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// Analog to digital conversion (ADC) code on PRU
//
// Copyright (C) 2017 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "board/io.h" // readl
#include "command.h" // shutdown
#include "compiler.h" // ARRAY_SIZE
#include "gpio.h" // gpio_adc_setup
#include "internal.h" // ADC
#include "sched.h" // sched_shutdown
/****************************************************************
* Analog to Digital Converter (ADC) pins
****************************************************************/
DECL_CONSTANT("ADC_MAX", 4095);
static void
adc_full_reset(void)
{
static uint8_t have_done_reset;
if (have_done_reset)
return;
// Disable ADC
ADC->ctrl = (1<<2);
barrier();
// Clear registers
ADC->irqstatus = 0xffffffff;
ADC->irqenable_clr = 0xffffffff;
ADC->dmaenable_clr = 0xffffffff;
ADC->adc_clkdiv = 0;
ADC->stepenable = 0;
ADC->idleconfig = 0;
int i;
for (i=0; i<8; i++) {
ADC->step[i].config = i<<19;
ADC->step[i].delay = 0;
}
// Enable ADC
writel(&ADC->ctrl, 0x07);
// Drain fifo
while (readl(&ADC->fifo0count))
readl(&ADC->fifo0data);
if (!readl(&ADC->ctrl))
shutdown("ADC module not enabled");
have_done_reset = 1;
}
DECL_ENUMERATION_RANGE("pin", "AIN0", 4 * 32, 8);
struct gpio_adc
gpio_adc_setup(uint8_t pin)
{
uint8_t chan = pin - 4 * 32;
if (chan >= 8)
shutdown("Not an adc channel");
adc_full_reset();
return (struct gpio_adc){ .chan = chan };
}
enum { ADC_DUMMY=0xff };
static uint8_t last_analog_read = ADC_DUMMY;
static uint16_t last_analog_sample;
// 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)
{
uint8_t last = last_analog_read;
if (last == ADC_DUMMY) {
// Start sample
last_analog_read = g.chan;
writel(&ADC->stepenable, 1 << (g.chan + 1));
goto need_delay;
}
if (last == g.chan) {
// Check if sample ready
while (readl(&ADC->fifo0count)) {
uint32_t sample = readl(&ADC->fifo0data);
if (sample >> 16 == g.chan) {
last_analog_read = ADC_DUMMY;
last_analog_sample = sample;
return 0;
}
}
}
need_delay:
return 160;
}
// Read a value; use only after gpio_adc_sample() returns zero
uint16_t
gpio_adc_read(struct gpio_adc g)
{
return last_analog_sample;
}
// 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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