NRF24L01+ Getting Started Acknowledge Failed

Question

I have followed numerous guides and tutorials for getting the NRF24L01+ modules working with an Arduino Uno. I have swapped to a genuine Arduino and tried 4 different NRF modules. All without luck.

I am trying to get the most basic example from Simple nRF24L01+ 2.4GHz transceiver demo to work.

Hardware Connections: Hardware Connections

Simple TX Test Code:

// SimpleTx - the master or the transmitter
#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
#define CE_PIN 9
#define CSN_PIN 10
const byte slaveAddress[5] = {'R','x','A','A','A'};
RF24 radio(CE_PIN, CSN_PIN); // Create a Radio
char dataToSend[10] = "Message 0";
char txNum = '0';
unsigned long currentMillis;
unsigned long prevMillis;
unsigned long txIntervalMillis = 1000; // send once per second
void setup() {
 Serial.begin(9600);
 Serial.println("SimpleTx Starting");
 radio.begin();
 radio.setDataRate( RF24_250KBPS );
 radio.setRetries(3,5); // delay, count
 radio.openWritingPipe(slaveAddress);
}
//====================
void loop() {
 currentMillis = millis();
 if (currentMillis - prevMillis >= txIntervalMillis) {
 send();
 prevMillis = millis();
 }
}
//====================
void send() {
 bool rslt;
 radio.stopListening();
 rslt = radio.write( &dataToSend, sizeof(dataToSend) );
 // Always use sizeof() as it gives the size as the number of bytes.
 // For example if dataToSend was an int sizeof() would correctly return 2
 Serial.print("Data Sent ");
 Serial.print(dataToSend);
 if (rslt) {
 Serial.println(" Acknowledge received");
 updateMessage();
 }
 else {
 Serial.println(" Tx failed");
 }
}
//================
void updateMessage() {
 // so you can see that new data is being sent
 txNum += 1;
 if (txNum > '9') {
 txNum = '0';
 }
 dataToSend[8] = txNum;
}

Serial monitor:

enter image description here

Using radio.printDetails( ); returns:

enter image description here

Please let me know what I'm missing.

• Avamander: Can you please upload the unmodified PingPair example and see if that works?
• Gerben: Where is the code for the receiving side? If there is no receiver, the sender won't get an ACK packet back, and you get the TX failed error message.
• AnT stands with Russia: What is this: uint8_t slaveAddress[5] = {0xF0F0F0F0A1LL, 0XF0F0F0F0B1LL, 0XF0F0F0F0C1LL, 0XF0F0F0F0D1LL, 0XF0F0F0F0E1LL};? How do you expect such large values to fit into uint8_t??? The compiler will interpret this as uint8_t slaveAddress[5] = {0xA1, 0xB1, 0xC1, 0xD1, 0xE1};. Is this what you wanted? I'd guess not. Also, take a look here github.com/nRF24/RF24/blob/master/RF24.h#L246 how the address is supposed to be formed.
• Jak: @AnT I was trying the same as 1 of the answers here: arduino.stackexchange.com/questions/65249/… before you commented there as well. Thank you, have updated the question and code.
• Jak: Thank you all so much. Not sure why I was expecting the radio.write function to return True without a receiving end. It's working.

Answer 1

The Arduinos 3V3 does not privide enough current. To eliminate this as a source of your problem you can use a ceramic capacitor of 100μF across VCC and GND pins of the nRF24L01+ module or buy a 5V to 3V3 step down converter specially made for nRF24L01.