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//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
}
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