arduino-esp32/libraries/ESP32/examples/I2S/HiFreq_ADC/HiFreq_ADC.ino

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/*
* This is an example to read analog data at high frequency using the I2S peripheral
* Run a wire between pins 27 & 32
* The readings from the device will be 12bit (0-4096)
*/
#include <driver/i2s.h>
#define I2S_SAMPLE_RATE 78125
#define ADC_INPUT ADC1_CHANNEL_4 //pin 32
#define OUTPUT_PIN 27
#define OUTPUT_VALUE 3800
#define READ_DELAY 10000 //microseconds
void i2sInit()
{
i2s_config_t i2s_config = {
.mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_RX | I2S_MODE_ADC_BUILT_IN),
.sample_rate = I2S_SAMPLE_RATE, // The format of the signal using ADC_BUILT_IN
.bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT, // is fixed at 12bit, stereo, MSB
.channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
.communication_format = I2S_COMM_FORMAT_I2S_MSB,
.intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
.dma_buf_count = 4,
.dma_buf_len = 8,
.use_apll = false,
.tx_desc_auto_clear = false,
.fixed_mclk = 0
};
i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);
i2s_set_adc_mode(ADC_UNIT_1, ADC_INPUT);
i2s_adc_enable(I2S_NUM_0);
}
void reader(void *pvParameters) {
uint32_t read_counter = 0;
uint64_t read_sum = 0;
while(1){
size_t bytes_read = 0;
uint16_t buffer = 0;
i2s_read(I2S_NUM_0, &buffer, sizeof(buffer), &bytes_read, portMAX_DELAY);
buffer = ~buffer; // The data is inverted
//Serial.println(buffer % 0x1000);
read_sum += buffer % 0x1000; // The 4 high bits are the channel
read_counter++;
if (bytes_read != sizeof(buffer)) Serial.println("buffer empty!");
if (read_counter == I2S_SAMPLE_RATE) {
Serial.printf("avg: %d\n", read_sum/I2S_SAMPLE_RATE);
read_counter = 0;
read_sum = 0;
i2s_adc_disable(I2S_NUM_0);
delay(READ_DELAY);
i2s_adc_enable(I2S_NUM_0);
}
}
}
void setup() {
Serial.begin(115200);
// Put a signal out on pin
uint32_t freq = ledcSetup(0, I2S_SAMPLE_RATE, 10);
Serial.printf("Output frequency: %d\n", freq);
ledcWrite(0, OUTPUT_VALUE/4);
ledcAttachPin(OUTPUT_PIN, 0);
// Initialize the I2S peripheral
i2sInit();
// Create a task that will read the data
xTaskCreatePinnedToCore(reader, "ADC_reader", 2048, NULL, 1, NULL, 1);
}
void loop() {}