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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[] = {
#if CONFIG_MACH_SAM3X
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)
#elif CONFIG_MACH_SAM4S
GPIO('A', 17), GPIO('A', 18), GPIO('A', 19), GPIO('A', 20),
GPIO('B', 0), GPIO('B', 1), GPIO('B', 2), GPIO('B', 3),
GPIO('A', 21), GPIO('A', 22), GPIO('C', 13), GPIO('C', 15),
GPIO('C', 12), GPIO('C', 29), GPIO('C', 30)
#endif
};
#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 (!is_enabled_pclock(ID_ADC)) {
// Setup ADC
enable_pclock(ID_ADC);
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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