succd: factor out ringbuffer, do not recalculate average on every request

succbone/succd/main.go

@@ -28,6 +28,8 @@ func main() {
 
 	d := daemon{}
 	d.daemonState.rpOn = true
+	d.daemonState.piraniVolts3.limit = 3
+	d.daemonState.piraniVolts100.limit = 100
 
 	d.aboveRough.threshold = float64(flagPressureThresholdRough)
 	d.aboveHigh.threshold = float64(flagPressureThresholdHigh)

succbone/succd/process.go

@@ -66,6 +66,33 @@ func (t *thresholdOutput) process(value float64) {
 	}
 }
 
+// ringbufferInput accumulates analog data up to limit samples, and calculates
+// an average.
+type ringbufferInput struct {
+	data  []float32
+	limit uint
+	avg   float32
+}
+
+func (r *ringbufferInput) process(input float32) {
+	// TODO(q3k): use actual ringbuffer
+	// TODO(q3k): optimize average calculation
+	// TODO(q3k): precalculate value in mbar
+	r.data = append(r.data, input)
+	trim := len(r.data) - int(r.limit)
+	if trim > 0 {
+		r.data = r.data[trim:]
+	}
+	avg := float32(0.0)
+	for _, v := range r.data {
+		avg += v
+	}
+	if len(r.data) != 0 {
+		avg /= float32(len(r.data))
+	}
+	r.avg = avg
+}
+
 // process runs the pain acquisition and control loop of succd.
 func (d *daemon) process(ctx context.Context) {
 	ticker := time.NewTicker(time.Millisecond * 100)
@@ -96,12 +123,9 @@ func (d *daemon) processOnce(_ context.Context) error {
 	d.mu.Lock()
 	defer d.mu.Unlock()
 
-	// Process pirani ringbuffer.
-	d.adcPiraniVolts = append(d.adcPiraniVolts, v)
-	trim := len(d.adcPiraniVolts) - 100
-	if trim > 0 {
-		d.adcPiraniVolts = d.adcPiraniVolts[trim:]
-	}
+	// Process pirani ringbuffers.
+	d.piraniVolts3.process(v)
+	d.piraniVolts100.process(v)
 
 	d.pumpdown.process()
 	d.vent.process()

succbone/succd/process_state.go

@@ -7,11 +7,11 @@ import "math"
 type daemonState struct {
 	safety safetyStatus
 
-	// adcPiraniVolts is a moving window of read ADC values, used to calculate a
-	// moving average.
-	adcPiraniVolts []float32
-	rpOn           bool
-	dpOn           bool
+	piraniVolts100 ringbufferInput
+	piraniVolts3   ringbufferInput
+
+	rpOn bool
+	dpOn bool
 
 	vent       momentaryOutput
 	pumpdown   momentaryOutput
@@ -42,20 +42,18 @@ const (
 	piraniDetectionDisconnected = iota
 )
 
+func piraniVoltsToMbar(v float32) float32 {
+	// Per Pirani probe docs.
+	bar := math.Pow(10.0, float64(v)-8.5)
+	return float32(bar * 1000.0)
+}
+
 // piraniDetection guesses whether the pirani gauge is connected.
 func (d *daemonState) piraniDetection() piraniDetection {
-	if len(d.adcPiraniVolts) < 3 {
+	if len(d.piraniVolts3.data) < int(d.piraniVolts3.limit) {
 		return piraniDetectionUnknown
 	}
-	volts := float32(0.0)
-	for _, v := range d.adcPiraniVolts[len(d.adcPiraniVolts)-3:] {
-		volts += v
-	}
-	volts /= 3.0
-
-	bar := math.Pow(10.0, float64(volts)-8.5)
-	mbar := float32(bar * 1000.0)
-
+	mbar := piraniVoltsToMbar(d.piraniVolts3.avg)
 	if mbar < 4e-6 {
 		return piraniDetectionDisconnected
 	}
@@ -63,17 +61,8 @@ func (d *daemonState) piraniDetection() piraniDetection {
 }
 
 func (d *daemonState) pirani() (volts float32, mbar float32) {
-	volts = 0.0
-	for _, v := range d.adcPiraniVolts {
-		volts += v
-	}
-	if len(d.adcPiraniVolts) != 0 {
-		volts /= float32(len(d.adcPiraniVolts))
-	}
-
-	// Per Pirani probe docs.
-	bar := math.Pow(10.0, float64(volts)-8.5)
-	mbar = float32(bar * 1000.0)
+	volts = d.piraniVolts100.avg
+	mbar = piraniVoltsToMbar(volts)
 	return
 }