nRF24L01+ receiver problems

[jeremyc123]

Hello,

I am currently using a custom-built board designed to the nRF24L01+ specification and using the same exact circuit provided in their datasheet. It is connected to my STM32F103 through SPI. I am currently using this library to test out this board: https://github.com/elmot/nrf24l01-lib/tree/master

The board is able to successfully verify that it is connected to the NRF chip using the nRF24_Check() function. Furthermore, the nRF is returning back that a packet (without AA) has been sent successfully and subsequently clears the TX FIFO. On my receiver device, the RX FIFO does not get populated nor any interrupts triggered by the nRF which leads me to the assumption that there is a problem somewhere with the wireless transmission of the packet. If I were to enable AA, and also put my receiver device on the ESB RX example, then the nRF would return that the maximum number of transmissions has occurred.

It is my first time attempting to debug a wireless device that I have made so I would appreciate any help or suggestions on where to look and what to verify. 

[Richard Lowe]

I would have to see the code. I'm very familiar with that radio and have written my own library.  It seems to be spi bus specific. Post your spi bus initialization code and bus speed. 

I'd look at spi bus settings first, then addressing. Then line pull ups on the 2 select gpio lines.

[Richard Lowe]

You have 2 lines on the NRF24L01, CSN and CE.

/*Configure GPIO pin Output Level */
// Start both HIGH
HAL_GPIO_WritePin(NRF_CE_GPIO_Port, NRF_CE_Pin, GPIO_PIN_SET); 
HAL_GPIO_WritePin(NRF_CSN_GPIO_Port, NRF_CSN_Pin, GPIO_PIN_SET);

/*Configure GPIO pin : NRF_CE_Pin */
GPIO_InitStruct.Pin = NRF_CE_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(NRF_CE_GPIO_Port, &GPIO_InitStruct);

/*Configure GPIO pin : NRF_CSN_Pin */
GPIO_InitStruct.Pin = NRF_CSN_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(NRF_CSN_GPIO_Port, &GPIO_InitStruct);

And make sure your SPI bus is no faster than 5MHz. Anything faster will result in unpredictable behavior.

[jeremyc123]

SPI Init

hspi2.Instance = SPI2;
  hspi2.Init.Mode = SPI_MODE_MASTER;
  hspi2.Init.Direction = SPI_DIRECTION_2LINES;
  hspi2.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi2.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi2.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi2.Init.NSS = SPI_NSS_SOFT;
  hspi2.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_16;
  hspi2.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi2.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi2.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi2.Init.CRCPolynomial = 10;
  if (HAL_SPI_Init(&hspi2) != HAL_OK)
  {
    Error_Handler();
  }

GPIO Init

/Configure GPIO pin : NRF_CE_Pin/
  GPIO_InitStruct.Pin = NRF_CE_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
  HAL_GPIO_Init(NRF_CE_GPIO_Port, &GPIO_InitStruct);

  /Configure GPIO pin : NRF_CS_Pin/
  GPIO_InitStruct.Pin = NRF_CS_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
  HAL_GPIO_Init(NRF_CS_GPIO_Port, &GPIO_InitStruct);

[Richard Lowe]

I don't have any familiarity with that library, and can't see why it wouldn't work. I did notice one thing. According to the datasheet of the NRF24L01, when sending a packet, you need to "pulse" the CE line for at least 10us to clock in the transmission. I didn't see that happening in the library.

/**
 * Pulses the CE to nRF24L01 for at least 10 us
 */
#define CE_PULSE() do { \
  uint8_t count; \
  count = 20; \
  CE_HIGH();  \
  while(count--) \
    ; \
  CE_LOW();  \
  } while(0)

This is in the Nordic library for that radio:

void radio_send_packet( uint8_t *packet, uint8_t length )
{
	hal_nrf_write_tx_pload( packet, length );    // load message into radio

	CE_PULSE( );                                 // send packet

	radio_set_status( RF_BUSY );                 // trans. in progress; RF_BUSY
}

And this is in your library:

void nRF24_WriteAckPayload(nRF24_RXResult pipe, char *payload, uint8_t length) {
	nRF24_CSN_L();
	nRF24_LL_RW(nRF24_CMD_W_ACK_PAYLOAD | pipe);
	while (length--) {
		nRF24_LL_RW((uint8_t) *payload++);
	}
	nRF24_CSN_H();
}

Is this a library you have tested before?

[AScha.3]

>then the nRF would return that the maximum number of transmissions has occurred.

iirr maybe the nrf24 is right - depending on mode each transmission gets acknowledge back , if not, it retries transmission up to max.number. So this just shows: receiver got no valid packet.

did you set the packet "ID" on both ?

const uint64_t pipe = 0xAFFEAFFE1111; // Needs to be the same for communicating between 2 NRF24L01

[jeremyc123]

I switched to a completely new example, no cigar. I realized in my circuit that I wired the IREF incorrectly to 3.3v instead of to ground. I removed the resistor and let IREF float and there was no change. I then wired IREF properly over a 22k to GND and still nothing on both devices. I tried hooking an oscilloscope to the output of the antenna to see if I could see at least some signal, however, it appeared as if it was being pulled to ground. I verified that the circuit has no problem reading and writing registers to the NRF, and that there is active SPI communication. On the receiver, I verified that the CS and CE pins were both low while it was receiving. I am running out of things to test without trying to get a spectrum analyzer to see if anything is actually being transmitted.

[AScha.3]

i used mini module , about 1 $ ->

https://de.aliexpress.com/item/32914543301.html

just connect it and it was working fine .

maybe you should start with 2 of them, to check your software etc. , then go for using your onboard design.

[jeremyc123]

Definitely should have started there. I was able to get my hands on a spectrum analyzer and I confirmed that there was nothing being transmitted at all. I'll go ahead and try Richard's solution and see if I get any luck. I'll also mess with the STM's clock speed and see if that makes any changes. 

[jeremyc123]

Not a library I have tested before, I tried with multiple libraries now and I am still not seeing any positive results. I tried lowering the clock speed and pulsing the CE but still no results.