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// ADC functions on STM32
//
// Copyright (C) 2019-2020 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "board/irq.h" // irq_save
#include "board/misc.h" // timer_from_us
#include "command.h" // shutdown
#include "compiler.h" // ARRAY_SIZE
#include "generic/armcm_timer.h" // udelay
#include "gpio.h" // gpio_adc_setup
#include "internal.h" // GPIO
#include "sched.h" // sched_shutdown
DECL_CONSTANT("ADC_MAX", 4095);
#define ADC_TEMPERATURE_PIN 0xfe
DECL_ENUMERATION("pin", "ADC_TEMPERATURE", ADC_TEMPERATURE_PIN);
static const uint8_t adc_pins[] = {
GPIO('A', 0), GPIO('A', 1), GPIO('A', 2), GPIO('A', 3),
GPIO('A', 4), GPIO('A', 5), GPIO('A', 6), GPIO('A', 7),
GPIO('B', 0), GPIO('B', 1), GPIO('C', 0), GPIO('C', 1),
GPIO('C', 2), GPIO('C', 3), GPIO('C', 4), GPIO('C', 5),
ADC_TEMPERATURE_PIN
};
struct gpio_adc
gpio_adc_setup(uint32_t pin)
{
// Find pin in adc_pins table
int chan;
for (chan=0; ; chan++) {
if (chan >= ARRAY_SIZE(adc_pins))
shutdown("Not a valid ADC pin");
if (adc_pins[chan] == pin)
break;
}
// Enable the ADC
if (!is_enabled_pclock(ADC1_BASE)) {
enable_pclock(ADC1_BASE);
ADC_TypeDef *adc = ADC1;
// 100: 41.5 ADC clock cycles
adc->SMPR = 4 << ADC_SMPR_SMP_Pos;
// start calibration and wait for completion
adc->CR = ADC_CR_ADCAL;
while (adc->CR & ADC_CR_ADCAL)
;
adc->ISR = ADC_ISR_ADRDY;
adc->CR = ADC_CR_ADEN;
while (!(adc->ISR & ADC_ISR_ADRDY))
;
}
if (pin == ADC_TEMPERATURE_PIN)
ADC1_COMMON->CCR = ADC_CCR_TSEN;
else
gpio_peripheral(pin, GPIO_ANALOG, 0);
return (struct gpio_adc){ .chan = 1 << chan };
}
// Try to sample a value. Returns zero if sample ready, otherwise
// returns the number of clock ticks the caller should wait before
// retrying this function.
uint32_t
gpio_adc_sample(struct gpio_adc g)
{
ADC_TypeDef *adc = ADC1;
if (adc->CR & ADC_CR_ADSTART)
goto need_delay;
if (adc->ISR & ADC_ISR_EOC) {
if (adc->CHSELR == g.chan)
return 0;
goto need_delay;
}
adc->CHSELR = g.chan;
adc->CR = ADC_CR_ADSTART;
need_delay:
return timer_from_us(10);
}
// Read a value; use only after gpio_adc_sample() returns zero
uint16_t
gpio_adc_read(struct gpio_adc g)
{
ADC_TypeDef *adc = ADC1;
return adc->DR;
}
// Cancel a sample that may have been started with gpio_adc_sample()
void
gpio_adc_cancel_sample(struct gpio_adc g)
{
ADC_TypeDef *adc = ADC1;
irqstatus_t flag = irq_save();
if (adc->CHSELR == g.chan) {
if (adc->CR & ADC_CR_ADSTART)
adc->CR = ADC_CR_ADSTP;
if (adc->ISR & ADC_ISR_EOC)
gpio_adc_read(g);
}
irq_restore(flag);
}
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