100 lines
2.8 KiB
C
100 lines
2.8 KiB
C
// Analog to digital support
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//
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// Copyright (C) 2016-2018 Kevin O'Connor <kevin@koconnor.net>
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//
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// This file may be distributed under the terms of the GNU GPLv3 license.
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#include "autoconf.h" // CONFIG_CLOCK_FREQ
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#include "board/irq.h" // irq_save
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#include "command.h" // shutdown
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#include "compiler.h" // ARRAY_SIZE
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#include "gpio.h" // gpio_adc_setup
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#include "internal.h" // GPIO
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#include "sched.h" // sched_shutdown
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static const uint8_t adc_pins[] = {
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#if CONFIG_MACH_SAM3X
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GPIO('A', 2), GPIO('A', 3), GPIO('A', 4), GPIO('A', 6),
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GPIO('A', 22), GPIO('A', 23), GPIO('A', 24), GPIO('A', 16),
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GPIO('B', 12), GPIO('B', 13), GPIO('B', 17), GPIO('B', 18),
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GPIO('B', 19), GPIO('B', 20)
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#elif CONFIG_MACH_SAM4S
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GPIO('A', 17), GPIO('A', 18), GPIO('A', 19), GPIO('A', 20),
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GPIO('B', 0), GPIO('B', 1), GPIO('B', 2), GPIO('B', 3),
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GPIO('A', 21), GPIO('A', 22), GPIO('C', 13), GPIO('C', 15),
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GPIO('C', 12), GPIO('C', 29), GPIO('C', 30)
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#endif
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};
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#define ADC_FREQ_MAX 20000000
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DECL_CONSTANT("ADC_MAX", 4095);
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struct gpio_adc
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gpio_adc_setup(uint8_t pin)
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{
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// Find pin in adc_pins table
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int chan;
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for (chan=0; ; chan++) {
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if (chan >= ARRAY_SIZE(adc_pins))
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shutdown("Not a valid ADC pin");
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if (adc_pins[chan] == pin)
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break;
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}
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if (!is_enabled_pclock(ID_ADC)) {
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// Setup ADC
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enable_pclock(ID_ADC);
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uint32_t prescal = SystemCoreClock / (2 * ADC_FREQ_MAX) - 1;
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ADC->ADC_MR = (ADC_MR_PRESCAL(prescal)
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| ADC_MR_STARTUP_SUT768
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| ADC_MR_TRANSFER(1));
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}
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// Place pin in input floating mode
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gpio_in_setup(pin, 0);
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return (struct gpio_adc){ .chan = 1 << chan };
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}
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// Try to sample a value. Returns zero if sample ready, otherwise
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// returns the number of clock ticks the caller should wait before
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// retrying this function.
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uint32_t
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gpio_adc_sample(struct gpio_adc g)
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{
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uint32_t chsr = ADC->ADC_CHSR & 0xffff;
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if (!chsr) {
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// Start sample
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ADC->ADC_CHER = g.chan;
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ADC->ADC_CR = ADC_CR_START;
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goto need_delay;
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}
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if (chsr != g.chan)
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// Sampling in progress on another channel
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goto need_delay;
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if (!(ADC->ADC_ISR & ADC_ISR_DRDY))
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// Conversion still in progress
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goto need_delay;
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// Conversion ready
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return 0;
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need_delay:
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return ADC_FREQ_MAX * 1000ULL / CONFIG_CLOCK_FREQ;
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}
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// Read a value; use only after gpio_adc_sample() returns zero
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uint16_t
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gpio_adc_read(struct gpio_adc g)
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{
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ADC->ADC_CHDR = g.chan;
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return ADC->ADC_LCDR;
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}
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// Cancel a sample that may have been started with gpio_adc_sample()
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void
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gpio_adc_cancel_sample(struct gpio_adc g)
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{
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irqstatus_t flag = irq_save();
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if ((ADC->ADC_CHSR & 0xffff) == g.chan)
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gpio_adc_read(g);
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irq_restore(flag);
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}
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