
/*
  Getting Started example sketch for nRF24L01+ radios
  This is a very basic example of how to send data from one node to another
  but modified to include failure handling.

  The nrf24l01+ radios are fairly reliable devices, but on breadboards etc, with inconsistent wiring, failures may
  occur randomly after many hours to days or weeks. This sketch demonstrates how to handle the various failures and
  keep the radio operational.

  The three main failure modes of the radio include:
  Writing to radio: Radio unresponsive - Fixed internally by adding a timeout to the internal write functions in RF24 (failure handling)
  Reading from radio: Available returns true always - Fixed by adding a timeout to available functions by the user. This is implemented internally in  RF24Network.
  Radio configuration settings are lost - Fixed by monitoring a value that is different from the default, and re-configuring the radio if this setting reverts to the default.

  The printDetails output should appear as follows for radio #0:

  STATUS         = 0x0e RX_DR=0 TX_DS=0 MAX_RT=0 RX_P_NO=7 TX_FULL=0
  RX_ADDR_P0-1   = 0x65646f4e31 0x65646f4e32
  RX_ADDR_P2-5   = 0xc3 0xc4 0xc5 0xc6
  TX_ADDR        = 0x65646f4e31
  RX_PW_P0-6     = 0x20 0x20 0x00 0x00 0x00 0x00
  EN_AA          = 0x3f
  EN_RXADDR      = 0x02
  RF_CH          = 0x4c
  RF_SETUP       = 0x03
  CONFIG         = 0x0f
  DYNPD/FEATURE  = 0x00 0x00
  Data Rate      = 1MBPS
  Model          = nRF24L01+
  CRC Length     = 16 bits
  PA Power       = PA_LOW

  Users can use this sketch to troubleshoot radio module wiring etc. as it makes the radios hot-swappable

  Updated: 2019 by TMRh20
*/

#include <SPI.h>
#include "RF24.h"
#include "printf.h"

/****************** User Config ***************************/
/***      Set this radio as radio number 0 or 1         ***/
bool radioNumber = 0;

/* Hardware configuration: Set up nRF24L01 radio on SPI bus plus pins 7 & 8 */
RF24 radio(7, 8);
/**********************************************************/

byte addresses[][6] = { "1Node", "2Node" };

// Used to control whether this node is sending or receiving
bool role = 0;


/**********************************************************/
//Function to configure the radio
void configureRadio() {

  radio.begin();

  // Set the PA Level low to prevent power supply related issues since this is a
  // getting_started sketch, and the likelihood of close proximity of the devices. RF24_PA_MAX is default.
  radio.setPALevel(RF24_PA_LOW);

  // Open a writing and reading pipe on each radio, with opposite addresses
  if (radioNumber) {
    radio.openWritingPipe(addresses[1]);
    radio.openReadingPipe(1, addresses[0]);
  } else {
    radio.openWritingPipe(addresses[0]);
    radio.openReadingPipe(1, addresses[1]);
  }

  // Start the radio listening for data
  radio.startListening();
  radio.printDetails();
}


/**********************************************************/

void setup() {
  Serial.begin(115200);
  Serial.println(F("RF24/examples/GettingStarted"));
  Serial.println(F("*** PRESS 'T' to begin transmitting to the other node"));

  printf_begin();

  configureRadio();
}

uint32_t configTimer = millis();

void loop() {

  if (radio.failureDetected) {
    radio.failureDetected = false;
    delay(250);
    Serial.println("Radio failure detected, restarting radio");
    configureRadio();
  }
  // Every 5 seconds, verify the configuration of the radio. This can be
  // done using any setting that is different from the radio defaults.
  if (millis() - configTimer > 5000) {
    configTimer = millis();
    if (radio.getDataRate() != RF24_1MBPS) {
      radio.failureDetected = true;
      Serial.print("Radio configuration error detected");
    }
  }


  /****************** Ping Out Role ***************************/

  if (role == 1) {

    radio.stopListening();  // First, stop listening so we can talk.

    Serial.println(F("Now sending"));

    unsigned long start_time = micros();  // Take the time, and send it.  This will block until complete
    if (!radio.write(&start_time, sizeof(unsigned long))) {
      Serial.println(F("failed"));
    }

    radio.startListening();  // Now, continue listening

    unsigned long started_waiting_at = micros();  // Set up a timeout period, get the current microseconds
    bool timeout = false;                         // Set up a variable to indicate if a response was received or not

    while (!radio.available())  // While nothing is received
    {
      if (micros() - started_waiting_at > 200000)  // If waited longer than 200ms, indicate timeout and exit while loop
      {
        timeout = true;
        break;
      }
    }

    if (timeout) {
      // Describe the results
      Serial.println(F("Failed, response timed out."));
    } else {
      // Grab the response, compare, and send to debugging spew

      unsigned long got_time;  // Variable for the received timestamp

      // Failure Handling
      uint32_t failTimer = millis();
      while (radio.available())  // If available() always returns true, there is a problem
      {
        if (millis() - failTimer > 250) {
          radio.failureDetected = true;
          Serial.println("Radio available failure detected");
          break;
        }
        radio.read(&got_time, sizeof(unsigned long));
      }
      unsigned long end_time = micros();

      // Spew it
      Serial.print(F("Sent "));
      Serial.print(start_time);
      Serial.print(F(", Got response "));
      Serial.print(got_time);
      Serial.print(F(", Round-trip delay "));
      Serial.print(end_time - start_time);
      Serial.println(F(" microseconds"));
    }

    delay(1000);  // Try again 1s later
  }


  /****************** Pong Back Role ***************************/

  if (role == 0) {
    unsigned long got_time;  // Variable for the received timestamp

    if (radio.available()) {
      uint32_t failTimer = millis();

      while (radio.available())  // While there is data ready
      {
        if (millis() - failTimer > 500) {
          Serial.println("Radio available failure detected");
          radio.failureDetected = true;
          break;
        }
        radio.read(&got_time, sizeof(unsigned long));  // Get the payload
      }

      radio.stopListening();                          // First, stop listening so we can talk
      radio.write(&got_time, sizeof(unsigned long));  // Send the final one back.
      radio.startListening();                         // Now, resume listening so we catch the next packets.
      Serial.print(F("Sent response "));
      Serial.println(got_time);
    }
  }


  /****************** Change Roles via Serial Commands ***************************/

  if (Serial.available()) {
    char c = toupper(Serial.read());
    if (c == 'T' && role == 0) {
      Serial.println(F("*** CHANGING TO TRANSMIT ROLE -- PRESS 'R' TO SWITCH BACK"));
      role = 1;  // Become the primary transmitter (ping out)
    } else if (c == 'R' && role == 1) {
      Serial.println(F("*** CHANGING TO RECEIVE ROLE -- PRESS 'T' TO SWITCH BACK"));
      role = 0;  // Become the primary receiver (pong back)
      radio.startListening();
    }
  }
}  // Loop
