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/*
* MIT License
*
* Copyright (c) 2020 Joey Castillo
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "watch_adc.h"
static void _watch_sync_adc(void) {
while (ADC->SYNCBUSY.reg);
}
static uint16_t _watch_get_analog_value(uint16_t channel) {
if (ADC->INPUTCTRL.bit.MUXPOS != channel) {
ADC->INPUTCTRL.bit.MUXPOS = channel;
_watch_sync_adc();
}
ADC->SWTRIG.bit.START = 1;
while (!ADC->INTFLAG.bit.RESRDY);
return ADC->RESULT.reg;
}
void watch_enable_adc(void) {
MCLK->APBCMASK.reg |= MCLK_APBCMASK_ADC;
GCLK->PCHCTRL[ADC_GCLK_ID].reg = GCLK_PCHCTRL_GEN_GCLK0 | GCLK_PCHCTRL_CHEN;
uint16_t calib_reg = 0;
calib_reg = ADC_CALIB_BIASREFBUF((*(uint32_t *)ADC_FUSES_BIASREFBUF_ADDR >> ADC_FUSES_BIASREFBUF_Pos)) |
ADC_CALIB_BIASCOMP((*(uint32_t *)ADC_FUSES_BIASCOMP_ADDR >> ADC_FUSES_BIASCOMP_Pos));
if (!ADC->SYNCBUSY.bit.SWRST) {
if (ADC->CTRLA.bit.ENABLE) {
ADC->CTRLA.bit.ENABLE = 0;
_watch_sync_adc();
}
ADC->CTRLA.bit.SWRST = 1;
}
_watch_sync_adc();
if (USB->DEVICE.CTRLA.bit.ENABLE) {
// if USB is enabled, we are running an 8 MHz clock.
// divide by 16 for a 500kHz ADC clock.
ADC->CTRLB.bit.PRESCALER = ADC_CTRLB_PRESCALER_DIV16_Val;
} else {
// otherwise it's 4 Mhz. divide by 8 for a 500kHz ADC clock.
ADC->CTRLB.bit.PRESCALER = ADC_CTRLB_PRESCALER_DIV8_Val;
}
ADC->CALIB.reg = calib_reg;
ADC->REFCTRL.bit.REFSEL = ADC_REFCTRL_REFSEL_INTVCC2_Val;
ADC->INPUTCTRL.bit.MUXNEG = ADC_INPUTCTRL_MUXNEG_GND_Val;
ADC->CTRLC.bit.RESSEL = ADC_CTRLC_RESSEL_16BIT_Val;
ADC->AVGCTRL.bit.SAMPLENUM = ADC_AVGCTRL_SAMPLENUM_16_Val;
ADC->SAMPCTRL.bit.SAMPLEN = 0;
ADC->INTENSET.reg = ADC_INTENSET_RESRDY;
ADC->CTRLA.bit.ENABLE = 1;
_watch_sync_adc();
// throw away one measurement after reference change (the channel doesn't matter).
_watch_get_analog_value(ADC_INPUTCTRL_MUXPOS_SCALEDCOREVCC);
}
void watch_enable_analog_input(const uint8_t pin) {
gpio_set_pin_direction(pin, GPIO_DIRECTION_OFF);
switch (pin) {
case A0:
gpio_set_pin_function(pin, PINMUX_PB04B_ADC_AIN12);
break;
case A1:
gpio_set_pin_function(pin, PINMUX_PB01B_ADC_AIN9);
break;
case A2:
gpio_set_pin_function(pin, PINMUX_PB02B_ADC_AIN10);
break;
case A3:
gpio_set_pin_function(pin, PINMUX_PB03B_ADC_AIN11);
break;
case A4:
gpio_set_pin_function(pin, PINMUX_PB00B_ADC_AIN8);
break;
default:
return;
}
}
uint16_t watch_get_analog_pin_level(const uint8_t pin) {
switch (pin) {
case A0:
return _watch_get_analog_value(ADC_INPUTCTRL_MUXPOS_AIN12_Val);
case A1:
return _watch_get_analog_value(ADC_INPUTCTRL_MUXPOS_AIN9_Val);
case A2:
return _watch_get_analog_value(ADC_INPUTCTRL_MUXPOS_AIN10_Val);
case A3:
return _watch_get_analog_value(ADC_INPUTCTRL_MUXPOS_AIN11_Val);
case A4:
return _watch_get_analog_value(ADC_INPUTCTRL_MUXPOS_AIN8_Val);
default:
return 0;
}
}
void watch_set_analog_num_samples(uint16_t samples) {
// ignore any input that's not a power of 2 (i.e. only one bit set)
if (__builtin_popcount(samples) != 1) return;
// if only one bit is set, counting the trailing zeroes is equivalent to log2(samples)
uint8_t sample_val = __builtin_ctz(samples);
// make sure the desired value is within range and set it, if so.
if (sample_val <= ADC_AVGCTRL_SAMPLENUM_1024_Val) {
ADC->AVGCTRL.bit.SAMPLENUM = sample_val;
_watch_sync_adc();
}
}
void watch_set_analog_sampling_length(uint8_t cycles) {
// for clarity the API asks the user how many cycles they want the measurement to take.
// but the ADC always needs at least one cycle; it just wants to know how many *extra* cycles we want.
// so we subtract one from the user-provided value, and clamp to the maximum.
ADC->SAMPCTRL.bit.SAMPLEN = (cycles - 1) & 0x3F;
_watch_sync_adc();
}
void watch_set_analog_reference_voltage(watch_adc_reference_voltage reference) {
ADC->CTRLA.bit.ENABLE = 0;
if (reference == ADC_REFERENCE_INTREF) SUPC->VREF.bit.VREFOE = 1;
else SUPC->VREF.bit.VREFOE = 0;
ADC->REFCTRL.bit.REFSEL = reference;
ADC->CTRLA.bit.ENABLE = 1;
_watch_sync_adc();
// throw away one measurement after reference change (the channel doesn't matter).
_watch_get_analog_value(ADC_INPUTCTRL_MUXPOS_SCALEDCOREVCC);
}
uint16_t watch_get_vcc_voltage(void) {
// stash the previous reference so we can restore it when we're done.
uint8_t oldref = ADC->REFCTRL.bit.REFSEL;
// if we weren't already using the internal reference voltage, select it now.
if (oldref != ADC_REFERENCE_INTREF) watch_set_analog_reference_voltage(ADC_REFERENCE_INTREF);
// get the data
uint32_t raw_val = _watch_get_analog_value(ADC_INPUTCTRL_MUXPOS_SCALEDIOVCC_Val);
// restore the old reference, if needed.
if (oldref != ADC_REFERENCE_INTREF) watch_set_analog_reference_voltage(oldref);
return (uint16_t)((raw_val * 1000) / (1024 * 1 << ADC->AVGCTRL.bit.SAMPLENUM));
}
inline void watch_disable_analog_input(const uint8_t pin) {
gpio_set_pin_function(pin, GPIO_PIN_FUNCTION_OFF);
}
inline void watch_disable_adc(void) {
ADC->CTRLA.bit.ENABLE = 0;
_watch_sync_adc();
MCLK->APBCMASK.reg &= ~MCLK_APBCMASK_ADC;
}
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