manualAcknowledgements.cpp

/*
 * See documentation at https://nRF24.github.io/RF24
 * See License information at root directory of this library
 * Author: Brendan Doherty (2bndy5)
 */

/**
 * A simple example of sending data from 1 nRF24L01 transceiver to another
 * with manually transmitted (non-automatic) Acknowledgement (ACK) payloads.
 * This example still uses ACK packets, but they have no payloads. Instead the
 * acknowledging response is sent with `write()`. This tactic allows for more
 * updated acknowledgement payload data, where actual ACK payloads' data are
 * outdated by 1 transmission because they have to loaded before receiving a
 * transmission.
 *
 * This example was written to be used on 2 devices acting as "nodes".
 * Use `ctrl+c` to quit at any time.
 */
#include <ctime>       // time()
#include <iostream>    // cin, cout, endl
#include <string>      // string, getline()
#include <time.h>      // CLOCK_MONOTONIC_RAW, timespec, clock_gettime()
#include <RF24/RF24.h> // RF24, RF24_PA_LOW, delay()

using namespace std;

/****************** Linux ***********************/
// Radio CE Pin, CSN Pin, SPI Speed
// CE Pin uses GPIO number with BCM and SPIDEV drivers, other platforms use their own pin numbering
// CS Pin addresses the SPI bus number at /dev/spidev<a>.<b>
// ie: RF24 radio(<ce_pin>, <a>*10+<b>); spidev1.0 is 10, spidev1.1 is 11 etc..
#define CSN_PIN 0
#ifdef MRAA
    #define CE_PIN 15 // GPIO22
#elif defined(RF24_WIRINGPI)
    #define CE_PIN 3 // GPIO22
#else
    #define CE_PIN 22
#endif
// Generic:
RF24 radio(CE_PIN, CSN_PIN);
/****************** Linux (BBB,x86,etc) ***********************/
// See http://nRF24.github.io/RF24/pages.html for more information on usage
// See https://github.com/eclipse/mraa/ for more information on MRAA
// See https://www.kernel.org/doc/Documentation/spi/spidev for more information on SPIDEV

// For this example, we'll be using a payload containing
// a string & an integer number that will be incremented
// on every successful transmission.
// Make a data structure to store the entire payload of different datatypes
struct PayloadStruct
{
    char message[7]; // only using 6 characters for TX & RX payloads
    uint8_t counter;
};
PayloadStruct payload;

void setRole(); // prototype to set the node's role
void master();  // prototype of the TX node's behavior
void slave();   // prototype of the RX node's behavior

// custom defined timer for evaluating transmission time in microseconds
struct timespec startTimer, endTimer;
uint32_t getMicros(); // prototype to get elapsed time in microseconds

int main(int argc, char** argv)
{

    // perform hardware check
    if (!radio.begin()) {
        cout << "radio hardware is not responding!!" << endl;
        return 0; // quit now
    }

    // append a NULL terminating 0 for printing as a c-string
    payload.message[6] = 0;

    // Let these addresses be used for the pair of nodes used in this example
    uint8_t address[2][6] = {"1Node", "2Node"};
    //             the TX address^ ,  ^the RX address
    // It is very helpful to think of an address as a path instead of as
    // an identifying device destination

    // to use different addresses on a pair of radios, we need a variable to
    // uniquely identify which address this radio will use to transmit
    bool radioNumber = 1; // 0 uses address[0] to transmit, 1 uses address[1] to transmit

    // print example's name
    cout << argv[0] << endl;

    // Set the radioNumber via the terminal on startup
    cout << "Which radio is this? Enter '0' or '1'. Defaults to '0' ";
    string input;
    getline(cin, input);
    radioNumber = input.length() > 0 && (uint8_t)input[0] == 49;

    // Set the PA Level low to try preventing power supply related problems
    // because these examples are likely run with nodes in close proximity to
    // each other.
    radio.setPALevel(RF24_PA_LOW); // RF24_PA_MAX is default.

    // save on transmission time by setting the radio to only transmit the
    // number of bytes we need to transmit a float
    radio.setPayloadSize(sizeof(payload)); // char[7] & uint8_t datatypes occupy 8 bytes

    // set the TX address of the RX node into the TX pipe
    radio.openWritingPipe(address[radioNumber]); // always uses pipe 0

    // set the RX address of the TX node into a RX pipe
    radio.openReadingPipe(1, address[!radioNumber]); // using pipe 1

    // For debugging info
    // radio.printDetails();       // (smaller) function that prints raw register values
    // radio.printPrettyDetails(); // (larger) function that prints human readable data

    // ready to execute program now
    setRole(); // calls master() or slave() based on user input
    return 0;
} // main

