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cc2540/41 UART hardware

Dag.FF2
Intellectual 290 points
Other Parts Discussed in Thread: CC2541, CC2511, SN65C3243

Hello,

I have a simple resistor voltage divider as an interface between a PC's (TxD) port (±12-V) and the Keyfob's (RxD) port (±3-V).

 

      [ PC (RS-232 - TxD) ]  --->  [ (±12-V) | VOLTAGE DIVIDER INTERFACE | (±3-V) ]  --->  [ Keyfob (UART - RxD) ]

 

The data received in the Keyfob UART buffer is corrupted; where a hex 0x01 is received as 0x7f.

Can the cc2541 Keyfob UART hardware handle bipolar levels or do they need to be unipolar?  Please advise.  Thanks.

  • 0
    TI__Guru** 105180 points
    Hello Dag,

    This is related to your other thread: e2e.ti.com/.../1661387

    I will check with the HW team on your HW question, but I think it may be simpler to develop your system SW using the SmartRF05 eval board which has onboard UART terminals. Also, it may be helpful if you can provide logic analyzer plots as well as scope plots of your UART waveform.

    Best wishes
  • 0 in reply to JXS
    Intellectual 290 points

    Hello JXS,

    Indeed it is related to the other thread: just seeking much needed help from the community.

    Based on your response, I examined the SmartRF05 eval board design circuit and saw that it uses a transceiver [SN65C3243] for the RS-232 communication.  Data received at RIN1 of the transceiver is passed to ROUT1, which has an inverting driver at the output.  The ROUT1 output connects to EM_UART_RX (P1_5 of cc2511).

    Is the data received by the cc2511 UART buffer automatically inverted?

    Are the cc2511 and cc2541 UARTs similar?

    Could this be the reason why the data received by the cc2541 using the voltage divider circuit becomes inverted, where a hex 0x01 gets transmitted over-the-air as hex 0x7F?

    Please advise.  Thanks.

  • 0 in reply to Dag.FF2
    Intellectual 290 points

    Hello JXS,

    I have resolved the UART hardware issue.  Albeit indirect, thanks for help.