131 lines
3.9 KiB
C
131 lines
3.9 KiB
C
#include "py/obj.h"
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#include "py/runtime.h"
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#include "shared-bindings/microcontroller/Pin.h"
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#include "samd/pins.h"
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#include "sam.h"
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STATIC mp_obj_t _bhb_read_adc(void);
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STATIC mp_obj_t _bhb_init_adc(void) {
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claim_pin(&pin_PB08);
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common_hal_never_reset_pin(&pin_PB08);
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/* Enable the APB clock for the ADC. */
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PM->APBCMASK.reg |= PM_APBCMASK_ADC;
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/* Enable GCLK0 for the ADC */
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GCLK->CLKCTRL.reg = GCLK_CLKCTRL_CLKEN |
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GCLK_CLKCTRL_GEN_GCLK0 |
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GCLK_CLKCTRL_ID_ADC;
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/* Wait for bus synchronization. */
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while (GCLK->STATUS.bit.SYNCBUSY) {
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}
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;
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uint32_t bias = (*((uint32_t *)ADC_FUSES_BIASCAL_ADDR) & ADC_FUSES_BIASCAL_Msk) >> ADC_FUSES_BIASCAL_Pos;
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uint32_t linearity = (*((uint32_t *)ADC_FUSES_LINEARITY_0_ADDR) & ADC_FUSES_LINEARITY_0_Msk) >> ADC_FUSES_LINEARITY_0_Pos;
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linearity |= ((*((uint32_t *)ADC_FUSES_LINEARITY_1_ADDR) & ADC_FUSES_LINEARITY_1_Msk) >> ADC_FUSES_LINEARITY_1_Pos) << 5;
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/* Wait for bus synchronization. */
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while (ADC->STATUS.bit.SYNCBUSY) {
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}
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;
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/* Write the calibration data. */
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ADC->CALIB.reg = ADC_CALIB_BIAS_CAL(bias) | ADC_CALIB_LINEARITY_CAL(linearity);
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/* Use the internal VCC reference. This is 1/2 of what's on VCCA.
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since VCCA is 3.3v, this is 1.65v.
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*/
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ADC->REFCTRL.reg = ADC_REFCTRL_REFSEL_INTVCC1;
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/* Capture 64 samples. */
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ADC->AVGCTRL.reg = ADC_AVGCTRL_SAMPLENUM_64 | ADC_AVGCTRL_ADJRES(4);
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/* Set the clock prescaler to 32, which is the same as the CircuitPython default.
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Set the resolution to 16 for averaging
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*/
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ADC->CTRLB.reg = ADC_CTRLB_PRESCALER_DIV32 |
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ADC_CTRLB_RESSEL_16BIT;
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/* Configure the input parameters.
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- GAIN_DIV2 means that the input voltage is halved. This is important
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because the voltage reference is 1/2 of VCCA. So if you want to
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measure 0-3.3v, you need to halve the input as well.
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- MUXNEG_GND means that the ADC should compare the input value to GND.
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- MUXPOS_PIN3 means that the ADC should read from AIN2, or PB08.
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*/
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ADC->INPUTCTRL.reg = ADC_INPUTCTRL_GAIN_DIV2 |
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ADC_INPUTCTRL_MUXNEG_GND |
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ADC_INPUTCTRL_MUXPOS_PIN2;
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/* Set PB08 as an input pin. */
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PORT->Group[1].DIRCLR.reg = PORT_PB08;
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/* Enable the peripheral multiplexer for PB08. */
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PORT->Group[1].PINCFG[8].reg |= PORT_PINCFG_PMUXEN;
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/* Set PB08 to function B which is analog input. */
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PORT->Group[1].PMUX[4].reg |= PORT_PMUX_PMUXE_B;
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/* Wait for bus synchronization. */
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while (ADC->STATUS.bit.SYNCBUSY) {
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}
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;
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/* Enable the ADC. */
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ADC->CTRLA.bit.ENABLE = true;
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/* Make one read and throw it away, as per the datasheet. */
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_bhb_read_adc();
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return mp_const_none;
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}
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STATIC mp_obj_t _bhb_read_adc(void) {
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/* Wait for bus synchronization. */
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while (ADC->STATUS.bit.SYNCBUSY) {
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}
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;
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/* Start the ADC using a software trigger. */
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ADC->SWTRIG.bit.START = true;
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/* Wait for the result ready flag to be set. */
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while (ADC->INTFLAG.bit.RESRDY == 0) {
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;
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}
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/* Clear the flag. */
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ADC->INTFLAG.reg = ADC_INTFLAG_RESRDY;
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/* Read the value. */
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uint32_t result = ADC->RESULT.reg;
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return MP_OBJ_NEW_SMALL_INT(result);
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}
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STATIC MP_DEFINE_CONST_FUN_OBJ_0(_bhb_init_adc_obj, _bhb_init_adc);
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STATIC MP_DEFINE_CONST_FUN_OBJ_0(_bhb_read_adc_obj, _bhb_read_adc);
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STATIC const mp_rom_map_elem_t _bhb_module_globals_table[] = {
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{ MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR__bhb) },
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{ MP_ROM_QSTR(MP_QSTR_init_adc), MP_ROM_PTR(&_bhb_init_adc_obj) },
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{ MP_ROM_QSTR(MP_QSTR_read_adc), MP_ROM_PTR(&_bhb_read_adc_obj) },
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};
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STATIC MP_DEFINE_CONST_DICT(_bhb_module_globals, _bhb_module_globals_table);
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const mp_obj_module_t _bhb_user_cmodule = {
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.base = { &mp_type_module },
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.globals = (mp_obj_dict_t *)&_bhb_module_globals,
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};
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MP_REGISTER_MODULE(MP_QSTR__bhb, _bhb_user_cmodule, MODULE_BHB_ENABLED);
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