mcp23017: new driver for MCP23017 (I2C port expander)

Author: rogpeppe

Makefile

@@ -83,6 +83,8 @@ smoke-test:
 	@md5sum ./build/test.hex
 	tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mag3110/main.go
 	@md5sum ./build/test.hex
+	tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp23017/main.go
+	@md5sum ./build/test.hex
 	tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp3008/main.go
 	@md5sum ./build/test.hex
 	tinygo build -size short -o ./build/test.hex -target=microbit ./examples/microbitmatrix/main.go

examples/mcp23017/main.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"machine"
+
+	"tinygo.org/x/drivers/mcp23017"
+)
+
+func main() {
+	err := machine.I2C0.Configure(machine.I2CConfig{
+		Frequency: machine.TWI_FREQ_400KHZ,
+	})
+	if err != nil {
+		panic(err)
+	}
+	dev, err := mcp23017.NewI2C(machine.I2C0, 0x20)
+	if err != nil {
+		panic(err)
+	}
+	// Configure pin 0 for input and all the others for output.
+	if err := dev.SetModes([]mcp23017.PinMode{
+		mcp23017.Input | mcp23017.Pullup,
+		mcp23017.Output,
+	}); err != nil {
+		panic(err)
+	}
+	input := dev.Pin(0)
+	outputMask := ^mcp23017.Pins(1 << 0) // All except pin 0
+	inputVal, err := input.Get()
+	if err != nil {
+		panic(err)
+	}
+	println("input value: ", inputVal)
+	// Set the values of all the output pins.
+	err = dev.SetPins(0b1011011_01101110, outputMask)
+	if err != nil {
+		panic(err)
+	}
+}