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TUSB3410 in RS485 mode?

Vladimir Dimov
Prodigy 70 points
Other Parts Discussed in Thread: TUSB3410, SN65HVD11, SN65HVD20

Hello,
I have some questions regarding the TUSB3410, working in RS485 mode.
Our design is based on the schematic, shown on page 19 in the TUSB3410's datasheet:
SOUT, SIN, RTS and DTR are connected to the RS-485 transceiver (SN65HVD11).
For the firmware we have tried one, that we found in TI's forums (0842.RS-485.zip), but the device works only in transmit direction. It seems that this firmware controls only the RTS pin. DTR remains unchanged all the time.
Could you please provide us with a working firmware and PC driver pair for RS485 bridge aplication?

Best regards,
V. Dimov

  • 0
    TI__Genius 11255 points

    Hello Vladimir,

      Please note the RS485 use hardware control protocol since it’s a half-duplex operation, could you please verify that you are using this configuration on your software? Please follow the recommendation and in page 12 - figure 3-3 on the Data Manual. (http://www.ti.com/lit/ds/symlink/tusb3410.pdf) 

      Also could you please provide us your schematic in order to verify that everything is correct

      How are you loading the firmware its burned on a external EEPROM or its loaded by the driver? 

     Could you please point us where is the RS485 that you download? Anyhow  please fin the RS485 firmware on the following FTP site. 

    ftp://pickup@ftppickup.ti.com/pub/share/uquanan 

    Name: pickup

    Password: piurh!  

    Regards,

    Roberto

  • 0 in reply to Roberto Diaz
    Prodigy 70 points

    Hello Roberto,

    thank you for the reply! These are my schematic, the firmware that I'm using and the .bin file for the EEPROM:

    3051.TUSB3410_485.pdf

    5040.0842.RS-485.zip

    2234.EEPROM_bin.zip

    My schematic is according to the recommendation in page 12 on the data manual.

    I think that firmware you pointed me to is the same, that I'm currently using (I compared the both files binary). The firmware in my case is burned on an external 128k EEPROM. I also modified the .inf file for the driver - I commented out the lines, which contained the "umpf3410.i51". As result - the device works, but only RTS signal changes its state. DTR is always HIGH, so the 485-transceiver works only in one direction.

    Today I tried to cut the DTR trace from the tusb3410 and to use only RTS for both RE and DE pins on the 485-transceiver (shorted pins 2 and 3 on transceiver). This way the device works as expected - in both directions. But should I leave it this way? What could be the reason for the DTR signal not working?

    Regards,

    Vladimir

  • 0 in reply to Vladimir Dimov
    TI__Genius 11255 points

    Hello Vladimir, 

                Sorry for the delay on this, the reason of why it’s not working is because the DTR (active low) signal  transceiver on the example (page 12 ) is denied (DTR_n) and the transceiver that you are using (SN65HVD11) this signal is “active high”. 

                    You can leave the signal shorted pins 2 and 3 on transceiver since RTS/DTS are opposed signals, please take a look on the following graphic

     

     

    Regards,

    Roberto

  • 0 in reply to Roberto Diaz
    Prodigy 70 points

    Hello Roberto,

    Thank you very much for the answer!

    Regards,

    Vladimir

  • 0 in reply to Roberto Diaz
    Intellectual 420 points

    Hi Roberto,

    I'm also designing a USB to RS232/RS485/RS422 device, there I've used SN65HVD20 for RS485. For Receive Enable and Driver Enable I've used some logics with DTR and GPIO. 

    RE =  P3.3 P3.1 + (NOT (P3.1)) (NOT(P3.3 DTR))

    DE = ((NOT (DTR)) P3.3 ) (NOT(P3.3 P3.1))

    But It's not working. Could it be possible for you to explain me ?

    Thanks and Regards.

    Kshitij Gupta

    P3.3 P3.1 1Y(RE) 3Y(DE) Interface
            RS-485 RS-232
    0 0 1 0 OFF OFF
    0 1 0 0 OFF OFF
    1 0 DTR DTR ON OFF
    1 1 1 0 OFF ON