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TRS3253E-EP: Not able to receive and transmit data through DB9 connector using Waveshare USB to RS232 converter

Rajesh K R
Prodigy 10 points
Part Number: TRS3253E-EP
Other Parts Discussed in Thread: TRS3253E

Tool/software:

I am using TRS3253E-EP IC in my custom board which is connected to DB9 connector from that i am trying transmit and receive data using USB to RS232 convertor. 

When i tried to transmit and receive by enabling CTS and RTS in STM32 CubeMX i am not able to do it, Similarly if i disable CTS and RTS I can transmit and receive data through USB to TTL converter.

By similar way i tried with Waveshare USB to RS232 converter by enabling and disabling CTS and RTS in both case not able to transmit or receive data through DB9 connector.   

Actually i want to transmit and receive the data in TRS3253E via DB9 connector with a Waveshare Rs232 converter. please refer the attachment and help me out.

MCU : STM32H7IGT3

OS : windows

IDE : stm32 cube ide. 

  • 0
    Guru 316690 points

    The TRS3253E-EP works only on the electrical level; it converts between logic signals (e.g., RS232_RTS) and RS-232 signals (e.g., TCSC1_BB_RS232_RTS). It does not change the meaning of these signals.

    From your description, the TRS3253E-EP appears to work correctly. The problem probaly is that the STM32 and the WaveShare do not agree on what the protocol on the CTS/RTS signals is, or that these signals are not wired correctly.

  • 0
    TI__Genius 13492 points

    Hi Rajesh, 

    Thanks for posting on E2E!

    Looking over your schematic, I am not seeing any issues, and I agree with Clemens points here. The RS-232 standard only defines the electrical/physical layer and the data layer is determined by the designer. Since TX/RX is working for you, the transceiver is unlikely to be the source of the problem. 

    I would double check that the CTS/RTS pairs are properly connected throughout your system. I would check your DB9 connector pins in particular. It should look something like this:

    Let us know if you have any other questions!

    -Ethan

  • 0 in reply to Ethan Sempsrott
    Prodigy 10 points

    Hi Ethan,

    Thanks for your reply. 

    Now i am able to transmit and receive data using waveshare RS232 converter only when both CTS and RTS are disabled in STM32 ioc file. But if i enable both CTS and RTS i am not able to transmit but i can receive data from docklight. 

    If i enable only RTS i am able transmit and receive data but same way if i enable only CTS i am not able to transmit data  but i can receive from docklight.

  • 0 in reply to Rajesh K R
    TI__Genius 13492 points

    Hi Rajesh, 

    Were you able to confirm that the pinout was correct from the MCU/RS-232 transceiver all the way to the USB interface? 

    If you are concerned that the transceiver is the source of the problem, please probe the RIN/ROUT and DIN/DOUT pins that are problematic with an oscilloscope and share the waveforms.

    I would also confirm that the RTS/CTS implementation is the same for the Waveshare and STM32.

    Regards,

    Ethan

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    Hi Clemens,

    Thanks for your reply. 

    Now i am able to transmit and receive data using waveshare RS232 converter only when both CTS and RTS are disabled in STM32 ioc file. But if i enable both CTS and RTS i am not able to transmit but i can receive data from docklight. 

    If i enable only RTS i am able transmit and receive data but same way if i enable only CTS i am not able to transmit data  but i can receive from docklight.

  • 0 in reply to Rajesh K R
    Guru 316690 points

    The TRS3253E-EP works correctly, so there is not much we can do to help you.

    I can only suggest to check the RTS/CTS signals with an oscilloscope or logic analyzer to find out which of the two other devices does not work as it should.