
-    #[allow(dead_code)]
+    /// timestamp.
-    pub fn acquire_buffer(&mut self) -> &[u16; SAMPLE_BUFFER_SIZE] {
+    pub fn latest_timestamp(&mut self) -> Result<Option<u16>, Option<u16>> {
-        // Wait for the transfer to fully complete before continuing.
+        self.capture_channel.latest_capture()
-        // Note: If a device hangs up, check that this conditional is passing correctly, as there is
-        // no time-out checks here in the interest of execution speed.
-        while !self.transfer.get_transfer_complete_flag() {}
-
-        let next_buffer = self.next_buffer.take().unwrap();
-
-        // Start the next transfer.
-        let (prev_buffer, _, _) =
-            self.transfer.next_transfer(next_buffer).unwrap();
-
-        self.next_buffer.replace(prev_buffer); // .unwrap_none() https://github.com/rust-lang/rust/issues/62633
-
-        self.next_buffer.as_ref().unwrap()
     }
 }

src/hardware/timers.rs

@@ -1,5 +1,6 @@
 ///! The sampling timer is used for managing ADC sampling and external reference timestamping.
 use super::hal;
+use num_enum::TryFromPrimitive;
 
 use hal::stm32::{
     // TIM1 and TIM8 have identical registers.
@@ -34,6 +35,8 @@ pub enum TriggerSource {
 
 /// Prescalers for externally-supplied reference clocks.
 #[allow(dead_code)]
+#[derive(TryFromPrimitive)]
+#[repr(u8)]
 pub enum Prescaler {
     Div1 = 0b00,
     Div2 = 0b01,
@@ -353,6 +356,21 @@ macro_rules! timer_channels {
                     let regs = unsafe { &*<$TY>::ptr() };
                     regs.[< $ccmrx _input >]().modify(|_, w| w.[< ic $index f >]().bits(filter as u8));
                 }
+
+                /// Configure the input capture prescaler.
+                ///
+                /// # Args
+                /// * `psc` - Prescaler exponent.
+                #[allow(dead_code)]
+                pub fn configure_prescaler(&mut self, prescaler: super::Prescaler) {
+                    // Note(unsafe): This channel owns all access to the specific timer channel.
+                    // Only atomic operations on completed on the timer registers.
+                    let regs = unsafe { &*<$TY>::ptr() };
+                    // Note(unsafe): Enum values are all valid.
+                    #[allow(unused_unsafe)]
+                    regs.[< $ccmrx _input >]().modify(|_, w| unsafe {
+                        w.[< ic $index psc >]().bits(prescaler as u8)});
+                }
             }
 
             // Note(unsafe): This manually implements DMA support for input-capture channels. This

src/lib.rs

@@ -1,8 +1,18 @@
 #![no_std]
 #![cfg_attr(feature = "nightly", feature(core_intrinsics))]
 
-#[macro_use]
-extern crate log;
-
 pub mod hardware;
 pub mod net;
+
+/// Macro to reduce rightward drift when calling the same closure-based API
+/// on multiple structs simultaneously, e.g. when accessing DMA buffers.
+/// This could be improved a bit using the tuple-based style from `mutex-trait`.
+#[macro_export]
+macro_rules! flatten_closures {
+    ($fn:ident, $e:ident, $fun:block) => {
+        $e.$fn(|$e| $fun ).unwrap()
+    };
+    ($fn:ident, $e:ident, $($es:ident),+, $fun:block) => {
+        $e.$fn(|$e| flatten_closures!($fn, $($es),*, $fun)).unwrap()
+    };
+}

src/net/miniconf_client.rs

@@ -11,6 +11,7 @@
 ///! Respones to settings updates are sent without quality-of-service guarantees, so there's no
 ///! guarantee that the requestee will be informed that settings have been applied.
 use heapless::String;
+use log::info;
 
 use super::{MqttMessage, NetworkReference, SettingsResponse, UpdateState};
 use crate::hardware::design_parameters::MQTT_BROKER;
@@ -102,7 +103,7 @@ where
             let path = match topic.strip_prefix(prefix) {
                 // For paths, we do not want to include the leading slash.
                 Some(path) => {
-                    if path.len() > 0 {
+                    if !path.is_empty() {
                         &path[1..]
                     } else {
                         path
@@ -116,9 +117,8 @@ where
 
             let message: SettingsResponse = settings
                 .string_set(path.split('/').peekable(), message)
-                .and_then(|_| {
+                .map(|_| {
                     update = true;
-                    Ok(())
                 })
                 .into();