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machine/esp32: add ADC driver (#5595)
* machine/esp32: add ADC driver Implements ADC1 on the Xtensa ESP32: InitADC, Configure and Get for GPIO36, GPIO37, GPIO38, GPIO39, GPIO32, GPIO33, GPIO34 and GPIO35 (channels 0-7). The ADC pins are not contiguous on this chip, so the pin to channel mapping is a lookup rather than arithmetic as on the ESP32-S3. Conversions are driven by the RTC controller under software control, and Get returns the 12-bit sample scaled to 0..65520 to match the other ESP ADC drivers. The analog pads are spread over three unrelated RTC_IO registers (SENSOR_PADS, XTAL_32K_PAD and ADC_PAD), so pad setup is kept local to this file rather than adding a PinAnalog mode to machine_esp32.go. That keeps the change to a single file. Values are raw and uncalibrated. Unlike the ESP32-C3, S3 and C6 drivers there is no eFuse or self-calibration step; accurate voltage mapping should be done with a two-point calibration in user code. ADC2 is not implemented. On the ESP32 it is shared with the Wi-Fi radio and cannot be used reliably while the radio is active. Tested on an ESP32 Coreboard V2 with a photoresistor divider on GPIO36. Readings swept 5056..59824 over the light range, all eight channels returned independent values, and an invalid pin returned an error from Configure and 0 from Get. Signed-off-by: zombieleet <osikwemhev@gmail.com> * fix: use package level err definiition and return (uint32, bool) from adcRTCGPIO --------- Signed-off-by: zombieleet <osikwemhev@gmail.com>
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@@ -989,6 +989,8 @@ endif
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ifneq ($(XTENSA), 0)
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$(TINYGO) build -size short -o test.bin -target=esp32-generic examples/machinetest
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@$(MD5SUM) test.bin
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$(TINYGO) build -size short -o test.bin -target=esp32-coreboard-v2 examples/adc
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@$(MD5SUM) test.bin
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$(TINYGO) build -size short -o test.bin -target=esp32c3-generic examples/machinetest
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@$(MD5SUM) test.bin
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$(TINYGO) build -size short -o test.bin -target=esp32s3-generic examples/machinetest
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@@ -0,0 +1,237 @@
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//go:build esp32
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// ESP32 (Xtensa): SAR ADC1, 12-bit hardware; Get() returns 0..65520 (scaled
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// from 12-bit).
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//
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// Pin mapping is not contiguous, so a lookup is used instead of arithmetic:
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// ADC1 channels 0..7 are GPIO36, 37, 38, 39, 32, 33, 34, 35.
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//
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// ADC1 is driven by the RTC controller under software control: SAR1_DIG_FORCE
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// selects the RTC controller, MEAS1_START_FORCE and SAR1_EN_PAD_FORCE hand
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// channel selection and triggering to software, then MEAS1_START_SAR 0->1
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// starts a conversion and MEAS1_DATA_SAR holds the 12-bit result.
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//
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// Get() returns raw, uncalibrated values. Unlike the ESP32-C3/S3/C6 drivers
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// there is no eFuse or self-calibration step here; accurate voltage mapping
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// should be done with a two-point calibration in user code.
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//
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// ADC2 is deliberately not implemented. On the ESP32 it is shared with the
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// Wi-Fi radio and cannot be used reliably while the radio is active.
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package machine
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import (
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"device/esp"
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"errors"
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)
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const (
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// 11 dB, the widest input range the SAR offers (IDF ADC_ATTEN_DB_12).
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adcAtten11dB = 3
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// SAR1_BIT_WIDTH / SAR1_SAMPLE_BIT value selecting 12-bit conversions.
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adcWidth12Bit = 3
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// Divider for the ADC's own clock, matching the IDF default for ADC1.
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adcClkDiv = 2
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)
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var (
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ErrInvalidADCPin = errors.New("invalid ADC pin for ESP32")
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)
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// InitADC powers up SAR ADC1 and puts it under software control.
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func InitADC() {
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// The SAR front end is shared with the hall sensor and an internal
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// amplifier. Both must be off or channel readings pick up their bias.
