On Wednesday, October 16, 2013 8:39:30 PM UTC-4, [email protected] wrote: > > Thank you very much for the info, it really helped me understand whats > going on. It looks like it would be nice to have one of those FTDI-USB > adapters. > > I have another question now - what the difference between the TX/RX pins > on J1 versus all of the serial pins on P8/P9? (P9-11 UART4_RXD, P9-13 > UART4_TXD, etc..) >
They just belong to different UARTs. The connections on J1 are wired up to UART0 which mapped to /dev/ttyO0 and used as the serial console. If you want to use the other UARTs (which are not enabled by default), then you first need to enable them by loading the appropriate device tree overlay. If you look in /lib/firmware, you'll see a number of pre-prepared sample dtbo files for configuring different things. For example, if you want to load BB-UART5.dtbo to enable UART5 (P8 pins 37,38) you need to add the following to the kernel command line (in uEnv.txt in the mmcblk0p0 FAT/boot partition): capemgr.enable_partno=BB-UART5 The reason for this is that the AM335x has many more functions than pins, so you need to do something called pinmuxing in which you enable the features you want by configuring the pins into the appropriate mode. It used to be that if the features you wanted were not available by default, you had to edit the platform file in the kernel sources and build your own kernel, now fortunately, you can do this with the device tree overlays (.dts files). If you want to get into the details of serial ports, pinmuxing and device tree overlays, take a look here: http://hipstercircuits.com/enable-serialuarttty-on-beaglebone-black/ -W. -- 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/groups/opt_out.
