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Using Launchpad back Channel UART as a USB-Serial Converter

Nura
Intellectual 285 points
Other Parts Discussed in Thread: TUSB3410

 

Hello Forum,

 

I have few programs based on 8051 and  programmer works on DB9 port, but my new PC doesn't have one. One solution would be to buy a USB-to-Serial converter (which use FTD or Silabs chips). I have 2 Launch pads and was wondering if i could use one of them as USB -to-Serial converter to be used with the 8051 programmer.

 

Read forum posts about the max baud of back channel uart on Launchpad being 9600.  My programmer works on 56700 baud. 

 

I did a loop back (connected TXD to RXD on Launch pad Board) check on launch pad at 56700 baud  in hyperterminal and the characters appeared correctly at this speed.

 

But why is it mentioned in the forum posts that the Back channel supports only upto 9600, is this the limit imposed by TUSB3410 Chip or the Target Msp430 which uses timer UART.

 

i'll have to do some level shifting as 8051 works on 5V and Launch pad signals are 3.5V ( simple P.divider will suffice)

 

Regards,

 

Nura

 

 

  • Guru 227245 points

    Nura said:
    I did a loop back (connected TXD to RXD on Launch pad Board) check on launch pad at 56700 baud  in hyperterminal and the characters appeared correctly at this speed.

    THat is surprising.

    True, the hardware serial connection through USB supports 56k. But this is from PC to the 1612 FET chip on the LaunchPad.
    The backchannel UART to the target MSP is done by bit-banging the otehrwise unused I/O port lines of the TUSB interface chip (by the specific TUSB firmware), and this is limited to 9600Bd. Just because the software in the TUSB chip isn't faster.

    Are you sure you didn't just see the local echo on HyperTerm while the serial connection was simply dead?

    Nura said:
    is this the limit imposed by TUSB3410 Chip or the Target Msp430 which uses timer UART.

    AFAIK the TUSB chip (see above). The software UART uses 2400Bd only.

  • in reply to Jens-Michael Gross
    Genius 3060 points

    There was some discussion about this in the 43oh forums

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