adc: don't calibrate but convert using ChannelCalibration

src/ad7172/adc.rs

@@ -114,27 +114,11 @@ impl<SPI: Transfer<u8, Error = E>, NSS: OutputPin, E: fmt::Debug> Adc<SPI, NSS>
         Ok(())
     }
 
-    /// Calibrates offset registers
+    pub fn get_calibration(&mut self, index: u8) -> Result<ChannelCalibration, SPI::Error> {
-    pub fn calibrate(&mut self) -> Result<(), SPI::Error> {
+        let offset = self.read_reg(&regs::Offset { index })?.offset();
-        // internal offset calibration
+        let gain = self.read_reg(&regs::Gain { index })?.gain();
-        self.update_reg(&regs::AdcMode, |adc_mode| {
+        let bipolar = self.read_reg(&regs::SetupCon { index })?.bipolar();
-            adc_mode.set_mode(Mode::InternalOffsetCalibration);
+        Ok(ChannelCalibration { offset, gain, bipolar })
-        })?;
-        while ! self.read_reg(&regs::Status)?.ready() {}
-
-        // system offset calibration
-        self.update_reg(&regs::AdcMode, |adc_mode| {
-            adc_mode.set_mode(Mode::SystemOffsetCalibration);
-        })?;
-        while ! self.read_reg(&regs::Status)?.ready() {}
-
-        // system gain calibration
-        self.update_reg(&regs::AdcMode, |adc_mode| {
-            adc_mode.set_mode(Mode::SystemGainCalibration);
-        })?;
-        while ! self.read_reg(&regs::Status)?.ready() {}
-
-        Ok(())
     }
 
     pub fn start_continuous_conversion(&mut self) -> Result<(), SPI::Error> {
@@ -279,3 +263,26 @@ impl<SPI: Transfer<u8, Error = E>, NSS: OutputPin, E: fmt::Debug> Adc<SPI, NSS>
         result
     }
 }
+
+#[derive(Debug, Clone)]
+pub struct ChannelCalibration {
+    offset: u32,
+    gain: u32,
+    bipolar: bool,
+}
+
+impl ChannelCalibration {
+    pub fn convert_data(&self, data: u32) -> f64 {
+        let data = if self.bipolar {
+            (data as i32 - 0x80_0000) as f64
+        } else {
+            data as f64 / 2.0
+        };
+        let data = data / (self.gain as f64 / (0x40_0000 as f64));
+        let data = data + (self.offset as i32 - 0x80_0000) as f64;
+        let data = data / (2 << 23) as f64;
+
+        const V_REF: f64 = 3.0;
+        data * V_REF / 0.75
+    }
+}

src/channels.rs

@@ -32,23 +32,16 @@ impl Channels {
         // Feature not used
         adc.set_sync_enable(false).unwrap();
 
-        // Calibrate ADC channels individually
-        adc.disable_all_channels().unwrap();
-
-        adc.setup_channel(0, ad7172::Input::Ain0, ad7172::Input::Ain1).unwrap();
-        adc.calibrate().unwrap();
-        adc.disable_channel(0).unwrap();
-
-        adc.setup_channel(1, ad7172::Input::Ain2, ad7172::Input::Ain3).unwrap();
-        adc.calibrate().unwrap();
-        adc.disable_channel(1).unwrap();
-
         // Setup channels and start ADC
         adc.setup_channel(0, ad7172::Input::Ain0, ad7172::Input::Ain1).unwrap();
         adc.setup_channel(1, ad7172::Input::Ain2, ad7172::Input::Ain3).unwrap();
         adc.start_continuous_conversion().unwrap();
 
-        Channels { channel0, channel1, adc, pins_adc, pwm }
+        let mut channels = Channels { channel0, channel1, adc, pins_adc, pwm };
+        for channel in 0..CHANNELS {
+            channels.calibrate_dac_value(channel);
+        }
+        channels
     }
 
     pub fn channel_state<I: Into<usize>>(&mut self, channel: I) -> &mut ChannelState {

src/main.rs

@@ -102,8 +102,10 @@ fn main() -> ! {
     leds.g4.off();
 
     let mut channels = Channels::new(pins);
-    channels.calibrate_dac_value(0);
+    let adc_calibration = [
-    channels.calibrate_dac_value(1);
+        channels.adc.get_calibration(0).unwrap(),
+        channels.adc.get_calibration(1).unwrap(),
+    ];
 
     #[cfg(not(feature = "generate-hwaddr"))]
     let hwaddr = EthernetAddress(NET_HWADDR);
@@ -162,12 +164,16 @@ fn main() -> ! {
 
                                             let state = channels.channel_state(channel);
                                             let _ = writeln!(
-                                                socket, "t={} adc_raw{}=0x{:06X} vref={} dac_feedback={} itec={} tec={} tec_u_meas={}",
+                                                socket, "channel {}: t={} adc_raw{}=0x{:06X} adc{}={:.3}V vref={} dac_feedback={} itec={} tec={} tec_u_meas={}",
+                                                channel,
                                                 state.adc_time, channel, adc_data,
+                                                channel, adc_calibration[channel].convert_data(adc_data),
                                                 vref, dac_feedback,
                                                 itec, tec_i,
                                                 tec_u_meas,
                                             );
+                                        } else {
+                                            let _ = writeln!(socket, "channel {}: no adc input", channel);
                                         }
                                     }
                                 }
@@ -373,9 +379,11 @@ fn main() -> ! {
                     } else if socket.can_send() && socket.send_capacity() - socket.send_queue() > 256 {
                         while let Some(channel) = session.is_report_pending() {
                             let state = &mut channels.channel_state(usize::from(channel));
+                            let adc_data = state.adc_data.unwrap_or(0);
                             let _ = writeln!(
-                                socket, "t={} raw{}=0x{:06X}",
+                                socket, "t={} raw{}=0x{:06X} value={:.3}V",
-                                state.adc_time, channel, state.adc_data.unwrap_or(0)
+                                state.adc_time, channel, adc_data,
+                                adc_calibration[channel].convert_data(adc_data),
                             ).map(|_| {
                                 session.mark_report_sent(channel);
                             });