cleanup, robustify

README.md

@@ -9,14 +9,20 @@
 * dual channel
 * SPI ADC
 * SPI DAC
-* fixed AFE gains
-* 500 kHz rate, timed
-* < 2 µs latency, unmatched
+* 500 kHz rate, timed sampling
+* 2 µs latency, unmatched between channels
 * f32 IIR math
 * generic biquad (second order) IIR filter
 * anti-windup
 * derivative kick avoidance
-* configurable output limits
+
+## Limitations/TODOs
+
+* Fixed AFE gains
+* The IP and MAC address are [hardcoded](src/main.rs)
+* Expose configurable limits
+* 100Base-T only
+* Digital IO, GPIO header, AFE header, EEM header are not handled
 
 ## Hardware
 
@@ -33,3 +39,10 @@ See https://github.com/sinara-hw/Stabilizer
 * `rustup target add thumbv7em-none-eabihf`
 * `openocd -f stabilizer.cfg` and leave it running
 * `cargo run --release`
+
+
+## Protocol
+
+Stabilizer can be configured via newline-delimited JSON over TCP.
+It listens on port 1235. [stabilizer.py](stabilizer.py) contains a reference
+implementation of the protocol.

src/iir.rs

@@ -39,6 +39,7 @@ fn macc<T>(y0: T, x: &[T], a: &[T]) -> T
     x.iter().zip(a.iter()).map(|(&i, &j)| i * j).fold(y0, |y, xa| y + xa)
 }
 
+#[allow(unused)]
 impl IIR {
     pub fn set_pi(&mut self, kp: f32, ki: f32, g: f32) -> Result<(), &str> {
         let ki = copysign(ki, kp);

src/main.rs

@@ -692,7 +692,7 @@ fn main() -> ! {
 
 #[derive(Deserialize,Serialize)]
 struct Request {
-    channel: i8,
+    channel: u8,
     iir: IIR,
 }
 
@@ -731,10 +731,14 @@ fn handle_command(socket: &mut net::socket::TcpSocket) {
             } else {
                 match from_slice::<Request>(&data) {
                     Ok(request) => {
+                        if request.channel > 1 {
+                            Response{ code: 500, message: "invalid channel" }
+                        } else {
                             cortex_m::interrupt::free(|_| {
                                 unsafe { IIR_CH[request.channel as usize] = request.iir; };
                             });
                             Response{ code: 200, message: "ok" }
+                        }
                     },
                     Err(err) => {
                         warn!("parse error {}", err);

stabilizer.py

@@ -32,12 +32,13 @@ class StabilizerConfig:
 
 class IIR:
     t_update = 2e-6
+    full_scale = float((1 << 15) - 1)
 
     def __init__(self):
         self.ba = np.zeros(5, np.float32)
         self.y_offset = 0.
-        self.y_min = -float(1 << 15)
-        self.y_max = float(1 << 15) - 1
+        self.y_min = -self.full_scale - 1
+        self.y_max = self.full_scale
 
     def as_dict(self):
         iir = OD()
@@ -70,7 +71,7 @@ class IIR:
         self.ba[4] = 0.
 
     def set_x_offset(self, o):
-        b = self.ba[:3].sum()*((1 << 15) - 1)
+        b = self.ba[:3].sum()*self.full_scale
         self.y_offset = b*o
 
 
@@ -100,6 +101,7 @@ if __name__ == "__main__":
         i.set_x_offset(args.offset)
         s = StabilizerConfig()
         await s.connect(args.stabilizer)
+        assert args.channel in range(2)
         r = await s.set(args.channel, i)
 
     loop.run_until_complete(main())