1 files changed, 146 insertions, 0 deletions
diff --git a/src/machine/machine_rp2_adc.go b/src/machine/machine_rp2_adc.go
new file mode 100644
index 000000000..13504d719
--- /dev/null
+++ b/src/machine/machine_rp2_adc.go
@@ -0,0 +1,146 @@
+//go:build rp2040 || rp2350
+
+package machine
+
+import (
+	"device/rp"
+	"errors"
+	"sync"
+)
+
+// ADCChannel is the ADC peripheral mux channel. 0-4.
+type ADCChannel uint8
+
+// ADC channels. Only ADC_TEMP_SENSOR is public. The other channels are accessed via Machine.ADC objects
+const (
+	adc0_CH ADCChannel = iota
+	adc1_CH
+	adc2_CH
+	adc3_CH       // Note: GPIO29 not broken out on pico board
+	adcTempSensor // Internal temperature sensor channel
+)
+
+// Used to serialise ADC sampling
+var adcLock sync.Mutex
+
+// ADC peripheral reference voltage (mV)
+var adcAref uint32
+
+// InitADC resets the ADC peripheral.
+func InitADC() {
+	rp.RESETS.RESET.SetBits(rp.RESETS_RESET_ADC)
+	rp.RESETS.RESET.ClearBits(rp.RESETS_RESET_ADC)
+	for !rp.RESETS.RESET_DONE.HasBits(rp.RESETS_RESET_ADC) {
+	}
+	// enable ADC
+	rp.ADC.CS.Set(rp.ADC_CS_EN)
+	adcAref = 3300
+	waitForReady()
+}
+
+// Configure sets the ADC pin to analog input mode.
+func (a ADC) Configure(config ADCConfig) error {
+	c, err := a.GetADCChannel()
+	if err != nil {
+		return err
+	}
+	return c.Configure(config)
+}
+
+// Get returns a one-shot ADC sample reading.
+func (a ADC) Get() uint16 {
+	if c, err := a.GetADCChannel(); err == nil {
+		return c.getOnce()
+	}
+	// Not an ADC pin!
+	return 0
+}
+
+// GetADCChannel returns the channel associated with the ADC pin.
+func (a ADC) GetADCChannel() (c ADCChannel, err error) {
+	err = nil
+	switch a.Pin {
+	case ADC0:
+		c = adc0_CH
+	case ADC1:
+		c = adc1_CH
+	case ADC2:
+		c = adc2_CH
+	case ADC3:
+		c = adc3_CH
+	default:
+		err = errors.New("no ADC channel for pin value")
+	}
+	return c, err
+}
+
+// Configure sets the channel's associated pin to analog input mode.
+// The powered on temperature sensor increases ADC_AVDD current by approximately 40 μA.
+func (c ADCChannel) Configure(config ADCConfig) error {
+	if config.Reference != 0 {
+		adcAref = config.Reference
+	}
+	p, err := c.Pin()
+	if err != nil {
+		return err
+	}
+	p.Configure(PinConfig{Mode: PinAnalog})
+	return nil
+}
+
+// getOnce returns a one-shot ADC sample reading from an ADC channel.
+func (c ADCChannel) getOnce() uint16 {
+	// Make it safe to sample multiple ADC channels in separate go routines.
+	adcLock.Lock()
+	rp.ADC.CS.ReplaceBits(uint32(c), 0b111, rp.ADC_CS_AINSEL_Pos)
+	rp.ADC.CS.SetBits(rp.ADC_CS_START_ONCE)
+
+	waitForReady()
+	adcLock.Unlock()
+
+	// rp2040 is a 12-bit ADC, scale raw reading to 16-bits.
+	return uint16(rp.ADC.RESULT.Get()) << 4
+}
+
+// getVoltage does a one-shot sample and returns a millivolts reading.
+// Integer portion is stored in the high 16 bits and fractional in the low 16 bits.
+func (c ADCChannel) getVoltage() uint32 {
+	return (adcAref << 16) / (1 << 12) * uint32(c.getOnce()>>4)
+}
+
+// ReadTemperature does a one-shot sample of the internal temperature sensor and returns a milli-celsius reading.
+func ReadTemperature() (millicelsius int32) {
+	if rp.ADC.CS.Get()&rp.ADC_CS_EN == 0 {
+		InitADC()
+	}
+
+	// Enable temperature sensor bias source
+	rp.ADC.CS.SetBits(rp.ADC_CS_TS_EN)
+
+	// T = 27 - (ADC_voltage - 0.706)/0.001721
+	return (27000<<16 - (int32(adcTempSensor.getVoltage())-706<<16)*581) >> 16
+}
+
+// waitForReady spins waiting for the ADC peripheral to become ready.
+func waitForReady() {
+	for !rp.ADC.CS.HasBits(rp.ADC_CS_READY) {
+	}
+}
+
+// The Pin method returns the GPIO Pin associated with the ADC mux channel, if it has one.
+func (c ADCChannel) Pin() (p Pin, err error) {
+	err = nil
+	switch c {
+	case adc0_CH:
+		p = ADC0
+	case adc1_CH:
+		p = ADC1
+	case adc2_CH:
+		p = ADC2
+	case adc3_CH:
+		p = ADC3
+	default:
+		err = errors.New("no associated pin for channel")
+	}
+	return p, err
+}