Access custom data (actual payload) inside ESB payload

[astomi]

Hi,

I am trying to modify ACK handling in ESB(nrf_esb.c, inside on_radio_disabled_rx()) but confused about accessing real payload data (PRX example, SDK17)

1.  

   static  uint8_t  m_rx_payload_buffer[NRF_ESB_MAX_PAYLOAD_LENGTH + 2]

    is used for receive by setting 

   NRF_RADIO->PACKETPTR        = (uint32_t)m_rx_payload_buffer;

    
2. It should hold total ESB payload defined as 

   typedef struct
   {
       uint8_t length;                                 //!< Length of the packet (maximum value is @ref NRF_ESB_MAX_PAYLOAD_LENGTH).
       uint8_t pipe;                                   //!< Pipe used for this payload.
       int8_t  rssi;                                   //!< RSSI for the received packet.
       uint8_t noack;                                  //!< Flag indicating that this packet will not be acknowledgement. Flag is ignored when selective auto ack is enabled.
       uint8_t pid;                                    //!< PID assigned during communication.
       uint8_t data[NRF_ESB_MAX_PAYLOAD_LENGTH];       //!< The payload data.
   } nrf_esb_payload_t;
   

    
3. I guess that would make first byte of data as m_rx_payload_buffer[5]?
4. However, I can see stuff like this: 

           memcpy(m_rx_fifo.p_payload[m_rx_fifo.entry_point]->data, &m_rx_payload_buffer[2],
                  m_rx_fifo.p_payload[m_rx_fifo.entry_point]->length);

     which suggests data index ==  [2].

So, which index is correct? What am I missing?

Thanks.

[Sigurd]

Hi!

I don't see the issue, m_rx_payload_buffer is a uint8_t buffer, not a nrf_esb_payload_t

It should hold total ESB payload defined as

This is how the application layer sees the packet, it's not actually sent over-the-air exactly like that. 

[astomi]

Well, eveything is byte size.Given that esb dpl uses LENGTH and S1 fields (promoted to 2 bytes), &m_rx_payload_buffer[2] will give me esb payload, not actual payload. App data would be &m_rx_payload_buffer[7] then?