HI, I don't have time to read your mail, but If you want to use rs485 on kernel 4.1/4.4 you have to use the omap driver and not 8250( which is the default ).
Look at this link : http://lxr.free-electrons.com/source/drivers/tty/serial/omap-serial.c?v=4.4#L1558 You can see that the property "*rs485-rts-active-high" *is used only on the driver omap and not 8250 . with that the rs485 work well ^^ micka, Le lun. 25 avr. 2016 à 15:12, florian.feldbauer85 via BeagleBoard < [email protected]> a écrit : > Hey all, > > I did some further tests. > Actually none of the screens from my scope looks like I would expect it... > > Picture 1 shows the result, if I try to read something on the bus with a > 14s timeout (nothing was sended on the bus...) > Pic1 <http://www.ep1.rub.de/~florian/rs485_test_reading_timeout.png> > Picture 2 shows the same, but this time there were messages send over the > bus. After 49 bytes, the beagle bone toggles the DE/!RE gpio to high for > unknown reasons (the test program is still reading from the UART interface) > Pic2 <http://www.ep1.rub.de/~florian/rs485_test_reading.png> > Picture 3 shows the test, where the BeagleBone is sending > Pic3 <http://www.ep1.rub.de/~florian/rs485_test_sending.png> > and finally picture 4 shows a test, where the BeagleBone should read > (timeout 3s) on the bus, then send something and again reading (with 3s > timeout)... > Pic4 <http://www.ep1.rub.de/~florian/rs485_test_3sRead-send-3sRead.png> > As you see, DE/!RS stays high after sending, although it should be low... > > In addition I would expect this line to be low when the port is not used, > but it's high.. > > I checked if there is any other process (or driver) accessing GPIO3_19 but > I could not find any... > > Any help is very much appreciated! > Florian > > > > > Am Freitag, 22. April 2016 15:22:48 UTC+2 schrieb > [email protected]: >> >> Hey all, >> >> I'm using the Debian Jessie image with kernel version 4.4.6-ti-r15 on my >> BeagleBone Black. >> >> To monitor our vacuum system in the lab, we need a RS485 interface, so I >> simply connected an ADM2682 RS422/485 line driver >> to UART4 of the BeagleBone using this Device Tree Overlay >> BB-UART4-RS485-00A0.dts >> <https://github.com/RobertCNelson/bb.org-overlays/blob/master/src/arm/BB-UART4-RS485-00A0.dts> >> (commit >> 16f76f7 on master branch) >> >> P9.27 is connected to the DE and !RE inputs of the chip. >> >> Using this for sending works just fine, but I have problems receiving >> messages over the bus. >> >> For testing I wrote a small C-program which should read on the bus until >> it gets two times a timeout. >> The reading is done via select-call with a 5 second timeout. >> The device on the other end of the bus is contentiously sending data over >> the bus. >> After receiving 49 bytes at most, the DE/!RE line goes up and my >> BeagleBone stops receiving any data... >> >> I've uploaded a screenshot of the scope showing the three signals from >> the UART interface >> Scope <http://www.ep1.rub.de/~florian/rs485.png> >> >> Does anyone has a clue what could go wrong? >> >> Any help appreciated! >> Regards >> Florian >> >> >> -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/4811b6af-b1dc-4909-a972-62f2c5f35fd2%40googlegroups.com > <https://groups.google.com/d/msgid/beagleboard/4811b6af-b1dc-4909-a972-62f2c5f35fd2%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CAF%2BMRtnDWBhktik7rsKTWhq8%2BX-ELEcBiwcDK4hdVopez44OFA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
