Merge pull request #3166 from theacodes/bhb-adc

Add _bhb user module for Big Honking Button

Author: tannewt

ports/atmel-samd/boards/winterbloom_big_honking_button/mpconfigboard.mk

@@ -31,3 +31,7 @@ CIRCUITPY_PS2IO = 0
 CIRCUITPY_USB_HID = 0
 CIRCUITPY_USB_MIDI = 0
 CIRCUITPY_RTC = 0
+
+# Enable board-specific modules
+USER_C_MODULES = boards/winterbloom_big_honking_button/usermods
+CFLAGS += -DMODULE_BHB_ENABLED=1

ports/atmel-samd/boards/winterbloom_big_honking_button/usermods/_bhb/bhb.c

@@ -0,0 +1,120 @@
+#include "py/obj.h"
+#include "py/runtime.h"
+#include "shared-bindings/microcontroller/Pin.h"
+#include "samd/pins.h"
+#include "sam.h"
+
+STATIC mp_obj_t _bhb_read_adc(void);
+
+STATIC mp_obj_t _bhb_init_adc(void) {
+    claim_pin(&pin_PB08);
+    common_hal_never_reset_pin(&pin_PB08);
+
+    /* Enable the APB clock for the ADC. */
+    PM->APBCMASK.reg |= PM_APBCMASK_ADC;
+
+    /* Enable GCLK0 for the ADC */
+    GCLK->CLKCTRL.reg = GCLK_CLKCTRL_CLKEN |
+                        GCLK_CLKCTRL_GEN_GCLK0 |
+                        GCLK_CLKCTRL_ID_ADC;
+
+    /* Wait for bus synchronization. */
+    while (GCLK->STATUS.bit.SYNCBUSY) {};
+
+    uint32_t bias = (*((uint32_t *) ADC_FUSES_BIASCAL_ADDR) & ADC_FUSES_BIASCAL_Msk) >> ADC_FUSES_BIASCAL_Pos;
+    uint32_t linearity = (*((uint32_t *) ADC_FUSES_LINEARITY_0_ADDR) & ADC_FUSES_LINEARITY_0_Msk) >> ADC_FUSES_LINEARITY_0_Pos;
+    linearity |= ((*((uint32_t *) ADC_FUSES_LINEARITY_1_ADDR) & ADC_FUSES_LINEARITY_1_Msk) >> ADC_FUSES_LINEARITY_1_Pos) << 5;
+
+    /* Wait for bus synchronization. */
+    while (ADC->STATUS.bit.SYNCBUSY) {};
+
+    /* Write the calibration data. */
+    ADC->CALIB.reg = ADC_CALIB_BIAS_CAL(bias) | ADC_CALIB_LINEARITY_CAL(linearity);
+
+    /* Use the internal VCC reference. This is 1/2 of what's on VCCA.
+       since VCCA is 3.3v, this is 1.65v.
+    */
+    ADC->REFCTRL.reg = ADC_REFCTRL_REFSEL_INTVCC1;
+
+    /* Capture 64 samples. */
+    ADC->AVGCTRL.reg = ADC_AVGCTRL_SAMPLENUM_64 | ADC_AVGCTRL_ADJRES(4);
+
+    /* Set the clock prescaler to 32, which is the same as the CircuitPython default.
+       Set the resolution to 16 for averaging
+    */
+    ADC->CTRLB.reg = ADC_CTRLB_PRESCALER_DIV32 |
+                     ADC_CTRLB_RESSEL_16BIT;
+
+    /* Configure the input parameters.
+
+    - GAIN_DIV2 means that the input voltage is halved. This is important
+      because the voltage reference is 1/2 of VCCA. So if you want to
+      measure 0-3.3v, you need to halve the input as well.
+
+    - MUXNEG_GND means that the ADC should compare the input value to GND.
+
+    - MUXPOS_PIN3 means that the ADC should read from AIN2, or PB08.
+    */
+    ADC->INPUTCTRL.reg = ADC_INPUTCTRL_GAIN_DIV2 |
+                         ADC_INPUTCTRL_MUXNEG_GND |
+                         ADC_INPUTCTRL_MUXPOS_PIN2;
+
+
+    /* Set PB08 as an input pin. */
+    PORT->Group[1].DIRCLR.reg = PORT_PB08;
+
+    /* Enable the peripheral multiplexer for PB08. */
+    PORT->Group[1].PINCFG[8].reg |= PORT_PINCFG_PMUXEN;
+
+    /* Set PB08 to function B which is analog input. */
+    PORT->Group[1].PMUX[4].reg |= PORT_PMUX_PMUXE_B;
+
+    /* Wait for bus synchronization. */
+    while (ADC->STATUS.bit.SYNCBUSY) {};
+
+    /* Enable the ADC. */
+    ADC->CTRLA.bit.ENABLE = true;
+
+    /* Make one read and throw it away, as per the datasheet. */
+    _bhb_read_adc();
+
+    return mp_const_none;
+}
+
+STATIC mp_obj_t _bhb_read_adc(void) {
+    /* Wait for bus synchronization. */
+    while (ADC->STATUS.bit.SYNCBUSY) {};
+
+    /* Start the ADC using a software trigger. */
+    ADC->SWTRIG.bit.START = true;
+
+    /* Wait for the result ready flag to be set. */
+    while (ADC->INTFLAG.bit.RESRDY == 0);
+
+    /* Clear the flag. */
+    ADC->INTFLAG.reg = ADC_INTFLAG_RESRDY;
+
+    /* Read the value. */
+    uint32_t result = ADC->RESULT.reg;
+
+    return MP_OBJ_NEW_SMALL_INT(result);
+}
+
+
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(_bhb_init_adc_obj, _bhb_init_adc);
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(_bhb_read_adc_obj, _bhb_read_adc);
+
+STATIC const mp_rom_map_elem_t _bhb_module_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR__bhb) },
+    { MP_ROM_QSTR(MP_QSTR_init_adc), MP_ROM_PTR(&_bhb_init_adc_obj) },
+    { MP_ROM_QSTR(MP_QSTR_read_adc), MP_ROM_PTR(&_bhb_read_adc_obj) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(_bhb_module_globals, _bhb_module_globals_table);
+
+const mp_obj_module_t _bhb_user_cmodule = {
+    .base = { &mp_type_module },
+    .globals = (mp_obj_dict_t*)&_bhb_module_globals,
+};
+
+MP_REGISTER_MODULE(MP_QSTR__bhb, _bhb_user_cmodule, MODULE_BHB_ENABLED);

ports/atmel-samd/boards/winterbloom_big_honking_button/usermods/_bhb/micropython.mk

@@ -0,0 +1,6 @@
+USERMODULES_DIR := $(USERMOD_DIR)
+
+# Add all C files to SRC_USERMOD.
+SRC_USERMOD += $(USERMODULES_DIR)/bhb.c
+
+CFLAGS_USERMOD += -I$(USERMODULES_DIR)