/**
 * set this node's role from stdin stream.
 * this only considers the first char as input.
 */
void setRole()
{
    string input = "";
    while (!input.length()) {
        cout << "*** PRESS 'T' to begin transmitting to the other node\n";
        cout << "*** PRESS 'R' to begin receiving from the other node\n";
        cout << "*** PRESS 'Q' to exit" << endl;
        getline(cin, input);
        if (input.length() >= 1) {
            if (input[0] == 'T' || input[0] == 't')
                master();
            else if (input[0] == 'R' || input[0] == 'r')
                slave();
            else if (input[0] == 'Q' || input[0] == 'q')
                break;
            else
                cout << input[0] << " is an invalid input. Please try again." << endl;
        }
        input = ""; // stay in the while loop
    }               // while
} // setRole()

/**
 * make this node act as the transmitter
 */
void master()
{

    memcpy(payload.message, "Hello ", 6); // set the outgoing message
    radio.stopListening();                // put in TX mode

    unsigned int failures = 0; // keep track of failures
    while (failures < 6) {
        clock_gettime(CLOCK_MONOTONIC_RAW, &startTimer);      // start the timer
        bool report = radio.write(&payload, sizeof(payload)); // transmit & save the report

        if (report) {
            // transmission successful; wait for response and print results

            radio.startListening();                 // put in RX mode
            unsigned long start_timeout = millis(); // timer to detect no response
            while (!radio.available()) {            // wait for response
                if (millis() - start_timeout > 200) // only wait 200 ms
                    break;
            }
            unsigned long elapsedTime = getMicros(); // end the timer
            radio.stopListening();                   // put back in TX mode

            // print summary of transactions
            uint8_t pipe;
            cout << "Transmission successful! ";
            if (radio.available(&pipe)) {               // is there a payload received? grab the pipe number that received it
                uint8_t bytes = radio.getPayloadSize(); // grab the incoming payload size
                cout << "Round trip delay = ";
                cout << elapsedTime;                      // print the timer result
                cout << " us. Sent: " << payload.message; // print outgoing message
                cout << (unsigned int)payload.counter;    // print outgoing counter
                PayloadStruct received;
                radio.read(&received, sizeof(received));     // get incoming payload
                cout << " Received " << (unsigned int)bytes; // print incoming payload size
                cout << " on pipe " << (unsigned int)pipe;   // print RX pipe number
                cout << ": " << received.message;            // print the incoming message
                cout << (unsigned int)received.counter;      // print the incoming counter
                cout << endl;
                payload.counter = received.counter; // save incoming counter for next outgoing counter
            }
            else {
                cout << "Received no response." << endl; // no response received
            }
        }
        else {
            cout << "Transmission failed or timed out"; // payload was not delivered
            cout << endl;
            failures++; // increment failure counter
        }               // report

        // to make this example readable in the terminal
        delay(1000); // slow transmissions down by 1 second
    }                // while

    cout << failures << " failures detected. Leaving TX role." << endl;
} // master

/**
 * make this node act as the receiver
 */
void slave()
{
    memcpy(payload.message, "World ", 6); // set the response message
    radio.startListening();               // put in RX mode

    time_t startTimer = time(nullptr);       // start a timer
    while (time(nullptr) - startTimer < 6) { // use 6 second timeout
        uint8_t pipe;
        if (radio.available(&pipe)) {               // is there a payload? get the pipe number that received it
            uint8_t bytes = radio.getPayloadSize(); // get size of incoming payload
            PayloadStruct received;
            radio.read(&received, sizeof(received)); // get incoming payload
            payload.counter = received.counter + 1;  // increment payload for response

            // transmit response & save result to `report`
            radio.stopListening();                      // put in TX mode
            radio.writeFast(&payload, sizeof(payload)); // load response into TX FIFO
            bool report = radio.txStandBy(150);         // keep retrying for 150 ms
            radio.startListening();                     // put back in RX mode

            // print summary of transactions
            cout << "Received " << (unsigned int)bytes; // print the size of the payload
            cout << " bytes on pipe ";
            cout << (unsigned int)pipe;             // print the pipe number
            cout << ": " << received.message;       // print incoming message
            cout << (unsigned int)received.counter; // print incoming counter

            if (report) {
                cout << " Sent: " << payload.message;  // print outgoing message
                cout << (unsigned int)payload.counter; // print outgoing counter
                cout << endl;
            }
            else {
                cout << " Response failed to send." << endl; // failed to send response
            }
            startTimer = time(nullptr); // reset timer
        }                               // available
    }                                   // while

    cout << "Nothing received in 6 seconds. Leaving RX role." << endl;
    radio.stopListening(); // recommended idle mode is TX mode
} // slave

/**
 * Calculate the elapsed time in microseconds
 */
uint32_t getMicros()
{
    // this function assumes that the timer was started using
    // `clock_gettime(CLOCK_MONOTONIC_RAW, &startTimer);`

    clock_gettime(CLOCK_MONOTONIC_RAW, &endTimer);
    uint32_t seconds = endTimer.tv_sec - startTimer.tv_sec;
    uint32_t useconds = (endTimer.tv_nsec - startTimer.tv_nsec) / 1000;

    return ((seconds)*1000 + useconds) + 0.5;
}