Reworked HiFreq_ADC example; Closing #6832

libraries/ESP32/examples/I2S/HiFreq_ADC/HiFreq_ADC.ino

@@ -1,83 +1,133 @@
 /*
- * 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) 
- */
+  This example demonstrates I2S ADC capability to sample high frequency analog signals.
+  The PWM signal generated with ledc is only for ease of use when first trying out.
+  To sample the generated signal connect default pins 27(PWM) and 32(Sampling) together.
+  If you do not wish to generate PWM simply comment out the definition of constant GENERATE_PWM
+  Try to change the PWM_DUTY_PERCENT and see how to averaged value changes.
+
+  The maximum for I2S ADC sampling frequency is 5MHz (value 5000000), however there will be many values repeated because the real
+  sampling frequency is much lower -
+
+  By default this example will print values compatible with Arduino plotter
+  1. signal - all values
+  2. signal - averaged value
+
+  You can change the number of sample over which is the signal averaged by changing value of AVERAGE_EVERY_N_SAMPLES
+  If you comment the definition altogether the averaging will not be performed nor printed.
+
+  If you do not wish to print every value, simply comment definition of constant PRINT_ALL_VALUES
+
+  Note: ESP prints messages at startup which will pollute Arduino IDE Serial plotter legend.
+  To avoid this pollution, start the plotter after startup (op restart)
+*/
 #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 9000 //microseconds
+// I2S
+#define I2S_SAMPLE_RATE (277777) // Max sampling frequency = 277.777 kHz
+#define ADC_INPUT (ADC1_CHANNEL_4) //pin 32
+#define I2S_DMA_BUF_LEN (1024)
+
+// PWM
+#define GENERATE_PWM
+#define OUTPUT_PIN (27)
+#define PWM_FREQUENCY ((I2S_SAMPLE_RATE)/4)
+#define PWM_DUTY_PERCENT (50)
+#define PWM_RESOLUTION_BITS (2) // Lower bit resolution enables higher frequency
+#define PWM_DUTY_VALUE ((((1<<(PWM_RESOLUTION_BITS)))*(PWM_DUTY_PERCENT))/100) // Duty value used for setup function based on resolution
 
-uint16_t adc_reading;
+// Sample post processing
+#define PRINT_ALL_VALUES
+#define AVERAGE_EVERY_N_SAMPLES (100)
 
-void i2sInit()
-{
-   i2s_config_t i2s_config = {
+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,
+    .communication_format = I2S_COMM_FORMAT_STAND_I2S,
     .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
-    .dma_buf_count = 4,
-    .dma_buf_len = 8,
+    .dma_buf_count = 8,
+    .dma_buf_len = I2S_DMA_BUF_LEN,
     .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);
-}
+  };
+  Serial.printf("Attempting to setup I2S ADC with sampling frequency %d Hz\n", I2S_SAMPLE_RATE);
+  if(ESP_OK != i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL)){
+    Serial.printf("Error installing I2S. Halt!");
+    while(1);
+  }
+  if(ESP_OK != i2s_set_adc_mode(ADC_UNIT_1, ADC_INPUT)){
+    Serial.printf("Error setting up ADC. Halt!");
+    while(1);
+  }
+  if(ESP_OK != adc1_config_channel_atten(ADC_INPUT, ADC_ATTEN_DB_11)){
+    Serial.printf("Error setting up ADC attenuation. Halt!");
+    while(1);
+  }
 