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esp.SENS.SetSAR_TOUCH_CTRL1_XPD_HALL_FORCE(1)
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esp.SENS.SetSAR_TOUCH_CTRL1_HALL_PHASE_FORCE(1)
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esp.RTC_IO.SetHALL_SENS_XPD_HALL(0)
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esp.SENS.SetSAR_MEAS_WAIT2_FORCE_XPD_AMP(2) // 2 = force power down
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esp.SENS.SetSAR_MEAS_CTRL_AMP_RST_FB_FSM(0)
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esp.SENS.SetSAR_MEAS_CTRL_AMP_SHORT_REF_FSM(0)
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esp.SENS.SetSAR_MEAS_CTRL_AMP_SHORT_REF_GND_FSM(0)
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esp.SENS.SetSAR_MEAS_WAIT1_SAR_AMP_WAIT1(1)
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esp.SENS.SetSAR_MEAS_WAIT1_SAR_AMP_WAIT2(1)
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esp.SENS.SetSAR_MEAS_WAIT2_SAR_AMP_WAIT3(1)
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// Drive ADC1 from the RTC controller rather than the digital/DMA path.
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// The RTC domain is always clocked, so no clock gate has to be opened.
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esp.SENS.SetSAR_READ_CTRL_SAR1_DIG_FORCE(0)
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esp.SENS.SetSAR_MEAS_START1_MEAS1_START_FORCE(1)
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esp.SENS.SetSAR_MEAS_START1_SAR1_EN_PAD_FORCE(1)
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esp.SENS.SetSAR_MEAS_WAIT2_FORCE_XPD_SAR(3) // 3 = force power up
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esp.SENS.SetSAR_START_FORCE_SAR1_BIT_WIDTH(adcWidth12Bit)
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esp.SENS.SetSAR_READ_CTRL_SAR1_SAMPLE_BIT(adcWidth12Bit)
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esp.SENS.SetSAR_READ_CTRL_SAR1_CLK_DIV(adcClkDiv)
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// ADC1 returns the sample inverted; this flips it so readings rise with
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// the input voltage.
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esp.SENS.SetSAR_READ_CTRL_SAR1_DATA_INV(1)
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}
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// Configure routes the pin to the SAR ADC and sets its attenuation. It returns
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// an error if the pin has no ADC1 channel. ADCConfig is accepted for API
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// compatibility but its fields are not used; attenuation is fixed at 11 dB.
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func (a ADC) Configure(config ADCConfig) error {
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ch, ok := adc1Channel(a.Pin)
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if !ok {
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return ErrInvalidADCPin
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}
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configureADCPad(a.Pin)
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setSensAtten1(ch, adcAtten11dB)
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return nil
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}
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// Get runs a single conversion and returns the result scaled from the 12-bit
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// hardware value to the full 16-bit range, so values run 0..65520. It returns
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// 0 if the pin has no ADC1 channel.
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func (a ADC) Get() uint16 {
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ch, ok := adc1Channel(a.Pin)
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if !ok {
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return 0
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}
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// SAR1_EN_PAD is a one-hot mask, not a channel index.
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esp.SENS.SetSAR_MEAS_START1_SAR1_EN_PAD(1 << ch)
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// The touch and ULP state machines share the SAR over an internal bus;
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// wait for a conversion already in flight to finish.
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for esp.SENS.GetSAR_SLAVE_ADDR1_MEAS_STATUS() != 0 {
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}
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// The conversion is triggered by the 0->1 edge, so the bit has to be
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// taken low first in case a previous call left it high.
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esp.SENS.SetSAR_MEAS_START1_MEAS1_START_SAR(0)
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esp.SENS.SetSAR_MEAS_START1_MEAS1_START_SAR(1)
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for esp.SENS.GetSAR_MEAS_START1_MEAS1_DONE_SAR() == 0 {
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}
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raw := esp.SENS.GetSAR_MEAS_START1_MEAS1_DATA_SAR()
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return uint16(raw&0xfff) << 4
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}
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// adc1Channel maps a pin to its ADC1 channel. The ESP32's ADC pins are not
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// contiguous, so this cannot be computed from the pin number.
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func adc1Channel(p Pin) (uint32, bool) {
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switch p {
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case GPIO36:
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return 0, true
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case GPIO37:
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return 1, true
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case GPIO38:
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return 2, true
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case GPIO39:
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return 3, true
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case GPIO32:
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return 4, true
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case GPIO33:
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return 5, true
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case GPIO34:
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return 6, true
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case GPIO35:
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return 7, true
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}
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return 0, false
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}
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// configureADCPad hands the pad to the RTC domain and takes it out of digital
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// mode, so the SAR sees the analog level.
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//
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// The pads are spread over three different RTC_IO registers with unrelated
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// field names, so each group is handled separately. GPIO34-39 have no internal
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// pull resistors, which is why only the GPIO32/33 group disables them.
