nRF24L01+: Not Receiving ACK at PTX

[ab]

Hi, I am interfacing a TI TM4C123 microcontroller to the AddiCore nRF24L01+ Transceiver Module. I can consistently transmit and receive data with the microcontroller/nRF24L01+ modules, however the PTX does not receive the ACK from PRX. Using UARTs connected to each of the PTX and PRX, I can see the PRX receives the packet correctly but I don't get the ACK at the PTX. I have included the code to set-up the nRF24L01+ in PTX or RTX modes. Any help would be appreciated.

// Switch has been pressed.
// Initialize Wireless Interface (nRF24L01+)
// ************************************************************
// Transmitter
// ************************************************************
if (PF_In & 0x10) {
	// Switch 2 has been pressed to configure as transmitter.
	// Set up Nordic nRF24L01+ in transmit mode
    // Initialize the 24L01+ to the debug configuration as TX, x data byte, and auto-ack enabled
	nrf24l01_initialize_debug(false, NUMBYTES_PERPACKET, true);
		
    GPIO_PORTF_DATA_R |= 0x04;       // turn on blue LED
		
	// Display message by sending to UART
	UART_OutString((unsigned char*)"Transmit Mode Selected *");
	UART_sendCRLF( );
		
	// ***********************************************************************
	// ***********************************************************************
	// Transmitter Loop
	while(1) {
        UART_sendCRLF( );
		UART_sendCRLF( );
		UART_OutString((unsigned char*)"----------------------------  *");
		UART_sendCRLF( );
        UART_OutString((unsigned char*)"Transmission Cycle =  *");   // tx_cycle
		UART_OutChar(tx_cycle);
		UART_sendCRLF( );
		tx_cycle++;

        // Wait until either switch is pressed
        PF_In = GPIO_PORTF_DATA_R&0x11;       // read Sw1 & SW2
        while (PF_In == 0x11) { 
            PF_In = GPIO_PORTF_DATA_R&0x11;   // Check SW1 and SW2
        };
			
		// Load data array
		for (indx=0; indx<NUMBYTES_PERPACKET; indx++) {
			operator_input[indx] = tx_cycle + indx;
		}
			
		UART_OutString((unsigned char*)"Assigned input:  *");
		UART_OutChar(operator_input[0]);
		UART_sendCRLF( );
			
		nrf24l01_write_tx_payload(operator_input, pack_length, true); // write data to TX Fifo
			
		// wait until the nRF24L01+ IRQ pin is active (either RX_DR or MAX_RT flags active)
        while(!nrf24l01_irq_pin_active()) {};

		// Read status register
		nrf24l01_read_register(nrf24l01_STATUS, &status_reg, 1);
		status_reg &= nrf24l01_CONFIG_MASK_RX_DR;    // mask all bits but RX_DR
				
		if(status_reg == nrf24l01_CONFIG_MASK_RX_DR) {
            nrf24l01_irq_clear_all(); //clear all interrupts in the 24L01

			nrf24l01_read_rx_payload(&data_transmit, pack_length); //get the payload into data
                
            nrf24l01_irq_clear_all(); //clear interrupts again
			UART_sendCRLF( );
			UART_OutString((unsigned char*)"Transmit Done. *");
			UART_sendCRLF( );
			UART_OutString((unsigned char*)"Ack Data Received:  *");
			UART_OutChar(data_transmit);
			UART_sendCRLF( );
					
			delay_us(130);  //wait for receiver to come from standby to RX
			
			delay_us(200000); // debounce switches
			GPIO_PORTF_DATA_R ^= 0x04;       // toggle blue LED
        }
		// Maximum number of retries has been reached.
        else {
            nrf24l01_flush_tx(); //get the unsent character out of the TX FIFO
            nrf24l01_irq_clear_all(); //clear all interrupts
			UART_OutString((unsigned char*)"Max num of retries reached. Ack was not received. *");
			UART_sendCRLF( );
			delay_us(200000); // debounce switches
			GPIO_PORTF_DATA_R ^= 0x04;       // toggle blue LED
        }
	}	
}
			
// ***********************************************************************
// ***********************************************************************
// Receiver
else {
	// Switch 1 has been pressed to configure as receiver.
	// Set up Nordic nRF24L01+ in receive mode
    // Initialize the 24L01+ to the debug configuration as RX, 1 data byte, and auto-ack enabled
	nrf24l01_initialize_debug(true, NUMBYTES_PERPACKET, true);
	
	GPIO_PORTF_DATA_R |= 0x08;       // turn on green LED
	
	UART_OutString((unsigned char*)"Receive Mode Selected *");
	UART_sendCRLF( );
	
    //main RX program loop
    while(1) {			
		UART_OutString((unsigned char*)"Waiting for Receiver command. *");
		UART_sendCRLF( );
		recd_cmd = 0x00;  // clear received command
			
		// clear all interrupts and flush both TX and RX Fifos
		nrf24l01_clear_flush();    // ab July 28, 2014
			
		//wait until a packet has been received; IRQ pin will go low
		while(!nrf24l01_irq_pin_active()) {};
		delay_us(230);   //wait for the other 24L01 to come from standby to RX
        
		// Read one extra byte from the RX Fifo.  The first is the Status Register,
		// the rest of the bytes are the received data.
		nrf24l01_read_rx_payload(buf_array, NUMBYTES_PERPACKET+1); //read the packet into data
			
		UART_OutString((unsigned char*)"Status Register value: *");
		UART_OutChar(buf_array[0]);     // send received data to UART
		UART_sendCRLF( );
			
		// Now send data received to display
		for (indx=0; indx < NUMBYTES_PERPACKET; indx++) {
			UART_OutString((unsigned char*)"Received Data: *");
			UART_OutChar(buf_array[indx+1]);     // send received data to UART
			UART_sendCRLF( );
		}

		nrf24l01_irq_clear_all(); //clear interrupts again
		GPIO_PORTF_DATA_R ^= 0x08;       // toggle green LED
	}
}

}

[Håkon Alseth]

It would be great to have a look at the init of the L01+. Could you attach this?

One of the "normal" issues when the PRX receives the payload w/o issues, and the PTX does not receive the ACK is that the PTXs pipes are not correctly set up. On the PTX you need to set TX_PIPE equal to PIPE0 in order for auto-ACKing to work properly.

cheers, Håkon