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// ADC functions on rp2040
//
// Copyright (C) 2021 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "board/misc.h" // timer_from_us
#include "command.h" // shutdown
#include "gpio.h" // gpio_adc_setup
#include "hardware/structs/adc.h" // adc_hw
#include "hardware/structs/padsbank0.h" // padsbank0_hw
#include "hardware/structs/resets.h" // RESETS_RESET_ADC_BITS
#include "internal.h" // enable_pclock
#include "sched.h" // sched_shutdown
DECL_CONSTANT("ADC_MAX", 4095);
#define ADC_TEMPERATURE_PIN 0xfe
DECL_ENUMERATION("pin", "ADC_TEMPERATURE", ADC_TEMPERATURE_PIN);
struct gpio_adc
gpio_adc_setup(uint32_t pin)
{
if ((pin < 26 || pin > 29) && pin != ADC_TEMPERATURE_PIN)
shutdown("Not a valid ADC pin");
// Enable the ADC
if (!is_enabled_pclock(RESETS_RESET_ADC_BITS)) {
enable_pclock(RESETS_RESET_ADC_BITS);
adc_hw->cs = ADC_CS_EN_BITS;
}
uint8_t chan;
if (pin == ADC_TEMPERATURE_PIN) {
chan = 4;
adc_hw->cs |= ADC_CS_TS_EN_BITS;
} else {
chan = pin - 26;
padsbank0_hw->io[pin] = PADS_BANK0_GPIO0_OD_BITS;
}
return (struct gpio_adc){ .chan = chan };
}
enum { ADC_DUMMY=0xff };
static uint8_t last_analog_read = ADC_DUMMY;
// 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 cs = adc_hw->cs;
if (!(cs & ADC_CS_READY_BITS))
// ADC is busy
goto need_delay;
if (last_analog_read == g.chan)
// Sample now ready
return 0;
if (last_analog_read != ADC_DUMMY)
// Sample on another channel in progress
goto need_delay;
// Begin sample
last_analog_read = g.chan;
adc_hw->cs = ((cs & ADC_CS_TS_EN_BITS) | ADC_CS_START_ONCE_BITS
| ADC_CS_EN_BITS | (g.chan << ADC_CS_AINSEL_LSB));
need_delay:
return timer_from_us(5); // Sample takes 2us but provide extra time
}
// Read a value; use only after gpio_adc_sample() returns zero
uint16_t
gpio_adc_read(struct gpio_adc g)
{
last_analog_read = ADC_DUMMY;
return adc_hw->result;
}
// Cancel a sample that may have been started with gpio_adc_sample()
void
gpio_adc_cancel_sample(struct gpio_adc g)
{
if (last_analog_read == g.chan)
last_analog_read = ADC_DUMMY;
}
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