-void reader(void *pvParameters) {
-  uint32_t read_counter = 0;
-  uint64_t read_sum = 0;
-// The 4 high bits are the channel, and the data is inverted
-  uint16_t offset = (int)ADC_INPUT * 0x1000 + 0xFFF;
-  size_t bytes_read;
-  while(1){
-    uint16_t buffer[2] = {0};
-    i2s_read(I2S_NUM_0, &buffer, sizeof(buffer), &bytes_read, 15);
-    //Serial.printf("%d  %d\n", offset - buffer[0], offset - buffer[1]);
-    if (bytes_read == sizeof(buffer)) {
-      read_sum += offset - buffer[0];
-      read_sum += offset - buffer[1];
-      read_counter++;
-    } else {
-      Serial.println("buffer empty");
-    }
-    if (read_counter == I2S_SAMPLE_RATE) {
-      adc_reading = read_sum / I2S_SAMPLE_RATE / 2;
-      //Serial.printf("avg: %d millis: ", adc_reading);
-      //Serial.println(millis());
-      read_counter = 0;
-      read_sum = 0;
-      i2s_adc_disable(I2S_NUM_0);
-      delay(READ_DELAY);
-      i2s_adc_enable(I2S_NUM_0);
-    }
+  if(ESP_OK != i2s_adc_enable(I2S_NUM_0)){
+    Serial.printf("Error enabling ADC. Halt!");
+    while(1);
   }
+  Serial.printf("I2S ADC setup ok\n");
 }
 
 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);
+
+#ifdef GENERATE_PWM
+  // PWM setup
+  Serial.printf("Setting up PWM: frequency = %d; resolution bits %d; Duty cycle = %d; duty value = %d, Output pin = %d\n", PWM_FREQUENCY, PWM_RESOLUTION_BITS, PWM_DUTY_PERCENT, PWM_DUTY_VALUE, OUTPUT_PIN);
+  uint32_t freq = ledcSetup(0, PWM_FREQUENCY, PWM_RESOLUTION_BITS);
+  if(freq != PWM_FREQUENCY){
+    Serial.printf("Error setting up PWM. Halt!");
+    while(1);
+  }
   ledcAttachPin(OUTPUT_PIN, 0);
+  ledcWrite(0, PWM_DUTY_VALUE);
+  Serial.printf("PWM setup ok\n");
+#endif
+
   // Initialize the I2S peripheral
   i2sInit();
-  // Create a task that will read the data
-  xTaskCreatePinnedToCore(reader, "ADC_reader", 2048, NULL, 1, NULL, 1);
 }
 
-void loop() {
-  delay(1020);
-  Serial.printf("ADC reading: %d\n", adc_reading);
-  delay(READ_DELAY);
+void loop(){
+// The 4 high bits are the channel, and the data is inverted
+  size_t bytes_read;
+  uint16_t buffer[I2S_DMA_BUF_LEN] = {0};
+
+#ifdef AVERAGE_EVERY_N_SAMPLES
+  uint32_t read_counter = 0;
+  uint32_t averaged_reading = 0;
+  uint64_t read_sum = 0;
+#endif
+
+  while(1){
+    i2s_read(I2S_NUM_0, &buffer, sizeof(buffer), &bytes_read, 15);
+    //Serial.printf("read %d Bytes\n", bytes_read);
+
+    for(int i = 0; i < bytes_read/2; ++i){
+#ifdef PRINT_ALL_VALUES
+      //Serial.printf("[%d] = %d\n", i, buffer[i] & 0x0FFF); // Print with indexes
+      Serial.printf("Signal:%d ", buffer[i] & 0x0FFF); // Print compatible with Arduino Plotter
+#endif
+#ifdef AVERAGE_EVERY_N_SAMPLES
+      read_sum += buffer[i] & 0x0FFF;
+      ++read_counter;
+      if(read_counter == AVERAGE_EVERY_N_SAMPLES){
+        averaged_reading = read_sum / AVERAGE_EVERY_N_SAMPLES;
+        //Serial.printf("averaged_reading = %d over %d samples\n", averaged_reading, read_counter); // Print with additional info
+        Serial.printf("Averaged_signal:%d", averaged_reading); // Print compatible with Arduino Plotter
+        read_counter = 0;
+        read_sum = 0;
+      }
+#endif
+#if defined(PRINT_ALL_VALUES) || defined (AVERAGE_EVERY_N_SAMPLES)
+      Serial.printf("\n");
+#endif
+    } // for
+  } // while
 }