I have a beginner's problem.... I have got 2 x NRF24L01+ devices, they are communicating with each other great, and i can talk with the nrf's via SPI. The problem is i want to display, on the serial monitor, the number of retransmitted packets (ARC_CNT) and the number of lost packets (PLOS_CNT), which are both in the "observe_tx" register on the nrf. I am using the "Getting Started" example from RF24 1.3.1, with Arduino 1.84, with a few more bits added, and it all works great apart from getting it to show PLOS_CNT & ARC_CNT! I have tried: printf_P(PSTR("OBSERVE_TX=%02x: PLOS_CNT=%x ARC_CNT=%x\r\n")); but this does not give the correct result. As you have probably guessed i know nothing about C or C++ :) There must be a simple way of showing the 2 numbers ? The code i am using is : /* Getting Started example sketch for nRF24L01+ radios This is a very basic example of how to send data from one node to another Updated: Dec 2014 by TMRh20 */ #include <SPI.h> #include "RF24.h" #include <printf.h> // Required for "radio.printDetails();" /****************** 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; void setup() { //pinMode(53,OUTPUT); //may not be required after all Serial.begin(115200); printf_begin(); //required for "radio.printDetails();" to work Serial.println(F("RF24/examples/GettingStarted")); Serial.println(F("*** PRESS 'T' to begin transmitting to the other node")); 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); // _MIN, _LOW, _HIGH, _MAX radio.setDataRate(RF24_250KBPS); //250KBPS, _1MBPS, _2MBPS Lowest rate gives longest range. radio.setChannel(108); // 0 - 124 (2.4GHz - 2.524GHz) Usually above 100 best. USA 70 - 80 best. //radio.enableDynamicPayloads(); radio.setRetries(15, 15); // set retry delay and no of retries. delay between retries, 0=250uS, 15 = 4000uS radio.setCRCLength(RF24_CRC_16); // 8 or 16 bit crc //radio.setAutoAck(1); Ensure autoACK is enabled //radio.enableAckPayload(); Allow optional ack payloads //radio.setPayloadSize(1); Here we are sending 1-byte payloads to test the call-response speed //radio.openWritingPipe(pipes[1]); Both radios listen on the same pipes by default, and switch when writing //radio.openReadingPipe(1,pipes[0]); radio.printDetails(); // Serial.print(radio.getChannel()); //Serial.print(radio.getxxxx()); prints to the serial port the value your are getting from the nRF24l01 radio.setAutoAck(1); //radio.powerDown(); //radio.powerUp(); //radio.setAddressWidth(5); // set AW to 3, 4 or 5. /* getChannel(); getPayloadSize(); getDynamicpayloadSize(); getPALevel(); getDataRate(); getCRCLength(); */ // 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(); } void loop() { /****************** 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 boolean 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.")); printf_P(PSTR("OBSERVE_TX=%02x: PLOS_CNT=%x ARC_CNT=%x\r\n")); } else { unsigned long got_time; // Grab the response, compare, and send to debugging spew 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")); } // Try again 1s later delay(1000); } /****************** Pong Back Role ***************************/ if ( role == 0 ) { unsigned long got_time; if ( radio.available()) { // Variable for the received timestamp while (radio.available()) { // While there is data ready 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