One shift delay in receiving the response messages when using two nRF24L01 to communicate with each other

Question

When I send "a" from the Serial Monitor of the slave, on the master slave window it will show "car1_place_2_go = a" then it should show on the slave Serial Monitor "a" but it doesn't show up in the slave serial window until I send another new characters. So there is a 1 delay shift in the messages showed on the slave Serial Monitor.

Master:

#include <SPI.h>
#include <SoftwareSerial.h>
#include <nRF24L01.h>
#include <RF24.h>

RF24 radio(7, 8); // CE, CSN
const byte addresses[][6] = {"00001", "00002"};

char car1_place_2_go;
char car2_place_2_go;
char temp_place = 0 ;


void setup()
{
  Serial.begin(9600);
  radio.begin();
  radio.openWritingPipe(addresses[1]); // mastr
  radio.openReadingPipe(1, addresses[0]); // carwl

  radio.setPALevel(RF24_PA_MIN);
}


void loop()
{
  delay(5);
  radio.startListening();

  if (radio.available())
  {
    radio.read(&car1_place_2_go, sizeof(car1_place_2_go));
    Serial.print("car1_place_2_go = ");
    Serial.println(car1_place_2_go);

    delay(5);
    radio.stopListening();

    radio.write(&car1_place_2_go, sizeof(car1_place_2_go));
  }
}

Slave:

#include <SPI.h>
#include <SoftwareSerial.h>
#include <nRF24L01.h>
#include <RF24.h>

RF24 radio(7, 8); // CE, CSN
const byte addresses[][6] = {"00001", "00002"};

char car1_place_2_go;
char car2_place_2_go;


void setup() {
  Serial.begin(9600);
  radio.begin();
  radio.openWritingPipe(addresses[0]); // 00003
  radio.openReadingPipe(1, addresses[1]); // 00002

  radio.setPALevel(RF24_PA_MIN);
}


void loop()
{
  if (Serial.available() > 0)
  {
    car2_place_2_go = Serial.read();

    delay(5);
    radio.stopListening();

    radio.write(&car2_place_2_go, sizeof(car2_place_2_go));

    radio.startListening();

    if ( radio.available())
    {
      char text[32] = "";
      radio.read(&text, sizeof(text));
      Serial.println(text);
    }
  }
}

Library I use: https://github.com/nRF24/RF24

Answer 1

i found the problem is that the receiver in the slave doesn't see what send to it until the next loop and that mean it need a delay so it can see what transmit to it so i add this while loop in the slave so the slave doesn't exit the "void loop" function until it get the message from the master

slave

 radio.startListening();

    while(! radio.available())
    {

    }
    if ( radio.available()) 
    {
        char text[32] = "";
        radio.read(&text, sizeof(text));
        Serial.println(text);
     }