Adding driver for rotary encoder support

encoders/quadrature_device.go

@@ -0,0 +1,34 @@
+package encoders
+
+type QuadratureDevice struct {
+	cfg  QuadratureConfig
+	impl quadratureImpl
+}
+
+type QuadratureConfig struct {
+	Precision int
+}
+
+type quadratureImpl interface {
+	configure(cfg QuadratureConfig) error
+	readValue() int
+	writeValue(int)
+}
+
+func (enc *QuadratureDevice) Configure(cfg QuadratureConfig) error {
+	if cfg.Precision < 1 {
+		cfg.Precision = 4
+	}
+	enc.cfg = cfg
+	return enc.impl.configure(cfg)
+}
+
+// Position returns the stored int value for the encoder
+func (enc *QuadratureDevice) Position() int {
+	return enc.impl.readValue() / enc.cfg.Precision
+}
+
+// SetPosition overwrites the currently stored value with the specified int value
+func (enc *QuadratureDevice) SetPosition(v int) {
+	enc.impl.writeValue(v * enc.cfg.Precision)
+}

encoders/quadrature_interrupt.go

@@ -0,0 +1,69 @@
+//go:build tinygo && (rp2040 || stm32 || k210 || esp32c3 || nrf || (avr && (atmega328p || atmega328pb)))
+
+// Implementation based on:
+// https://gist.github.com/aykevl/3fc1683ed77bb0a9c07559dfe857304a
+
+// Note: build constraints in this file list targets that define machine.PinToggle.
+// If this is supported for additional targets in the future, they can be added above.
+
+package encoders
+
+import (
+	"machine"
+	"runtime/volatile"
+)
+
+var (
+	states = []int8{0, -1, 1, 0, 1, 0, 0, -1, -1, 0, 0, 1, 0, 1, -1, 0}
+)
+
+// NewQuadratureViaInterrupt returns a rotary encoder device that uses GPIO
+// interrupts and a lookup table to keep track of quadrature state changes.
+//
+// This constructur is only available for TinyGo targets for which machine.PinToggle
+// is defined as a valid interrupt type.
+func NewQuadratureViaInterrupt(pinA, pinB machine.Pin) *QuadratureDevice {
+	return &QuadratureDevice{impl: &quadInterruptImpl{pinA: pinA, pinB: pinB, oldAB: 0b00000011}}
+}
+
+type quadInterruptImpl struct {
+	pinA machine.Pin
+	pinB machine.Pin
+
+	// precision int
+
+	oldAB int
+	value volatile.Register32
+}
+
+func (enc *quadInterruptImpl) configure(cfg QuadratureConfig) error {
+	enc.pinA.Configure(machine.PinConfig{Mode: machine.PinInputPullup})
+	enc.pinA.SetInterrupt(machine.PinToggle, enc.interrupt)
+
+	enc.pinB.Configure(machine.PinConfig{Mode: machine.PinInputPullup})
+	enc.pinB.SetInterrupt(machine.PinToggle, enc.interrupt)
+
+	return nil
+}
+
+func (enc *quadInterruptImpl) interrupt(pin machine.Pin) {
+	aHigh, bHigh := enc.pinA.Get(), enc.pinB.Get()
+	enc.oldAB <<= 2
+	if aHigh {
+		enc.oldAB |= 1 << 1
+	}
+	if bHigh {
+		enc.oldAB |= 1
+	}
+	enc.writeValue(enc.readValue() + int(states[enc.oldAB&0x0f]))
+}
+
+// readValue gets the value using volatile operations and returns it as an int
+func (enc *quadInterruptImpl) readValue() int {
+	return int(enc.value.Get())
+}
+
+// writeValue set the value to the specified int using volatile operations
+func (enc *quadInterruptImpl) writeValue(v int) {
+	enc.value.Set(uint32(v))
+}