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Change HCI H4 Transport UART baud rate for CC256x

Matthias Ringwald
Expert 1475 points

HI!

How can I change the UART baud rate used when communicating with the CC256x? I'm sure there's a vendor-specific command for that... :)

Best

 Matthias

  • 0
    TI__Prodigy 495 points

     

    Mattias,

    You can use the command "HCI_VS_Update_UART_HCI_Baudrate (0xFF36)"

    The format is: { 0x36, 0xff, 0x04, DD, CC, BB, AA}, where AABBCCDD represents the desired baud rate. All HCI data is in little endian as usual.

     

    regards,

  • 0 in reply to Kevin Jones
    Expert 1475 points

    That command worked.

    Thanks! 

  • 0 in reply to Kevin Jones
    Intellectual 270 points

    Hello Kevin, I have basic question to ask you: UART is used for data commuting for HCI for Bluetooth, I have wondering the baud rate is enough for various protocols and profiles above on that? I learned for generic UART, the max. baud rate is 115200 and for HCI scenario, the baud rate usually is set lower than max., is the story true?

    I assume that the SCO is routing via different channel called I2S or PCM, even it's true, do you think the baud rate for HCI still enough? 

    In other words, my concern could be illustrated on this question: the bandwidth of Bluetooth(>1Mbps) is larger than HCI(112.5Kbps), does it mean that the bottleneck of HCI will block the received data which should be sent to protocols/profiles layer?

    Sorry about asking stupid questions.

    Cheers,

    mh 

  • 0 in reply to Minghua YAO
    TI__Guru* 85400 points

    Hi,

    115200 is enough for most profiles (assuming you can compromise on the throughput)... However, for some profiles ( like A2DP streaming) a higher baud rate is desired. The CC256x supports a maximum baud rate of 4Mbps. Please see the below snippet from the datasheet

    "The maximum baud rate of the UART module is 4 Mbps; however, the default baud rate after power up is
    set to 115.2 kbps. The baud rate can thereafter be changed with a VS command. The device responds
    with a command complete event (still at 115.2 kbps), after which the baud rate change occurs."

    As you told, this has no bearing on SCO though.

    Regards,
    Gigi Joseph.

  • 0 in reply to Joseph Gigi
    Intellectual 270 points

    Hello Joseph,

    me, again:) thanks again that you inspired me in another thread.

    As you know that EM2 connector has two headers, one is about data exchanging(UART, SPI, I2C), the other is about AUD streaming.

    Even as you explained that the throughput of UART could afford A2DP, does A2DP pass in UART instead of AUD in current design? If yes, why don't use AUD? A2DP and HFP are mutually exclusive, shouldn't conflict with each other.

    btw, could you provide the link of the snippet you quoted? Thanks!

    Cheers,

    mh

     

  • 0 in reply to Minghua YAO
    TI__Guru* 85400 points

    Hi MH,

    A2DP passes via the UART as they are L2CAP (ACL/Data) packets...

    The snippet is from the CC256x datasheet - http://www.ti.com/lit/ds/swrs121d/swrs121d.pdf
    Btw, there is also an option to use the Assisted A2DP mode (explained in the data sheet)

    Regards,
    Gigi Joseph.

  • 0 in reply to Joseph Gigi
    Intellectual 270 points

    Hi Joseph, thanks for your explanation, very helpful! thanks!

    Cheers,

    mh