succd: add additional safety interlocks

succbone/succd/main.go

@@ -31,6 +31,7 @@ func main() {
 	}
 	d.aboveRough.threshold = float64(flagPressureThresholdRough)
 	d.aboveHigh.threshold = float64(flagPressureThresholdHigh)
+  d.lastPressures = newRingbuffer()
 	if flagFake {
 		klog.Infof("Starting with fake peripherals")
 		d.adcPirani = &fakeADC{}

succbone/succd/process.go

@@ -17,7 +17,10 @@ type daemon struct {
 	// Pirani gauge.
 	adcPirani adc
 
+  lastPressures ringbuffer
+
 	failsafe     bool
+	highPressure bool
 
 	gpioDiffusionPump gpio
 	gpioRoughingPump  gpio
@@ -122,7 +125,15 @@ func (d *daemon) processOnce(_ context.Context) error {
 	d.aboveRough.process(float64(mbar))
 	d.aboveHigh.process(float64(mbar))
 
-	if mbar < 4e-6 {
+  d.lastPressures.AddValue(mbar)
+
+  // max rate of 1.0 in 500 ms because ringbuffer holds 5 values
+  if d.lastPressures.MaxMinDiff() > 1.0 {
+    if !d.failsafe {
+      d.failsafe = true
+			klog.Errorf("Pressure changed too fast; entering failsafe mode")
+    }
+  } else if mbar < 4e-6 {
 		// Unrealistic result, Pirani probe probably disconnected. Failsafe mode.
 		if !d.failsafe {
 			d.failsafe = true
@@ -131,13 +142,30 @@ func (d *daemon) processOnce(_ context.Context) error {
 	} else {
 		if d.failsafe {
 			d.failsafe = false
-			klog.Infof("Pirani probe has been reconnected; quitting failsafe mode")
+			klog.Infof("Values are plausible again; quitting failsafe mode")
+		}
+	}
+
+	if mbar >= 1e-1 {
+		if !d.highPressure {
+			d.highPressure = true
+			klog.Errorf("Pressure is too high; enabling diffusion pump lockout")
+		}
+	} else {
+		if d.highPressure {
+			d.highPressure = false
+      klog.Infof("Pressure is low enough for diffusion pump operation; quitting diffusion pump lockout")
 		}
 	}
 
 	if d.failsafe {
 		d.aboveRough.output = true
 		d.aboveHigh.output = true
+    d.dpOn = false
+	}
+
+	if d.highPressure {
+		d.dpOn = false
 	}
 
 	// Update relay outputs.

succbone/succd/ringbuffer.go

@@ -0,0 +1,34 @@
+package main
+
+type ringbuffer struct {
+  data  []float32
+  idx   int
+}
+
+func newRingbuffer() ringbuffer {
+  return ringbuffer {
+    data: make([]float32, 5),
+    idx: 0,
+  }
+}
+
+func (rb *ringbuffer) AddValue(value float32) {
+  rb.data[rb.idx] = value;
+  rb.idx = (rb.idx + 1) % len(rb.data)
+}
+
+func (rb *ringbuffer) MaxMinDiff() float32 {
+  min := rb.data[0]
+  max := rb.data[0]
+
+  for _, val := range rb.data {
+    if val < min {
+      min = val
+    }
+    if val > max {
+      max = val
+    }
+  }
+
+  return max - min
+}