kopia lustrzana https://github.com/AlexFWulff/awulff-pico-playground
93 wiersze
2.8 KiB
C++
93 wiersze
2.8 KiB
C++
// Sample from the ADC continuously at a particular sample rate
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// and then outputs base64 bytes via Serial
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// much of this code is from pico-examples/adc/dma_capture/dma_capture.c
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// the rest is written by Alex Wulff (www.AlexWulff.com)
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#include <stdio.h>
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#include <cstring>
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#include "pico/stdlib.h"
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#include "hardware/adc.h"
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#include "hardware/dma.h"
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#include "base64.h"
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// set this to determine sample rate
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// 0 = 500,000 Hz
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// 960 = 50,000 Hz
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// 9600 = 5,000 Hz
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#define CLOCK_DIV 9600
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// Channel 0 is GPIO26
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#define CAPTURE_CHANNEL 0
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#define LED_PIN 25
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#define NSAMP 20000
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uint16_t capture_buf[NSAMP];
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uint16_t sending_buf[NSAMP];
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int main() {
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stdio_init_all();
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gpio_init(LED_PIN);
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gpio_set_dir(LED_PIN, GPIO_OUT);
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adc_gpio_init(26 + CAPTURE_CHANNEL);
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adc_init();
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adc_select_input(CAPTURE_CHANNEL);
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adc_fifo_setup(
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true, // Write each completed conversion to the sample FIFO
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true, // Enable DMA data request (DREQ)
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1, // DREQ (and IRQ) asserted when at least 1 sample present
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false, // We won't see the ERR bit because of 8 bit reads; disable.
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false // Don't shift each sample to 8 bits when pushing to FIFO
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);
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// set sample rate
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adc_set_clkdiv(CLOCK_DIV);
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sleep_ms(1000);
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// Set up the DMA to start transferring data as soon as it appears in FIFO
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uint dma_chan = dma_claim_unused_channel(true);
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dma_channel_config cfg = dma_channel_get_default_config(dma_chan);
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// Reading from constant address, writing to incrementing byte addresses
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channel_config_set_transfer_data_size(&cfg, DMA_SIZE_16);
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channel_config_set_read_increment(&cfg, false);
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channel_config_set_write_increment(&cfg, true);
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// Pace transfers based on availability of ADC samples
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channel_config_set_dreq(&cfg, DREQ_ADC);
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while (1) {
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adc_fifo_drain();
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adc_run(false);
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dma_channel_configure(dma_chan, &cfg,
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capture_buf, // dst
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&adc_hw->fifo, // src
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NSAMP, // transfer count
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true // start immediately
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);
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// if the light does not flash, then there is some data loss.
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// pico can't print the data out fast enough, so the capturing
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// finishes before the data is done printing. This will result
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// in the ADC not collecting for portions of the sampling
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// run sampling routine
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gpio_put(LED_PIN, 1);
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adc_run(true);
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// first transmission will be garbage since we haven't filled the buffer yet
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std::string encoded =
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base64_encode((unsigned char const *)sending_buf, NSAMP*2);
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printf("%s", encoded.c_str());
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gpio_put(LED_PIN, 0);
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dma_channel_wait_for_finish_blocking(dma_chan);
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memcpy(sending_buf, capture_buf, NSAMP*2);
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}
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}
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