On Sunday, May 26, 2013 1:53:01 PM UTC-4, [email protected] wrote: > > I'd like to find a good and detailed source of information on how to > create a well-integrated BBB Cape design. I have put together a bare-bones > cape which is just an EEPROM chip running off the BBB's 3.3v line. The > EEPROM contains my correctly formatted data and does indeed appear to be > recognised in the output from *dmesg*. However, I am now a bit stuck. > > Following a couple of articles on the web I managed to bodge together a > working ".dtbo" file and this appears to work. My prototype board does > show up in `cat /sys/devices/bone_capemgr.9/slots` after a reboot, which is > great :). > > But I'm at a bit of a loss as to what I should do next. I'd like to put > an ATMega microcontroller onto my shield (running from the BBB's 3.3v rail) > and have it talk to the BBB using two IO pins to form a simple TX/RX uart. > The ATMega side of this is no problem, I've done this many times, but the > BBB side is unknown to me. > > Take a look at the BB-UART1 DTS script (in /lib/firmware), it shows how to configure UART1 for use. Once you've compiled the .dtbo for your cape and put it in /lib/firmware, if you have the right part # and revision info in the EEPROM, then the capemgr should properly load the .dtbo and you'll see a device /dev/ttyO1 (for UART1). At this point, you can test it by running minicom and configuring the port to use /dev/ttyO1 (with 115200,8,N,1 with no flow control etc) and you should be able to talk to your ATmega.
NOTE: There's a 60 delay when the capemgr tries to load your dtbo as there's a race condition with the eMMC cape (which contains the root filesystem!) and it hangs for 60 seconds before giving up, loading the eMMC cape which allows filesystem access. At that point, it does retry your cape and will load the .dtbo, but the 60s hang is **very** annoying. There were some patches applied a while ago, but I don't know if they have shown up yet. Besides, changing the 60 timeout requires a custom kernel. The only other option to skip the 60s delay is to compile your dtbo into the kernel -- I haven't yet figured out how to do this! Hope this helps, -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.
