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// Analog to digital support
//
// Copyright (C) 2016-2018 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "autoconf.h" // CONFIG_CLOCK_FREQ
#include "board/irq.h" // irq_save
#include "command.h" // shutdown
#include "compiler.h" // ARRAY_SIZE
#include "gpio.h" // gpio_adc_setup
#include "internal.h" // GPIO
#include "sched.h" // sched_shutdown
static const uint8_t adc_pins[] = {
GPIO('A', 2), GPIO('A', 3), GPIO('A', 4), GPIO('A', 6),
GPIO('A', 22), GPIO('A', 23), GPIO('A', 24), GPIO('A', 16),
GPIO('B', 12), GPIO('B', 13), GPIO('B', 17), GPIO('B', 18),
GPIO('B', 19), GPIO('B', 20)
};
#define ADC_FREQ_MAX 20000000
DECL_CONSTANT(ADC_MAX, 4095);
struct gpio_adc
gpio_adc_setup(uint8_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;
}
if (!(PMC->PMC_PCSR1 & (1 << (ID_ADC-32)))) {
// Setup ADC
PMC->PMC_PCER1 = 1 << (ID_ADC-32);
uint32_t prescal = SystemCoreClock / (2 * ADC_FREQ_MAX) - 1;
ADC->ADC_MR = (ADC_MR_PRESCAL(prescal)
| ADC_MR_STARTUP_SUT768
| ADC_MR_TRANSFER(1));
}
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)
{
uint32_t chsr = ADC->ADC_CHSR & 0xffff;
if (!chsr) {
// Start sample
ADC->ADC_CHER = g.chan;
ADC->ADC_CR = ADC_CR_START;
goto need_delay;
}
if (chsr != g.chan)
// Sampling in progress on another channel
goto need_delay;
if (!(ADC->ADC_ISR & ADC_ISR_DRDY))
// Conversion still in progress
goto need_delay;
// Conversion ready
return 0;
need_delay:
return ADC_FREQ_MAX * 1000ULL / CONFIG_CLOCK_FREQ;
}
// Read a value; use only after gpio_adc_sample() returns zero
uint16_t
gpio_adc_read(struct gpio_adc g)
{
ADC->ADC_CHDR = g.chan;
return ADC->ADC_LCDR;
}
// Cancel a sample that may have been started with gpio_adc_sample()
void
gpio_adc_cancel_sample(struct gpio_adc g)
{
irqstatus_t flag = irq_save();
if ((ADC->ADC_CHSR & 0xffff) == g.chan)
gpio_adc_read(g);
irq_restore(flag);
}
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