On 09/16/2014 06:40 AM, [email protected] wrote:
Michel Lavoie <[email protected]> wrote:
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I strongly recommend that you read Adafruit's guide regarding the BBB's
device tree overlay. It really help me put this all together:
https://learn.adafruit.com/introduction-to-the-beaglebone-black-device-tree/overview
You will find there why and how to modify your uEnv.txt file in order to
enable ttyO1. In mine, the last line looks like this:
...
optargs=coherent_pool=1M; capemgr.enable_partno=BB-UART1,BB-SPIDEV0
optargs=coherent_pool=1M; capemgr.enable_partno=BB-UART1,BB-SPIDEV0
optargs=coherent_pool=1M; capemgr.enable_partno=BB-UART1,BB-SPIDEV0
optargs=coherent_pool=1M; capemgr.enable_partno=BB-UART1,BB-SPIDEV0
The Adafruit UART IO documentation specifically says that it *does*
export the overlays:-
The Adafruit IO Python library will export the UART device tree
overlays as a convenience. There are five serial ports brought to
the expansion headers (UART3 only has a single direction, TX), and
one (UART0) with dedicated headers that aren't available to use in
your Python programs.
... but not all the UARTs work.
In addition the use of the letter O in the device name is just silly! :-)
The devices it creates are called /dev/ttyO1, /dev/ttyO2, etc. with
the letter O. There's not a mention anywhere that it's a letter
rather than a digit and given the context it's second nature to assume
it's a zero. Still I did spot that eventually.
Yes, the O and not zero threw me for a loop when I was first setting up
serial on the BBB. I have no clue where/why that choice was made.
I haven't looked into the Adafruit library, my hunch here is that to use
uart5 you will have to disable HDMI as the pins used for that uart are
in the HDMI group. As noted above uart3 is TX only, and again those
pins fall within the HDMI group.
For what it's worth I referenced that info from here.
https://github.com/derekmolloy/boneDeviceTree/blob/master/docs/BeagleboneBlackP8HeaderTable.pdf
https://github.com/derekmolloy/boneDeviceTree/blob/master/docs/BeagleboneBlackP9HeaderTable.pdf
Mike
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