add PCA9685 driver

examples/pca9685/main.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/pca9685"
+)
+
+func main() {
+	const (
+		// Default address on most breakout boards.
+		pcaAddr = 0x40
+	)
+	err := machine.I2C0.Configure(machine.I2CConfig{})
+	if err != nil {
+		panic(err.Error())
+	}
+	d := pca9685.New(machine.I2C0, 0x40)
+	err = d.IsConnected()
+	if err != nil {
+		panic(err.Error())
+	}
+	err = d.Configure(pca9685.PWMConfig{Period: 1e9 / 200}) // 200Hz PWM
+	if err != nil {
+		panic(err.Error())
+	}
+
+	var value uint32
+	step := d.Top() / 5
+	for {
+		for value = 0; value <= d.Top(); value += step {
+			d.SetAll(value)
+			dc := 100 * value / d.Top()
+			println("set dc @", dc, "%")
+			time.Sleep(800 * time.Millisecond)
+		}
+	}
+}
+
+// ScanI2CDev finds I2C devices on the bus and rreturns them inside
+// a slice. If slice is nil then no devices were found.
+func ScanI2CDev(bus machine.I2C) (addrs []uint8) {
+	var addr, count uint8
+	var err error
+	w := []byte{1}
+	// Count devices in first scan
+	for addr = 1; addr < 127; addr++ {
+		err = bus.Tx(uint16(addr), w, nil)
+		if err == nil {
+			count++
+		}
+	}
+	if count == 0 {
+		return nil
+	}
+	// Allocate slice and populate slice with addresses
+	addrs = make([]uint8, count)
+	count = 0
+	for addr = 1; addr < 127; addr++ {
+		err = bus.Tx(uint16(addr), w, nil)
+		if err == nil && count < uint8(len(addrs)) {
+			addrs[count] = addr
+			count++
+		}
+	}
+	return addrs
+}