Is ADC driver implemented for SAMD21G18A?

[IchiroKuroki]

The code does not compile if I use the adc.h interface with arduino-nano-33-iot.

#include "periph/adc.h"
adc_init(ADC_LINE(1));

make flash BOARD=arduino-nano-33-iot

undefined reference to `adc_init'
collect2: error: ld returned 1 exit status

If I add in the Makefile:

FEATURES_REQUIRED += periph_adc

then: There are unsatisfied feature requirements: periph_adc

[jeandudey]

Hi @IchiroKuroki , could you try to add FEATURES_PROVIDED += periph_adc to RIOT/boards/arduino-nano-33-iot and select HAS_PERIPH_ADC to RIOT/boards/arduino-nano-33-iot and try recompiling and verifying that the ADC works?

[IchiroKuroki]

Hi @jeandudey. After following your advice, I got new errors:

/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c:90:9: error: 'ADC_REF_DEFAULT' undeclared (first use in this function)
90 | if (ADC_REF_DEFAULT == ADC_REFCTRL_REFSEL_INT1V) {
| ^~~~~~~~~~~~~~~
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c:90:9: note: each undeclared identifier is reported only once for each function it appears in
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c: In function '_setup_clock':
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c:113:26: error: 'ADC_PRESCALER' undeclared (first use in this function)
113 | ADC_DEV->CTRLB.reg = ADC_PRESCALER;
| ^~~~~~~~~~~~~
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c: In function '_adc_configure':
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c:221:28: error: 'ADC_REF_DEFAULT' undeclared (first use in this function)
221 | ADC_DEV->REFCTRL.reg = ADC_REF_DEFAULT;
| ^~~~~~~~~~~~~~~
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c: In function 'adc_init':
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c:245:17: error: 'ADC_NUMOF' undeclared (first use in this function); did you mean 'DAC_NUMOF'?
245 | if (line >= ADC_NUMOF) {
| ^~~~~~~~~
| DAC_NUMOF
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c:251:15: error: 'adc_channels' undeclared (first use in this function)
251 | gpio_init(adc_channels[line].pin, GPIO_IN);
| ^~~~~~~~~~~~
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c: In function 'adc_sample':
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c:260:17: error: 'ADC_NUMOF' undeclared (first use in this function); did you mean 'DAC_NUMOF'?
260 | if (line >= ADC_NUMOF) {
| ^~~~~~~~~
| DAC_NUMOF
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c:274:30: error: 'adc_channels' undeclared (first use in this function)
274 | | adc_channels[line].muxpos
| ^~~~~~~~~~~~
/home/ichiro/Documents/projects/RIOT/cpu/sam0_common/periph/adc.c:275:30: error: 'ADC_NEG_INPUT' undeclared (first use in this function)
275 | | ADC_NEG_INPUT;

[jeandudey]

That's because there's no configuration for the ADC on the board, you could try to use a configuration and add it to the periph_conf.h file in that board, adapting it accordingly of course. Just for testing of course.

I will look into it to see if Arduino has some pins designated for the ADC on that board

[IchiroKuroki]

Arduino-zero has a close mcu - SAMD21G18(without A). I will try to compose the ADC and PWM configuration based on the configuration of this board.

[IchiroKuroki]

I started with PWM and this is the configuration I got:

#define PWM_0_EN 1
#define PWM_1_EN 1

#if PWM_0_EN
static const pwm_conf_chan_t pwm_chan0_config[] = {
// GPIO pin, MUX value, TCC channel
{ GPIO_PIN(PA, 4), GPIO_MUX_E, 0},
{ GPIO_PIN(PA, 5), GPIO_MUX_E, 1},
};
#endif
#if PWM_1_EN
static const pwm_conf_chan_t pwm_chan1_config[] = {
/* GPIO pin, MUX value, TCC channel */
{ GPIO_PIN(PA, 10), GPIO_MUX_E, 0 },
{ GPIO_PIN(PA, 11), GPIO_MUX_E, 1 },
};
#endif

static const pwm_conf_t pwm_config[] = {
#if PWM_0_EN
{TCC_CONFIG(TCC0), pwm_chan0_config, ARRAY_SIZE(pwm_chan0_config), SAM0_GCLK_MAIN},
#endif
#if PWM_1_EN
{TCC_CONFIG(TCC1), pwm_chan1_config, ARRAY_SIZE(pwm_chan1_config), SAM0_GCLK_MAIN},
#endif
}

I tested each pin with the stated PWM support using an oscilloscope. The following pins with declared PWM support are not present in this configuration:
PA02 - This pin is also used for DAC.
PB09 - This pin is also used for I2C.
PA16, PA19 - This pin is also used for SPI.
PA20, PA21, PB10, PB11 - PWM does not work on this pins(for my board).

I'll be working on ADC soon.

[IchiroKuroki]

For ADC, I got the following configuration:

#define ADC_PRESCALER ADC_CTRLB_PRESCALER_DIV512

#define ADC_NEG_INPUT ADC_INPUTCTRL_MUXNEG_GND
#define ADC_GAIN_FACTOR_DEFAULT ADC_INPUTCTRL_GAIN_1X
#define ADC_REF_DEFAULT ADC_REFCTRL_REFSEL_INT1V

static const adc_conf_chan_t adc_channels[] = {
/* port, pin, muxpos */
{GPIO_PIN(PA, 2), ADC_INPUTCTRL_MUXPOS_PIN0},
{GPIO_PIN(PB, 2), ADC_INPUTCTRL_MUXPOS_PIN10},
{GPIO_PIN(PA, 11), ADC_INPUTCTRL_MUXPOS_PIN19},
{GPIO_PIN(PA, 10), ADC_INPUTCTRL_MUXPOS_PIN18},
{GPIO_PIN(PB, 8), ADC_INPUTCTRL_MUXPOS_PIN2},
{GPIO_PIN(PB, 9), ADC_INPUTCTRL_MUXPOS_PIN3},
{GPIO_PIN(PA, 9), ADC_INPUTCTRL_MUXPOS_PIN17},
{GPIO_PIN(PB, 3), ADC_INPUTCTRL_MUXPOS_PIN11},
};

[benpicco]

If you have found a working configuration for arduino-nano-33-iot, feel free to open a PR.