More succd into succbone subdirectory

succbone/succd/adc.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// adc is an abstract ADC-based analog input.
+type adc interface {
+	// Read returns the ADC value in volts.
+	Read() (float32, error)
+}
+
+// bbADC implements adc using a BeagleBone's built-in ADC.
+type bbADC struct {
+	path string
+}
+
+// newBBADC returns a BeagleBone ADC for a given channel number.
+func newBBADC(num int) (*bbADC, error) {
+	path := fmt.Sprintf("/sys/bus/iio/devices/iio:device0/in_voltage%d_raw", num)
+	if _, err := os.Stat(path); err != nil {
+		return nil, fmt.Errorf("could not access: %w", err)
+	}
+	return &bbADC{
+		path: path,
+	}, nil
+}
+
+func (b *bbADC) Read() (float32, error) {
+	by, err := os.ReadFile(b.path)
+	if err != nil {
+		return 0, err
+	}
+	d := strings.TrimSpace(string(by))
+	v, err := strconv.ParseUint(d, 10, 64)
+	if err != nil {
+		return 0, err
+	}
+	// The ADC Vref/Vdd is at 1.8V and is 10-bit (0-4095).
+	vadc := float32(v) * 1.8 / 4096.0
+	// The ADC is connected through a resistor divider.
+	r1 := float32(1000.0)
+	r2 := float32(4698.0)
+	vin := vadc / (r1 / (r1 + r2))
+	return vin, nil
+}
+
+// fakeADC implements an adc that outputs a sine wave. This is used for testing.
+type fakeADC struct {
+}
+
+func (b *fakeADC) Read() (float32, error) {
+	t := float64(time.Now().UnixMilli()) / 1000
+	v := (math.Sin(t/10)+1)*(6.5/2) + 2
+	return float32(v), nil
+}