On Thursday, 9 February 2017 13:30:23 UTC+1, oetti133 wrote: > > For testing I ordered the Waveshare RS485-CAN Cape > <http://www.waveshare.com/rs485-can-cape.htm>. >
Ehm, I noticed in its schematic <http://www.waveshare.com/w/upload/1/16/RS485_CAN_Schematic.pdf> that it ties the R-output of the CAN receiver directly to the UART_TX net. They did this presumably because can1_{rx,tx} use the same pins as uart1_{tx,rx} (note the difference in direction), although it's a mystery to me why they routed it through their uart jumper selection since only one jumper position is correct for can. This unnecessarily renders the simultaneous use of CAN and RS485 (via some uart other than uart1) on this cape impossible, but worse yet is that when configuring it for RS485 use there is a drive conflict between UARTn_TXD of the cpu and the R-output of the CAN receiver. Maybe it happens to work if the can receiver loses the fight over that net, but it's not going to be good for the health of either component. > Most tutorials using an older Debian version are using ttyOx to access the > serial ports (old OMAP-driver?), but based on this output I have to use > ttySx with the newer 8250 driver for my commands instead? > As you noticed it creates symlinks from ttyOx to ttySx when using the 8250-omap driver, so using ttyOx would still work fine and has the benefit of also working with the omap-serial driver (where ttySx would not). I'm personally still not convinced about the merits of using the crusty 8250 driver instead of one dedicated to the omap uart. I haven't evaluated the quality of the omap-serial driver either though, but if I were to write a driver for this uart I would certainly use it in a way that avoids its 8250 legacy as much as possible rather than embracing it. I tried to send/receive messages between the UARTs using minicom, screen > and python scripts, but i can't see any messages at the receiving > interface. Measuring the sending UARTs TX with an oscilloscope I also can't > see any signals. > This is odd, we use them without problem on a 4.9 kernel using 8250-omap. Double-check your pinmux configuration, e.g. using my show-pins script <https://github.com/mvduin/bbb-pin-utils>, and try making sure the port is sanely configured, e.g.: stty -F /dev/ttyO1 sane raw clocal cread -crtscts 38400 cs8 -parenb -cstopb echo -e 'Hello world!\r\n' >/dev/ttyO1 Matthijs -- 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/42c43fe5-5833-4945-a667-5f80b5348cab%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
