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// Analog to digital support on lpc176x
//
// Copyright (C) 2018-2019 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "LPC17xx.h" // LPC_PINCON
#include "autoconf.h" // CONFIG_CLOCK_FREQ
#include "board/misc.h" // timer_from_us
#include "command.h" // shutdown
#include "gpio.h" // gpio_adc_setup
#include "internal.h" // gpio_peripheral
#include "sched.h" // sched_shutdown
static const uint8_t adc_pins[] = {
GPIO(0, 23), GPIO(0, 24), GPIO(0, 25), GPIO(0, 26),
GPIO(1, 30), GPIO(1, 31), GPIO(0, 3), GPIO(0, 2),
};
static const uint8_t adc_pin_funcs[] = {
1, 1, 1, 1, 3, 3, 2, 2
};
#define ADC_FREQ_MAX 13000000
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;
}
uint32_t prescal = DIV_ROUND_UP(CONFIG_CLOCK_FREQ*4, ADC_FREQ_MAX) - 1;
uint32_t adcr = (1<<21) | ((prescal & 0xff) << 8);
if (!is_enabled_pclock(PCLK_ADC)) {
// Power up ADC
enable_pclock(PCLK_ADC);
LPC_ADC->ADCR = adcr;
}
gpio_peripheral(pin, adc_pin_funcs[chan], 0);
return (struct gpio_adc){ .cmd = adcr | (1 << chan) | (1 << 24) };
}
static uint32_t adc_status;
// 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 status = adc_status;
if (status == g.cmd) {
// Sample already underway - check if it is ready
uint32_t val = LPC_ADC->ADGDR;
if (val & (1<<31))
// Sample ready
return 0;
goto need_delay;
}
if (status)
// ADC busy on some other channel
goto need_delay;
// Start new sample
adc_status = g.cmd;
LPC_ADC->ADCR = g.cmd;
need_delay:
return (65 * DIV_ROUND_UP(CONFIG_CLOCK_FREQ*4, ADC_FREQ_MAX)
+ 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_status = 0;
return (LPC_ADC->ADGDR >> 4) & 0x0fff;
}
// Cancel a sample that may have been started with gpio_adc_sample()
void
gpio_adc_cancel_sample(struct gpio_adc g)
{
if (adc_status == g.cmd)
adc_status = 0;
}
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