As said in Title , I am making morse coder/decoder with 2 arduino. I have 2 codes, one is for sending sign and the other one is for decoding sign.
Links of codes here:
DECODER
CODER
When I try to send lets say : E sign in morse it decodes sometimes B and sometimes some other letter.
I used serial monitor for the CODER to see if it prits out good letter and it does, I think its the problem in DECODER but I cant seem to figure it out .
If anyone know smth thank you for your answers 
Please post your code here
DECODER
int LDR_Pin = A0; //analog pin 0
int led = 13;
int LDR_Maxvalue=800;
int dot_length=800;
int dash_length=2500;
int letter_pause=2400;
#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
// 10k between GND and A0
// LDR between 5V and A0
void setup(){
Serial.begin(9600);
pinMode(led, OUTPUT);
lcd.begin(16,2);
}
int counter_high = 0;
int counter_low = 0;
void loop(){
int LDRReading = analogRead(LDR_Pin);
if (LDRReading >= LDR_Maxvalue){
counter_high++ ;
if ( counter_low > 0 ){
// Serial.print("Low\t");
// Serial.print(counter_low);
// Serial.print("\n");
}
if ( counter_low >= letter_pause) {
Serial.println();
lcd.setCursor(0, 0);
}
counter_low=0;
digitalWrite(led, HIGH);
}
else {
// Serial.print(".");
counter_low++;
if ( counter_high > 0 ){
// Serial.print("High\t");
// Serial.print(counter_high);
}
if ( (counter_high <= letter_pause ) &&( counter_high >=dot_length)){
// Serial.print(counter_high);
Serial.print(".");
lcd.print(".");
}
if ( counter_high > letter_pause ){
// Serial.print(counter_high);
Serial.print("-");
lcd.print("-");
}
counter_high=0;
digitalWrite(led, LOW);
}
}
CODER
const int ledPin = 13;
int unit = 250;
char* morseLet[]= {".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..", ".---", "-.-", ".-..", "--", "-.", "---", ".--.", "--.-", ".-.", "...", "-", "..-", "...-", ".--", "-..-", "-.--", "--.."};
char* morseNum[]= {"-----", ".----", "..---", "...--", "....-", ".....", "-....", "--...", "---..", "----."};
void setup() {
pinMode(ledPin, OUTPUT);
delay(1000);
Serial.begin(9600);
}
void loop() {
char info;
if(Serial.available() >0) {
info = Serial.read();
if(info >= 'a' && info <= 'z'){
interp(morseLet[info - 'a']);
}
else if(info >= 'A' && info <= 'Z'){
interp(morseLet[info - 'A']);
}
else if(info >= '0' && info <= '9'){
interp(morseLet[info - 0]);
}
else if (info== ' '){
delay(unit*7);
}
}
}
void interp(char* character){
int i=0;
while (character[i] != '\0'){
output (character[i]);
i++;
}
delay (unit*3);
}
void output(char outp){
digitalWrite(ledPin, HIGH);
if(outp =='.') {
delay(unit);
}
else {
delay(unit*3);
}
digitalWrite(ledPin, LOW);
delay(unit);
}
It is very likely that there are timing errors in the receive code.
LDRs are very slow, and you forgot to mention how you arrived at the possibly inaccurate mystery constants:
int LDR_Maxvalue=800;
int dot_length=800;
int dash_length=2500;
int letter_pause=2400;
Why is dash_length not 3 dot lengths?
Thank you for your answer.
dot_length is length of dot state in LED and you are right that there should be dash_length 2400, and letter_pause is pause between letters time when diode is turned off.
Shall I use another approach for timing domain?
ye i got it , will try to do
when i put timers on 800ms it is not reacting , program not working . I give up hahaha 
I give up hahaha
OK. Have a nice life!
Generally, the receiver code would be something like
uint32_t startMs;
char buf[20];
char bufct = 0;
boolean we_might_need_to_handle_a_long_gap = false;
byte previous_LDR_state = LOW;
loop() {
if the ldr was previoulsy low and it is now high
handle_a_low(millis()-startMs);
startMs = millis();
previous_LDR_state = HIGH;
else
if the ldr was previoulsy high and it is now low
handle_a_high(millis()-startMs);
startMs = millis();
previous_LDR_state = LOW;
we_might_need_to_handle_a_long_gap = true;
else
if the ldr has been low for some time (unit*10, say) and we_might_need_to_handle_a_long_gap
handle_a_low(millis()-startMs);
we_might_need_to_handle_a_long_gap = false;
end
}
void handle_a_low(uint32_t ms) {
if(ms<unit/2) {
looks like noise, do nothing
}
else if(ms < unit * 2) {
handle_a_gap_between_dotdash()
}
else if (ms < gap * 4) {
handle_a_gap_between_letters();
}
else {
handle_a_gap_between_words();
}
}
void handle_a_high(uint32_t ms) {
if(ms<unit/2) {
looks like noise, do nothing
}
else if(ms < unit * 2) {
handle_a_dot()
}
else if(ms < unit * 5) {
handle_a_dash()
}
else {
looks like the sender is stuck, do nothing
}
}
void handle a dot() {
add a dot to the buffer, making sure not to overwrite the end of the buffer
}
void handle a dash() {
add a dash to the buffer, making sure not to overwrite the end of the buffer
}
void handle a gap between letters() {
check the buffer aginast letters we recognize, print out the letter
clear the buffer
}
void handle a gap between words() {
handle a gap between letters(); // take care of the pending letter
print out a space
}