RS485 support on iMX6Q

[jameszt]

Dear all,

     I am working on RS485 support on IMX6Q + Yocto1.7 for some days, but it can't send data while receiving is OK. I am using minicom on both RS485 sides. I've read topics on this community about RS485 but they doesn't help yet. Please give me some advise.

     BTW, must RS485 work in 9-bit multidrop mode?  that is, bit 9 is used to transfer slave address? thanks a lot.
BRs,

James 

[art]

Please note that RS-485 (also known as EIA/TIA-485) is the physical level

standard that only defines the parameters of signal transferring media, but no

data transfer protocol and even no data unit structure. Some higher level logic

protocol, such as Modbus, ProfiBus or something like that, must lie over the RS-

485 physical media. So, check the protocol stack you use. Also, make sure that

a RS-485 compatible transceivers are present on all of your RS-485-based network drops.

Have a great day,
Artur

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[jameszt]

Hi Artur,

     Thanks! Since I am using the Linux Minicom tool to verify RS485 physical communication, can I disable parity(PREN=0) to disable 9-bit mode?  I don't think minicom support 9-bit mode. 

BRs,

James.

[art]

Yes, you can do it.

Best Regards,

Artur

[jameszt]

Hi Artur,

     iMX6 UART RS485 mode?   says that " The MDEN field only enables rs485 9 bit address mode and standard 485 multi drop will work quite happily without this particular feature."  Can I not set the MDEN but still want to enable rs485 w/o 9-bit mode?

I DON'T find people make RS485 work in DTE mode, because in DTE mode, CTS is input, so this pin can't be used to control rs485 tx/rx direction, am I right?

or do you have a rs485 success story in DTE mode? Thanks a lot!

BRs,

James.

[art]

Q. Can I not set the MDEN but still want to enable rs485 w/o 9-bit mode?

A. Yes, you can do it.

Q. I DON'T find people make RS485 work in DTE mode, because in DTE mode, CTS is input, so this pin can't be used to control rs485 tx/rx direction, am I right?

A. Yes, you are right.

Best Regards,

Artur

[jameszt]

Hi Artur,

        In DTE mode, the UCR2[12] controls CTS_B, which in turn controls UARTn_RTS_B, so we still have chance to use UARTn_RTS_B to switch RS485 Rx/Tx direction, right?

Do we have anyway to make CTS_B to connect to  UARTn_CTS_B  in DTE mode?

James