Ah, that's very helpful, thanks.
Ideally I was hoping to use the RTS signal though. From what I had read
that seemed to be the standard for UART RS485 mode in the Linux kernel, but
looking into the omap_serial driver it looks like it wasn't implemented (on
3.8 at least).
On Wednesday, January 22, 2014 3:36:08 AM UTC-5, Mickae1 wrote:
>
> Hi,
>
> About the RS485 support on the BBB, you have to modify the driver omap
> serial and control the gpio that you want. But if you want a quick
> solution, i already made a patch for that :)
>
> You just need to :
>
> git clone git://github.com/RobertCNelson/linux-dev.git
> cd linux-dev/
> git checkout origin/am33x-v3.8 -b tmp
>
> in the linux-dev folder, you have the KERNEL folder. You just need to put
> the file in the patches/omap folder and edit the patch.sh :
> :
>
> ${git} "${DIR}/patches/omap/000X-omap-rs485-support.patch"
>
>
> in the linux-dev folder :
> cp system.sh.sample system.sh
> edit the file system.sh:
>
> be sure that you have :
> ##For TI: OMAP3/4/AM35xx
> ZRELADDR=0x80008000 <== uncomment !
>
> the correct path to your sdcard :
> MMC=/dev/sdc
>
>
>
> to build the kernel , you just need to use this command : ./build_kernel.sh
>
> to install the new kernel to your sdcard : ./tools/install_kernel.sh
>
>
>
>
> On Tue, Jan 21, 2014 at 10:52 PM, Alexander Hiam
> <[email protected]<javascript:>
> > wrote:
>
>> Yeah I noticed that. I was hoping to go the ioctl route because I'm
>> working on a cape that gives the option of RS232 or RS485 on UART4, so the
>> runtime switching would be great.
>>
>> Hopefully I'm just doing something stupid, but I can't get it to work
>> through ioctl. I've tried in both C and Python on an Angstrom image with
>> 3.8, this testing image, and an old Angstrom with 3.2 on the original BB.
>> The tests I'm trying are here:
>> https://gist.github.com/alexanderhiam/8548894
>>
>> On all three bones the C ioctl() call raise errno 25. On the two with 3.8
>> the Python ioctl() call raises 'IOError: [Errno 25] Inappropriate ioctl for
>> device' and on the bone with 3.2 it raises 'IOError: [Errno 22] Invalid
>> argument'.
>>
>> I was under the impression that you had to enable the RS485 ioctl
>> settings when building the kernel, but I can't remember where I got that
>> idea and I haven't actually tried it yet :p
>>
>> Perhaps I should start a new thread for this one...
>>
>> -Alex
>>
>>
>> On Tuesday, January 21, 2014 3:49:38 PM UTC-5, RobertCNelson wrote:
>>
>>> On Tue, Jan 21, 2014 at 2:33 PM, Robert Nelson <[email protected]>
>>> wrote:
>>> > On Tue, Jan 21, 2014 at 2:14 PM, Alexander Hiam <[email protected]>
>>> wrote:
>>> >> Thanks Robert, I just booted it for the first time and so far so
>>> good. I see
>>> >> that there's still no ioctl for RS485 mode on the UARTs though. Is
>>> there a
>>> >> reason RS485 support isn't enabled on the BB kernel builds?
>>> >
>>> > There is no module for "rs485" you need to call the omap-serial driver
>>> > with the proper ioctls
>>> >
>>> > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-
>>> stable.git/tree/Documentation/serial/serial-rs485.txt?id=
>>> refs/tags/v3.8.13
>>>
>>> Looks like you can enable it on boot time too..
>>> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-
>>> stable.git/tree/Documentation/devicetree/bindings/serial/
>>> rs485.txt?id=refs/tags/v3.8.13#n28
>>>
>>> Regards,
>>>
>>> --
>>> Robert Nelson
>>> http://www.rcn-ee.com/
>>>
>> --
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>
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