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Merged
tannewt merged 1 commit into from
Oct 15, 2017
Merged

Reinit ADC completely on each call to AnalogIn.value. #327

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76 changes: 21 additions & 55 deletions atmel-samd/common-hal/analogio/AnalogIn.c
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Original file line number Diff line number Diff line change
Expand Up @@ -38,13 +38,6 @@
#include "asf/sam0/drivers/adc/adc.h"
#include "samd21_pins.h"

// Number of active ADC channels.
volatile uint8_t active_channel_count;

// Shared between all the instances. Allocated only when needed.
struct adc_module *adc_instance = NULL;
struct adc_config *config_adc = NULL;

void common_hal_analogio_analogin_construct(analogio_analogin_obj_t* self,
const mcu_pin_obj_t *pin) {
if (!pin->has_adc) {
Expand All @@ -54,27 +47,6 @@ void common_hal_analogio_analogin_construct(analogio_analogin_obj_t* self,
claim_pin(pin);

self->pin = pin;

if (adc_instance == NULL) {
// Allocate strucs on the heap so we only use the memory when we
// need it.
adc_instance = gc_alloc(sizeof(struct adc_module), false);
config_adc = gc_alloc(sizeof(struct adc_config), false);

adc_get_config_defaults(config_adc);

config_adc->reference = ADC_REFERENCE_INTVCC1;
config_adc->gain_factor = ADC_GAIN_FACTOR_DIV2;
config_adc->positive_input = self->pin->adc_input;
config_adc->resolution = ADC_RESOLUTION_16BIT;
config_adc->clock_prescaler = ADC_CLOCK_PRESCALER_DIV128;

adc_init(adc_instance, ADC, config_adc);
}

self->adc_instance = adc_instance;
self->config_adc = config_adc;
active_channel_count++;
}

bool common_hal_analogio_analogin_deinited(analogio_analogin_obj_t *self) {
Expand All @@ -85,36 +57,30 @@ void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
if (common_hal_analogio_analogin_deinited(self)) {
return;
}
active_channel_count--;
if (active_channel_count == 0) {
adc_reset(adc_instance);
gc_free(adc_instance);
gc_free(config_adc);
// Set our references to NULL so the GC doesn't mistakenly see the
// pointers in memory.
adc_instance = NULL;
config_adc = NULL;
}
reset_pin(self->pin->pin);
self->pin = mp_const_none;
}

void analogin_reset() {
if (adc_instance != NULL) {
adc_reset(adc_instance);
adc_instance = NULL;
}
active_channel_count = 0;
}

uint16_t common_hal_analogio_analogin_get_value(analogio_analogin_obj_t *self) {
// Something else might have used the ADC in a different way,
// so we have to completely re-initialize it.
// ADC must have been disabled before adc_init() is called.
adc_init(adc_instance, ADC, config_adc);
config_adc->positive_input = self->pin->adc_input;
// so we completely re-initialize it.

adc_enable(adc_instance);
struct adc_config config_adc;
adc_get_config_defaults(&config_adc);

config_adc.reference = ADC_REFERENCE_INTVCC1;
config_adc.gain_factor = ADC_GAIN_FACTOR_DIV2;
config_adc.positive_input = self->pin->adc_input;
config_adc.resolution = ADC_RESOLUTION_16BIT;
config_adc.clock_prescaler = ADC_CLOCK_PRESCALER_DIV128;

struct adc_module adc_instance;
// ADC must have been disabled before adc_init() is called.
adc_init(&adc_instance, ADC, &config_adc);
adc_enable(&adc_instance);

// Read twice and discard first result, as recommended in section 14 of
// http://www.atmel.com/images/Atmel-42645-ADC-Configurations-with-Examples_ApplicationNote_AT11481.pdf
Expand All @@ -125,23 +91,23 @@ uint16_t common_hal_analogio_analogin_get_value(analogio_analogin_obj_t *self) {
uint16_t data;
enum status_code status;

adc_start_conversion(adc_instance);
adc_start_conversion(&adc_instance);
do {
status = adc_read(adc_instance, &data);
status = adc_read(&adc_instance, &data);
} while (status == STATUS_BUSY);
if (status == STATUS_ERR_OVERFLOW) {
// TODO(tannewt): Throw an error.
mp_raise_RuntimeError("ADC result overwritten before reading");
}

adc_start_conversion(adc_instance);
adc_start_conversion(&adc_instance);
do {
status = adc_read(adc_instance, &data);
status = adc_read(&adc_instance, &data);
} while (status == STATUS_BUSY);
if (status == STATUS_ERR_OVERFLOW) {
// TODO(tannewt): Throw an error.
mp_raise_RuntimeError("ADC result overwritten before reading");
}

adc_disable(adc_instance);
adc_disable(&adc_instance);
return data;
}

Expand Down
2 changes: 0 additions & 2 deletions atmel-samd/common-hal/analogio/AnalogIn.h
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Original file line number Diff line number Diff line change
Expand Up @@ -41,8 +41,6 @@
typedef struct {
mp_obj_base_t base;
const mcu_pin_obj_t * pin;
struct adc_module * adc_instance;
struct adc_config * config_adc;
} analogio_analogin_obj_t;

void analogin_reset(void);
Expand Down
1 change: 1 addition & 0 deletions atmel-samd/main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -203,6 +203,7 @@ void reset_samd21(void) {
analogin_reset();


// TODO: move this to analogout_reset()
// Wait for the DAC to sync then reset.
while (DAC->STATUS.reg & DAC_STATUS_SYNCBUSY) {}
DAC->CTRLA.reg |= DAC_CTRLA_SWRST;
Expand Down