pingpair.pde

This is an example of how to use the RF24 class. Write this sketch to two different nodes, connect the role_pin to ground on one. The ping node sends the current time to the pong node, which responds by sending the value back. The ping node can then see how long the whole cycle took.

/*
 Copyright (C) 2011 J. Coliz <maniacbug@ymail.com>

 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public License
 version 2 as published by the Free Software Foundation.
 */

#include <SPI.h>
#include "nRF24L01.h"
#include "RF24.h"
#include "printf.h"

//
// Hardware configuration
//

// Set up nRF24L01 radio on SPI bus plus pins 9 & 10

RF24 radio(9,10);

// sets the role of this unit in hardware.  Connect to GND to be the 'pong' receiver
// Leave open to be the 'ping' transmitter
const int role_pin = 7;

//
// Topology
//

// Radio pipe addresses for the 2 nodes to communicate.
const uint64_t pipes[2] = { 0xF0F0F0F0E1LL, 0xF0F0F0F0D2LL };

//
// Role management
//
// Set up role.  This sketch uses the same software for all the nodes
// in this system.  Doing so greatly simplifies testing.  The hardware itself specifies
// which node it is.
//
// This is done through the role_pin
//

// The various roles supported by this sketch
typedef enum { role_ping_out = 1, role_pong_back } role_e;

// The debug-friendly names of those roles
const char* role_friendly_name[] = { "invalid", "Ping out", "Pong back"};

// The role of the current running sketch
role_e role;

void setup(void)
{
  //
  // Role
  //

  // set up the role pin
  pinMode(role_pin, INPUT);
  digitalWrite(role_pin,HIGH);
  delay(20); // Just to get a solid reading on the role pin

  // read the address pin, establish our role
  if ( ! digitalRead(role_pin) )
    role = role_ping_out;
  else
    role = role_pong_back;

  //
  // Print preamble
  //

  Serial.begin(57600);
  printf_begin();
  printf("\n\rRF24/examples/pingpair/\n\r");
  printf("ROLE: %s\n\r",role_friendly_name[role]);

  //
  // Setup and configure rf radio
  //

  radio.begin();

  // optionally, increase the delay between retries & # of retries
  radio.setRetries(15,15);

  // optionally, reduce the payload size.  seems to
  // improve reliability
  radio.setPayloadSize(8);

  //
  // Open pipes to other nodes for communication
  //

  // This simple sketch opens two pipes for these two nodes to communicate
  // back and forth.
  // Open 'our' pipe for writing
  // Open the 'other' pipe for reading, in position #1 (we can have up to 5 pipes open for reading)

  if ( role == role_ping_out )
  {
    radio.openWritingPipe(pipes[0]);
    radio.openReadingPipe(1,pipes[1]);
  }
  else
  {
    radio.openWritingPipe(pipes[1]);
    radio.openReadingPipe(1,pipes[0]);
  }

  //
  // Start listening
  //

  radio.startListening();

  //
  // Dump the configuration of the rf unit for debugging
  //

  radio.printDetails();
}

void loop(void)
{
  //
  // Ping out role.  Repeatedly send the current time
  //

  if (role == role_ping_out)
  {
    // First, stop listening so we can talk.
    radio.stopListening();

    // Take the time, and send it.  This will block until complete
    unsigned long time = millis();
    printf("Now sending %lu...",time);
    bool ok = radio.write( &time, sizeof(unsigned long) );
    
    if (ok)
      printf("ok...");
    else
      printf("failed.\n\r");

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

    // Wait here until we get a response, or timeout (250ms)
    unsigned long started_waiting_at = millis();
    bool timeout = false;
    while ( ! radio.available() && ! timeout )
      if (millis() - started_waiting_at > 200 )
        timeout = true;

    // Describe the results
    if ( timeout )
    {
      printf("Failed, response timed out.\n\r");
    }
    else
    {
      // Grab the response, compare, and send to debugging spew
      unsigned long got_time;
      radio.read( &got_time, sizeof(unsigned long) );

      // Spew it
      printf("Got response %lu, round-trip delay: %lu\n\r",got_time,millis()-got_time);
    }

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

  //
  // Pong back role.  Receive each packet, dump it out, and send it back
  //

  if ( role == role_pong_back )
  {
    // if there is data ready
    if ( radio.available() )
    {
      // Dump the payloads until we've gotten everything
      unsigned long got_time;
      bool done = false;
      while (!done)
      {
        // Fetch the payload, and see if this was the last one.
        done = radio.read( &got_time, sizeof(unsigned long) );

        // Spew it
        printf("Got payload %lu...",got_time);

        // Delay just a little bit to let the other unit
        // make the transition to receiver
        delay(20);
      }

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

      // Send the final one back.
      radio.write( &got_time, sizeof(unsigned long) );
      printf("Sent response.\n\r");

      // Now, resume listening so we catch the next packets.
      radio.startListening();
    }
  }
}
// vim:cin:ai:sts=2 sw=2 ft=cpp