• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 32 subscribers
  • Views 605 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

ISO1452: Not Getting Correct data Over RS485 using ISO1452.

SARJU BHATNAGAR
Expert 1020 points
Part Number: ISO1452
Other Parts Discussed in Thread: ISO1412

Hi TI,

We are facing an issue while using ISO1452 (RS485 and RS422 transceiver) in our custom board. we have a device which works on RS485. here is the command 

FF 08 XX XX XX XX 0B (Modified) 

and below is the response which slave should return.

FF 1C 00 02 XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX 06 80 80 63 6C (Modified)

but instead of only response it returns CMD+RESPONSE. (command which is sent, followed by response). I am not able to understand why it is returning CMD with response. why not only response.

here is the images 

 

and here  is the circuitry which we are using 

kindly help out.

Br,

Sarju Bhatnagar

  • 0
    TI__Intellectual 1960 points

    Hi Sarju:

    Thanks for posting your question on E2E.

    Looking at your schematic, I see that the termination resistors (R79 and R204) are not populated. Please make sure that the RS-485 bus is terminated properly according to the Figure 50 and Figure 51 of the ISO1452 datasheet. Also, I'd recommend that the series R80, R150, R163 and R163 are replaced with <10Ohm. 120Ohm in series on the RS-485 bus will significantly degrade the signal integrity.

    However, I don't believe that the issue you're seeing is related to the schematic. One of my colleague from Code Composer Studio team will further assist you with debug.

    Regards,

    Dushmantha

  • 0 in reply to Dushmantha Rajapaksha
    TI__Intellectual 1960 points

    Hi Sarju:

    Could you also confirm which MCU/controller and the protocol you use with ISO1412? Also, how many nodes do you have on the RS-485 bus?

    Thanks,

    Dushmantha

  • 0 in reply to Dushmantha Rajapaksha
    Expert 1020 points

    Hi Dushmantha,

    First of all, thank you so much for your reply, answer to your question, 

    we are not using MCU/Controller, we are giving UART (using USB to TTL Convertor) input to the ISO1412, and IC is Converting it to RS485 , which is connected to the single Node/slave(works on RS485).

    To send data over UART we are using DockLight V2.3 (Eval)  software. so we don't need to write any code at this (checking) stage.

    this technique works well, we have checked it , but with different converter module. we are bit new with ISO1412.

    please do let us know the issue.

    Thanks again,

    sarju bhatnagar

  • 0 in reply to SARJU BHATNAGAR
    TI__Intellectual 1960 points

    Hi Sarju:

    Thanks for providing the additional details.

    ISO1412 is a galvanically isolated TTL to RS-485 electrical converter (and vice-versa) with no intelligence built in (ISO1412 is just a buffer). ISO1412 has no understanding of any higher layer protocol. Apart from my previous recommendation on the RS-485 termination, I don't see any concerns with your schematic that includes ISO1412.

    I'd recommend that you reaching out to DockLight software / USB to TTL converter vendor for support on software protocol. 

    Regards,

    Dushmantha