Dears, i’m working on a LiFi image transmission project using ESP32 microcontrollers.
I then use 2 microcontrollers, one as transmitter through laser and another as receiver through an LDR. So far, the Arduino codes and Python script i’ve used for the transmission aren’t working so far.

• PYTHON CODE TO CONVERT IMAGE TO STRING :

import base64
def image_to_base64(image_path):
with open(image_path, “rb”) as img_file:
img_data = img_file.read()
base64_data = base64.b64encode(img_data)
base64_string = base64_data.decode(“utf-8”)
return base64_string
image_path = “blue.png” # Replace with your image file path
base64_string = image_to_base64(image_path)
print(base64_string)

• ARDUINO CODE TO TRANSFER IMAGE:

#define LED_PIN 22
#define PERIOD 15
char *string =”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#”;
int string_length;
void setup()
{
pinMode(LED_PIN, OUTPUT);
pinMode(3, INPUT);
digitalWrite(3,LOW);
string_length = strlen(string);
delay(5000);
if(digitalRead(3) == HIGH){
for(int i = 0; i < string_length; i ++)
{
send_byte(string[i]);
}
delay(10);
}
}
void loop()

}
void send_byte(char my_byte)
{
digitalWrite(LED_PIN, LOW);
delay(PERIOD);
//transmission of bits
for(int i = 0; i < 8; i++)
{
digitalWrite(LED_PIN, (my_byte&(0x01 << i))!=0 );
delay(PERIOD);
}
digitalWrite(LED_PIN, HIGH);
delay(PERIOD);
}

• PYTHON CODE TO RECEIVE IMAGE:

import serial
import base64
from io import BytesIO
from PIL import Image
import time
import binascii
from serial import Serial
long_string = “”
fixed_base64_str = “”
ser = serial.Serial(‘COM5’, 9600, timeout=15)
ser.reset_input_buffer()
#time.sleep(2)
while True:
if ser.in_waiting > 0:
data = ser.read().decode(‘utf-8’)
long_string += data
print(data, end=””)
if ” ” in long_string:
break
ser.close()
long_string = long_string[:-1]
print(f”nn{long_string}nn”)
Decode the image from the fixed base64 string
image_bytes = base64.b64decode(fixed_base64_str)
image = Image.open(BytesIO(image_bytes))
image.show()

Emission circuit

• ARDUINO CODE TO RECEIVE :

#define LED_PIN 3
#define LDR_PIN 34
#define THRESHOLD 300
#define PERIOD 15
bool previous_state,current_state;
void setup()
{Serial.begin(9600);
pinMode(LED_PIN, OUTPUT);}
void loop()
{current_state = get_ldr();
if(!current_state && previous_state)
{print_byte(get_byte());}
previous_state = current_state;}
bool get_ldr()
{int voltage = analogRead(LDR_PIN);
//Serial.println(voltage);
return voltage > THRESHOLD ? true : false;}
char get_byte()
{char ret = 0;
delay(PERIOD*1.5);
for(int i = 0; i < 8; i++){
ret = ret | get_ldr() << i;
delay(PERIOD);}
return ret;}
void print_byte(char my_byte)
{char buff[2];
sprintf(buff, “%c”, my_byte);
Serial.println(buff);}

RECEPTION CIRCUIT

When i run Python receiver code, i got this error:

Traceback (most recent call last):
  File "C:UsersYasmineAppDataLocalProgramsPythonPython312coderecep.py", line 15, in <module>
    data = ser.read().decode('utf-8')
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe3 in position 0: unexpected end of data

I tried to adjust the synchronisation threshold between 210 and 800, but it did not work..