i.MX6UL Kernel 4.14.115 RS485

[ralfglaser]

Hi @all,

has anybody a working RS485 configuration for i.MX6UL running Linux Kernel 4.14.115 (DTS entry, example source) or any other kernel version?

We have tried various versions of the DTS file entry and finally end up with the same result everytime:

Once we open the port (using cat or whatever software) the RTS line goes low and stays low. Except when using stty to set -hupcl, in this case RTS will stay high no matter what.

So the following questions arise:

Has anybody ever successfully (read as beeing able to send AND receive data) used the RS485 driver?

If yes, how does it need to be configured and used?

Are we missing something essential here?

Thanks and best regards,

Ralf

[Bio_TICFSL]

Hello Ralf,

CTS_B pin should be used to control Rec or Send direction, not RTS_B. See reference manual, please!

Generalities, Figure 53-12. RS-485 driver connectioni.MX6ULL Reference Manual :

The CTS_B pin can be used to control RS-485 output driver outside the chip.

http://www.nxp.com/docs/en/reference-manual/IMX6ULLRM.pdf 

It's a bit disturbing that these lines :

rs485-rts-active-high;

rs485-rts-delay = <1 1>;

are in fact controlling the CTS pin.

Best regards

[ralfglaser]

Hi,

thanks for your fast response.

I'm actually using CTS_B, otherwise stty -hupcl would make no difference (i checked the RTS_B line anyways just to be sure and it doesn't do anything as expected).

The question remains the same: Has anybody used the RS485 successfully and can provide the required DTS file entry, example source etc.)?

Best regards,

Ralf