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CC2520 TX FIFO management with packets larger than 128 (Fifo size)

Mathieu Schneider
Expert 1385 points
Other Parts Discussed in Thread: CC2400, CC2520, CC2500

Does anyone have some good suggestions on managing the TX FIFO when sending packets greater than the FIFO size (128Bytes).  I see that in Rx the Microcontroller can monitor the FIFO and FIFOP lines.   However, there doesn't appear to be any similar means for TX mode.  I did this a number of years ago on the CC2400 and that radio had the ability to use the FIFO and FIFOP line for both TX and RX modes.

  • 0
    TI__Genius 13620 points

    It is not possible to send longer packets than 128 bytes with CC2520.

    You mentioned you did this with CC2400. That device is more similar to the CC2500 transceiver, as none of them are 802.15.4 radios. With CC2500, you can send as long packets as you like.

  • 0 in reply to M
    Expert 1385 points

    I am quite surprised as the datasheet indicates that one could receive larger packets.  Could I not just ensure that the Tx FIFO doesn't empty while transmitting?

    I am not trying to be argumentative just grasping at straws now.

     

  • 0 in reply to Mathieu Schneider
    TI__Genius 13620 points

    Could you please specify where in the datasheet you find info about packets longer than 128 bytes? It should be pretty clear on this matter. Take a look at chapter 18, in particular 18.1, and chapter 20.

  • 0 in reply to M
    Expert 1385 points

    Thanks Mozart for continuing this discussion.

    You win Mozart!

    I suppose the descriptions of the FIFO and FIFOP lines were familiar to me from the CC2400. 

    I am grasping now.   Would this statement be true:

    As long as I read the RXFIFO before the RXFIFO over flows I can receive any number of consecutive packets.  Therefore, If I set the FIFOP threshold to 60 bytes. and start reading the bytes on FIFOP interrupt before the FIFO overflows I should be able to "effectively" receive larger than 128 byte packets.  On the Tx Side, after the radio's TXFIFO  is preloaded and then STXON is issued, the Micro can start loading sending the next packet to the TXFIFO so long as the next packet's data doesn't overrun the active packet.  Once the TXCOMPLETE is issued the micro can then issue the next STXON command and continue filling the remainder of the packet.

     

     

     

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