Hello:) I have a new problem. I use now a script to read the data from the external device (see my post before: http://beagleboard.org/Community/Forums?place=msg%2Fbeagleboard%2FpfRLpoOEv9M%2Fj4LJHPGOJgAJ ). This script is just a copy of the script in the linked tutorial. I just changed the baudrate, data bits and the input/output strings.
This script works, but only sometimes. Unfortunately it doesn't work always. I think it works with a success rate of 20%. In the other 80% there is just no output from the external device, which means it didn't receive the request string "/?!\r\n". Has anyone an idea why? I also did a dirty-patch for ser2net to use this GPIO-thing, but also with ser2net i only have a success rate of +/- 20%. The externel device works without any problems, because if i use the RS485<->USB-converter every data readout is successful. Is there another trick with this GPIO-thing? In the tutorial i did not find any other problem sources. Thank you & Best regards Benj Am Mittwoch, 26. August 2015 22:49:22 UTC+2 schrieb Alexander Hiam: > > The BeagleBone's omap-serial driver doesn't support RS-485 DE/RE control > with the RTS flow control signal. Instead it has an RS-485 mode using a > GPIO pin for DE/RE control, and has a modified serial_rs485 struct from the > standard serial driver. You have to use ioctl on the corresponding > /dev/ttyOx file to put the serial driver in RS-485 mode and tell it which > pin to use, and you also have to take care of muxing the pin to GPIO mode. > > So with the jumper in the RTS position that would be the GPIO signal that > shares the pin with the UART4 RTS signal, so that's GPIO0_9 on P8.33. Or > you can put it to the GPIO1_16 position and use GPIO1_16 instead. (I > believe GPIO1_16 > > There's a tutorial here: > http://inspire.logicsupply.com/2014/09/beaglebone-rs-485-communication.html > > Also, I believe RS485B is the inverting output, so you have your +/- > swapped. > > On Wednesday, August 26, 2015 at 2:41:49 PM UTC-4, [email protected] > wrote: >> >> Hello, >> >> I have a BeagleBone Black with a "Serial Cape" ( >> http://www.logicsupply.com/eu-en/cbb-serial/). This cape supports RS-485 >> which i'm interested in. Before i had this cape, i used a >> RS-485-to-USB-converter. >> >> >> My problem: >> I try to read some data from an external device. It's very simple: The >> request is just "/?!\r\n" and then i get the data. >> >> With the RS485-to-USB-Stick i used this serial port configuration (with >> ser2net): >> /dev/ttyUSB0 9600 7DATABITS EVEN 1STOPBIT >> >> With the cape i tried this configuration: >> /dev/ttyO4 9600 7DATABITS EVEN 1STOPBIT >> >> Unfortunately this first try didn't work. I didn't get any response. I >> also tried this configuration: >> /dev/ttyO4 9600 7DATABITS EVEN 1STOPBIT RTSCTS >> >> I set the jumpers on the cape like this: >> J8: RS485 >> J7: UART4 RTS >> >> The RS485+ wire is connected to the RS485B port, and the RS485- wire is >> connected to the RS485A port. >> ( >> https://docs.google.com/document/d/1sgurQ-7gLyn7g-Kg983NRM0aDkYEqHqy9dmrieX_RUM/edit >> >> page7) >> >> To get a better overview i made a photo: >> >> >> <https://lh3.googleusercontent.com/-DGOBBHIo6sM/Vd1xuVsgc_I/AAAAAAAAAEE/JS4oAhPYoOk/s1600/IMG_20150826_091607_mod.jpg> >> >> >> At the bottom of the picture there is the RS485-to-USB converter. It just >> has two ports which i used to connect the RS485 wires. >> >> I think the board itself should work, because if i execute "cat >> /sys/devices/bone_capemgr.*/slots" i can see it. >> >> My question: >> Do i do something wrong? Maybe someone else has used this cape with >> RS485? I thought it should be almost as easy as with the USB converter? >> >> >> Thank you for any help >> >> Best regards >> Benj >> >> -- 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]. For more options, visit https://groups.google.com/d/optout.