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func configureADCPad(p Pin) {
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switch p {
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case GPIO36:
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esp.RTC_IO.SetSENSOR_PADS_SENSE1_MUX_SEL(1)
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esp.RTC_IO.SetSENSOR_PADS_SENSE1_FUN_SEL(0)
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esp.RTC_IO.SetSENSOR_PADS_SENSE1_FUN_IE(0)
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case GPIO37:
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esp.RTC_IO.SetSENSOR_PADS_SENSE2_MUX_SEL(1)
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esp.RTC_IO.SetSENSOR_PADS_SENSE2_FUN_SEL(0)
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esp.RTC_IO.SetSENSOR_PADS_SENSE2_FUN_IE(0)
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case GPIO38:
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esp.RTC_IO.SetSENSOR_PADS_SENSE3_MUX_SEL(1)
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esp.RTC_IO.SetSENSOR_PADS_SENSE3_FUN_SEL(0)
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esp.RTC_IO.SetSENSOR_PADS_SENSE3_FUN_IE(0)
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case GPIO39:
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esp.RTC_IO.SetSENSOR_PADS_SENSE4_MUX_SEL(1)
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esp.RTC_IO.SetSENSOR_PADS_SENSE4_FUN_SEL(0)
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esp.RTC_IO.SetSENSOR_PADS_SENSE4_FUN_IE(0)
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case GPIO32:
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esp.RTC_IO.SetXTAL_32K_PAD_X32P_MUX_SEL(1)
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esp.RTC_IO.SetXTAL_32K_PAD_X32P_FUN_SEL(0)
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esp.RTC_IO.SetXTAL_32K_PAD_X32P_FUN_IE(0)
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esp.RTC_IO.SetXTAL_32K_PAD_X32P_RUE(0)
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esp.RTC_IO.SetXTAL_32K_PAD_X32P_RDE(0)
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case GPIO33:
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esp.RTC_IO.SetXTAL_32K_PAD_X32N_MUX_SEL(1)
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esp.RTC_IO.SetXTAL_32K_PAD_X32N_FUN_SEL(0)
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esp.RTC_IO.SetXTAL_32K_PAD_X32N_FUN_IE(0)
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esp.RTC_IO.SetXTAL_32K_PAD_X32N_RUE(0)
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esp.RTC_IO.SetXTAL_32K_PAD_X32N_RDE(0)
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case GPIO34:
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// ADC_PAD_ADC1 is a pad name: it is GPIO34, ADC1 channel 6.
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esp.RTC_IO.SetADC_PAD_ADC1_MUX_SEL(1)
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esp.RTC_IO.SetADC_PAD_ADC1_FUN_SEL(0)
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esp.RTC_IO.SetADC_PAD_ADC1_FUN_IE(0)
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case GPIO35:
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// ADC_PAD_ADC2 is a pad name: it is GPIO35, ADC1 channel 7.
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esp.RTC_IO.SetADC_PAD_ADC2_MUX_SEL(1)
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esp.RTC_IO.SetADC_PAD_ADC2_FUN_SEL(0)
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esp.RTC_IO.SetADC_PAD_ADC2_FUN_IE(0)
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default:
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return
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}
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ch, ok := adcRTCGPIO(p)
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if !ok {
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return
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}
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// Take the RTC output driver off the pad so nothing fights the input.
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esp.RTC_IO.SetENABLE_W1TC(1 << ch)
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}
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// adcRTCGPIO maps a pin to its index within the RTC GPIO block, which is
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// numbered independently of the main GPIO matrix.
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func adcRTCGPIO(p Pin) (uint32, bool) {
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switch p {
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case GPIO36:
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return 0, true
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case GPIO37:
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return 1, true
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case GPIO38:
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return 2, true
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case GPIO39:
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return 3, true
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case GPIO34:
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return 4, true
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case GPIO35:
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return 5, true
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case GPIO33:
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return 8, true
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case GPIO32:
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return 9, true
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}
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return 0, false
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}
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// setSensAtten1 sets the 2-bit attenuation field for one ADC1 channel. The
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// generated code exposes SAR_ATTEN1 only as a whole register, so the
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// read-modify-write is done here.
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func setSensAtten1(ch, atten uint32) {
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v := esp.SENS.GetSAR_ATTEN1()
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v &^= 3 << (ch * 2)
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v |= (atten & 3) << (ch * 2)
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esp.SENS.SetSAR_ATTEN1(v)
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}
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