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// ADC functions on STM32
//
// Copyright (C) 2019 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);
static const uint32_t adc_pins[][2] = {
{GPIO('A', 0), ADC_CHSELR_CHSEL0},
{GPIO('A', 1), ADC_CHSELR_CHSEL1},
{GPIO('A', 2), ADC_CHSELR_CHSEL2},
{GPIO('A', 3), ADC_CHSELR_CHSEL3},
{GPIO('A', 4), ADC_CHSELR_CHSEL4},
{GPIO('A', 5), ADC_CHSELR_CHSEL5},
{GPIO('A', 6), ADC_CHSELR_CHSEL6},
{GPIO('A', 7), ADC_CHSELR_CHSEL7},
{GPIO('B', 0), ADC_CHSELR_CHSEL8},
{GPIO('B', 1), ADC_CHSELR_CHSEL9},
{GPIO('C', 0), ADC_CHSELR_CHSEL10},
{GPIO('C', 1), ADC_CHSELR_CHSEL11},
{GPIO('C', 2), ADC_CHSELR_CHSEL12},
{GPIO('C', 3), ADC_CHSELR_CHSEL13},
{GPIO('C', 4), ADC_CHSELR_CHSEL14},
{GPIO('C', 5), ADC_CHSELR_CHSEL15}
};
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][0] == pin)
break;
}
// Determine which ADC block to use
ADC_TypeDef *adc = ADC1;
uint32_t adc_base = ADC1_BASE;
// Enable the ADC
if (!is_enabled_pclock(adc_base)) {
enable_pclock(adc_base);
// 100: 41.5 ADC clock cycles
adc->SMPR |= (~ADC_SMPR_SMP_Msk | ADC_SMPR_SMP_2 );
adc->CFGR2 |= ADC_CFGR2_CKMODE;
adc->CFGR1 &= ~ADC_CFGR1_AUTOFF;
adc->CFGR1 |= ADC_CFGR1_EXTSEL;
// do not enable ADC before calibration
adc->CR &= ~ADC_CR_ADEN;
while (adc->CR & ADC_CR_ADEN)
;
while (adc->CFGR1 & ADC_CFGR1_DMAEN)
;
// start calibration and wait for completion
adc->CR |= ADC_CR_ADCAL;
while (adc->CR & ADC_CR_ADCAL)
;
// if not enabled
if (!(adc->CR & ADC_CR_ADEN)){
adc->ISR |= ADC_ISR_ADRDY;
adc->CR |= ADC_CR_ADEN;
while (!(ADC1->ISR & ADC_ISR_ADRDY))
;
}
}
gpio_peripheral(pin, GPIO_ANALOG, 0);
return (struct gpio_adc){ .adc = adc, .chan = adc_pins[chan][1] };
}
// 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 = g.adc;
if ((adc->ISR & ADC_ISR_EOC) && (adc->CHSELR == g.chan)){
return 0;
}
if (adc->CR & ADC_CR_ADSTART){
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 = g.adc;
adc->ISR &= ~ADC_ISR_EOSEQ;
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 = g.adc;
irqstatus_t flag = irq_save();
if (!(adc->ISR & ADC_ISR_EOC) && (adc->CHSELR == g.chan)){
adc->CR |= ADC_CR_ADSTP;
}
irq_restore(flag);
}
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