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CC2543: How to use Basic mode with fix data length?

Part Number: CC2543


I want to use Basic mode with fix data length on CC2543.

I base on the CC254x PER example code and modify it to Basic Mode with fix data length to transmit data out (PRF_TASK_CONF.MODE =00).

In this mode, the packet format should no length field and fix the transmit data length. The time of transmit should be the same when I put different value on first byte into TXFIFO.

But in my measurement the transmission time is follow the first byte( length field). Measured the time of transmit using OBSSEL0 and RFC_OBS_CTRL0 = 0x09 (TX_active).Is it normal? Or configuration should be modified? My code attached as



  • Hi Jack,

    I am not understand what the problem is. Can you please clarify?

  • Hi Fredrik,

    There are 4 modes for radio operation of CC2543. 

    00: Basic mode, Fixed length
    01: Basic mode, Variable length
    10: Auto mode, 9-bit header
    11: Auto mode, 10-bit header

    I use the mode 01 before (Basic mode , variable length) , and it work well.

    But my customer want to reduce first byte(length field) then I try to modify to mode 00 ( Basic mode with Fixed length).

    If configured correctly, the transmission data length is fixed and the transmission time will be fixed in my thinking.

    I'm using the Radio Out setting to measure the transmission time, and I got a strange result. The transmission time will related to the first byte(Length field on mode 01).

    If the transmission time is correct, this means that my configuration has some errors.

    My question is 

    Q1 : Is there any errors on my configurations ?

    Q2 : Is there a test code for Basic mode with fixed length? 



  • The first byte in the TX FIFO is always a length byte. In variable length mode, the length is transmitted over the air; in fixed length mode, it is not. See Section 23.8.2 of for details.

  • Hi Hec,

    I got it. This is my misunderstanding of TXFIFO.
    Thanks for you answer.