• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 83 subscribers
  • Views 645 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

F28M35 can SCI dataformat be inverted

Harm Verhagen
Prodigy 210 points
Other Parts Discussed in Thread: TMS3705

Hi,

We try to drive a tms3705  from the dsp on a  F28M35 concerto.

We have connected the tms3705 SCIO pin to the GPIO28 pin of the F28M35, and configured the GPIOMUX2 to use it as SCIRXDA.  We drive the tms3705 TXCT line from GPIO29 (configured as output).

We are able to drive the tms3705 device. (We see the expected signals on the SCIO line).

(we pull down TXCT, see the diag byt on SCIO, after 50ms  pull up TXCT and see a bit train coming pn SCIO.)

problem:

We are not able to read the serial data on SCIO into the F28M35. We keep on getting the SCI break-detect flag

When reading the docs I see a mismatch in signals of the tms3705 and F28M35.

From the tms3705 docs [1]  Figure 2:  the SCIO  pin is low by default, and the serial data is send by pulling up, and down... and then   pull it low again.

From the F28M35 SCI documentation [2] Figure 15-3, I see that SCI  expects the RX to be high by default, get the data by going down/up/down/up etc...  and then end high again.

Is it possible that this is indeed my problem ?  Should I invert the signal of the tm3705 SCIO before feeding it into the concerto ? Or is there a way I can get the concerto to accepts this inverted serial sigals ?

[1] http://www.ti.com/lit/ds/scbs881b/scbs881b.pdf    

[2] Concerto Technical Reference Manual.PDF  chapter 15

Regards,

Harm Verhagen

  • 0
    Expert 2115 points

    hi Harm,

    never heard of inverted uart signals. but guess there is a first time for everything.. 

    1. are the connections all right? tx-rx and rx-tx

    2. Is there an internal bit that inverts the signals? could be in the peripheral settings or in the gpio settings?

    3. try loopback. short the tx and rx signals and run an example code to see if you are receiving what you are transmitting.. 

    4. i think there is also an internal loopback bit that you can try.. 

    vivek

  • 0
    TI__Mastermind 22025 points

    Harm,

    To the best of my knowledge there isn't a way to invert these signals internally.  I think your best bet is to use an external inverting buffer to invert the signal.

    Trey