pySerial killing arduino program

[jbg73]

Hi everyone,

Introduction & Purpose
I've recently bought the ESP32-CAM as well as the ESP32-CAM-MB (ESP32-CAM Introduction). My aim is to create an Arduino program that takes a still every 5 seconds and then writes its pixel values via Serial port. On the other hand, I want to have a python program that reads the serial port in order to gather this data, so that I could then display the image by using PIL library.

Current approach
I now have the following:

• Arduino program that takes the still and writes its pixel values to the Serial Port:

#include <esp_camera.h>

#define CAMERA_MODEL_AI_THINKER

#include "camera_pins.h"


#define FRAME_SIZE FRAMESIZE_240X240
#define WIDTH 240
#define HEIGHT 240

#define FLASH_PIN 4


uint8_t img_array_1D [HEIGHT][WIDTH];

bool setup_camera(framesize_t);
bool capture_image();
void display_img();
void set_flash(int);

void setup(){
  Serial.begin(115200);
  setup_camera(FRAME_SIZE);
  // //Serial.println(setup_camera(FRAME_SIZE) ? "Camera initialized OK!" : "Error initing camera!");
  pinMode(FLASH_PIN, OUTPUT);
}

void loop(){
  //Serial.println("Take new image");
  if(!capture_image()){
    //Serial.println("Failed capturing image");
    delay(2000);

    return;
  }
  delay(5000); // Take still every 10 secs
}

bool setup_camera(framesize_t frameSize){
  camera_config_t config;

  config.ledc_channel = LEDC_CHANNEL_0;
  config.ledc_timer = LEDC_TIMER_0;
  config.pin_d0 = Y2_GPIO_NUM;
  config.pin_d1 = Y3_GPIO_NUM;
  config.pin_d2 = Y4_GPIO_NUM;
  config.pin_d3 = Y5_GPIO_NUM;
  config.pin_d4 = Y6_GPIO_NUM;
  config.pin_d5 = Y7_GPIO_NUM;
  config.pin_d6 = Y8_GPIO_NUM;
  config.pin_d7 = Y9_GPIO_NUM;
  config.pin_xclk = XCLK_GPIO_NUM;
  config.pin_pclk = PCLK_GPIO_NUM;
  config.pin_vsync = VSYNC_GPIO_NUM;
  config.pin_href = HREF_GPIO_NUM;
  config.pin_sscb_sda = SIOD_GPIO_NUM;
  config.pin_sscb_scl = SIOC_GPIO_NUM;
  config.pin_pwdn = PWDN_GPIO_NUM;
  config.pin_reset = RESET_GPIO_NUM;
  config.xclk_freq_hz = 20000000;
  config.pixel_format = PIXFORMAT_GRAYSCALE;
  config.frame_size = frameSize;
  config.jpeg_quality = 12;
  config.fb_count = 1;

  bool ok = esp_camera_init(&config) == ESP_OK;

  sensor_t *sensor = esp_camera_sensor_get();
  sensor->set_framesize(sensor, frameSize);

  return ok;
}

bool capture_image() {
  
  camera_fb_t * frame = NULL;
  frame = esp_camera_fb_get();
  print_image_shape(frame);

  frame_to_array(frame);

  // display_img();

  esp_camera_fb_return(frame);

  if (!frame){
    //Serial.println("Something went wrong with the camera");
    return false;

  }

  return true;
 }


void print_image_shape(camera_fb_t * frame){

  // print shape of image and total length (=heigth*width)
  //Serial.print("Width: ");
  //Serial.print(frame->width);
  //Serial.print("\tHeigth: ");
  //Serial.print(frame->height);
  //Serial.print("\tLength: ");
  //Serial.println(frame->len);
 }


void frame_to_array(camera_fb_t * frame){

  int len = frame->len;
  char imgBuffer[frame->len];
  int counter = 0;

  // uint16_t img_array_1D [HEIGHT][WIDTH] = { 0 };

  int h_counter = 0;
  int w_counter = 0;

  // write values from buffer into 2D Array
  for (int h=0; h < HEIGHT; h++){
    ////Serial.println(h);
    for (int w=0; w < WIDTH; w++){
      ////Serial.println(w);
      int position = h*(len/HEIGHT)+w;

      // Serial.println(frame->buf[position]);
      img_array_1D[h][w] = frame->buf[position];
      // display_img();
      Serial.print(img_array_1D[h][w]);
      ////Serial.print(",");
      //delay(2);
    }
  }
  Serial.println("Finished image processing");
  set_flash(5);


  ////Serial.println("Current frame:");

  //Serial.println("=====================");

 }

void display_img(){
  for(int h = 0; h < HEIGHT; h++){
    for(int w = 0; w < WIDTH; w++){
      //Serial.print(img_array_1D[h][w] + ",");
    }
  }
}

void set_flash(int msecs){
  digitalWrite(FLASH_PIN, HIGH);
  delay(msecs);
  digitalWrite(FLASH_PIN, LOW);
  delay(msecs);
}

• Python program that opens the Serial port and reads its data:

import time
import serial

def display_img(img_data):
    print("Displaying data...")
    for i in range(len(img_data)):
        print(img_data[i])

def read_serial_data(arduino_serial):
    if not arduino_serial.is_open:
        arduino_serial.open()

    if arduino_serial.is_open:
        arduino_serial.inWaiting()
        img_data = arduino_serial.readline().decode("utf-8").replace("\r\n", "").split(",")
        display_img(img_data)
        return img_data

def main():
    print("Initing main program...")
    arduino_serial = serial.Serial('COM4', 115200)
    time.sleep(5)
    while True:
        img_data = read_serial_data(arduino_serial)

if __name__ == '__main__':
    main()

Expected behaviour
Everytime a still is taken, its pixel values are printed to the serial port and the python code reads them and displays them on the terminal.

Actual behaviour
I know that the arduino program works fine as I make the led "flash" every time it ends printing the data to the Serial port, however, as soon as I run the python code, and the statement

arduino_serial = serial.Serial('COM4', 115200)

is executed, the Arduino program seems to be killed, as the led is no longer flashing, so I guess it is neither printing anything to the Serial port. The again, if I stop the python code, the led begins to flash again, that's why I concluded (maybe naïvely) that the python code is killing the Arduino one.

Has any of you experienced anything similar? I am quite confused, because I've done this serial communication before with other boards and programs and it's always worked fine.

Thanks for reading
Any help is of great aid!

[MrY]

Check this tutorial on serial comms using python: Demo of PC-Arduino comms using Python

[Idahowalker]

Can FTP server be run on the target?

[jremington]

If you don't use this array for anything other than printing one byte at a time, it does take up some memory.

      img_array_1D[h][w] = frame->buf[position];
      // display_img();
      Serial.print(img_array_1D[h][w]);