first push of

pi/roverd/brc.go

@@ -0,0 +1,83 @@
+package roverd
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strconv"
+	"time"
+)
+
+type BRCPulser struct {
+	cfg    BRCConfig
+	logger *log.Logger
+}
+
+func NewBRCPulser(cfg BRCConfig, logger *log.Logger) (*BRCPulser, error) {
+	if err := exportGPIO(cfg.GPIOPin); err != nil {
+		return nil, err
+	}
+	if err := writeGPIO(cfg.GPIOPin, "direction", []byte("out\n")); err != nil {
+		return nil, err
+	}
+	if err := writeGPIO(cfg.GPIOPin, "value", []byte("1\n")); err != nil {
+		return nil, err
+	}
+
+	return &BRCPulser{cfg: cfg, logger: logger}, nil
+}
+
+func (b *BRCPulser) Close() {
+	_ = writeGPIO(b.cfg.GPIOPin, "value", []byte("1\n"))
+	_ = unexportGPIO(b.cfg.GPIOPin)
+}
+
+func (b *BRCPulser) Start(ctx context.Context) {
+	go func() {
+		ticker := time.NewTicker(b.cfg.PulseEvery.Duration)
+		defer ticker.Stop()
+
+		for {
+			b.pulseOnce()
+			select {
+			case <-ctx.Done():
+				return
+			case <-ticker.C:
+			}
+		}
+	}()
+}
+
+func (b *BRCPulser) pulseOnce() {
+	if err := writeGPIO(b.cfg.GPIOPin, "value", []byte("0\n")); err != nil {
+		b.logger.Printf("brc pulse low: %v", err)
+		return
+	}
+	time.Sleep(b.cfg.PulseWidth.Duration)
+	if err := writeGPIO(b.cfg.GPIOPin, "value", []byte("1\n")); err != nil {
+		b.logger.Printf("brc pulse high: %v", err)
+	}
+}
+
+func exportGPIO(pin int) error {
+	err := os.WriteFile("/sys/class/gpio/export", []byte(strconv.Itoa(pin)), 0o644)
+	if err != nil && !os.IsExist(err) {
+		return err
+	}
+	return nil
+}
+
+func unexportGPIO(pin int) error {
+	err := os.WriteFile("/sys/class/gpio/unexport", []byte(strconv.Itoa(pin)), 0o644)
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	return nil
+}
+
+func writeGPIO(pin int, field string, data []byte) error {
+	path := filepath.Join("/sys/class/gpio", fmt.Sprintf("gpio%d", pin), field)
+	return os.WriteFile(path, data, 0o644)
+}