p.s. - I'm currently running a patched version of kernel version 4.4.110... 
for the BB-X15, but I believe the underlying principles are the same 
between the BBB and BB-X15 with respect to UART (except for the pinmux 
which is more straight forward to configure in BBB world).

On Monday, March 5, 2018 at 9:12:06 AM UTC-6, Jeff Andich wrote:
>
> Hi,
>
> There have been a number of posts on here on how to switch between the 
> 8250 and OMAP drivers.  Above in this same thread, Robert showed which 
> defines within the kernel defconfig file to change, and I experimented with 
> this and was able to see and use /dev/ttyO* instead of /dev/ttyS*.  I had 
> to search for and swtich additional defines, as initially, I ended-up 
> losing my console and still had /dev/ttyS*..  If you look through the 
> following post, you can see how I switched from the 8250 to the OMAP 
> driver.   Someone else on here proposed a way to have a mixture of OMAP and 
> 8250 serial drivers, but I haven't been brave enough to try that yet.
>
> https://groups.google.com/forum/#!topic/beagleboard/JGIm0Ej6jDI
>
> I never attempted to get full-blown hardware flow control up and running, 
> since our hardware board has RS485 chips which only have the DE pin 
> connected.  RTS and CTS lines don't interconnect the different parties on 
> the MODBUS network in our case, only the RS485 differential signals (e.g. 
> TXp, TXn).  
>
> Initially we connected GPIO lines to the DE pins, but then more recently, 
> our hardware engineer swapped out GPIO lines for the  "dedicated RTS" line 
> for a given UART.  
>
> One thing that's really interesting, IMO, is if you use a dedicated RTS 
> line (e.g. UART5 RTSn), you can still toggle RTS from the application layer 
> **using the 8250 driver**.  Whereas when I attempted to use  a GPIO line 
> and couple that to the UART through the UART device tree fragment (refer to 
> the above thread for an example), I was not able to toggle the RTS line 
> with the 8250 serial driver, but only the OMAP serial driver.  So as a test 
> I installed python-serial on my beagleBoard-X15.  When I issued 
> serial_object.setRTS(False/True) which was connected to DE on the 485 chip, 
> I would see the chip transmit and not transmit using the 8250 driver.  But 
> when using the GPIO line for RTS, I could only switch between transmit and 
> receive on the 485 chip when I compiled in and used the OMAP drivers.
>
> On Monday, March 5, 2018 at 7:12:50 AM UTC-6, erc...@gmail.com wrote:
>>
>> Hi Micka,
>>
>> We are having lots of trouble with RS485 with Kernel 4.4.x or kernel 
>> 3.8.13.
>>
>> Is there any guideline about how to use OMAP rather than 8250 or can you 
>> please explain the steps how can we do that?
>>
>> On Tuesday, April 26, 2016 at 10:00:19 AM UTC+3, Micka wrote:
>>>
>>> I dont know about 8250, but omap work well. I'm more confident about 
>>> omap handling the gpio than the driver 8250.
>>>
>>> I've been using omap for rs485 since the driver 3.8 and I've nothing to 
>>> complain about. 
>>>
>>> I will also switch to the driver 8250 when it will be ready ( a lot of 
>>> test need to be done )
>>>
>>>
>>> Micka,
>>>
>>>
>>>
>>> Le mar. 26 avr. 2016 08:05, 'Artur Festyn' via BeagleBoard <
>>> beagl...@googlegroups.com> a écrit :
>>>
>>>> Hi Micka.
>>>> no ttyO, its 8250 driver.
>>>> shouldn't 4.5 kernel work after these patches are applied or is it 
>>>> still too early?
>>>>
>>>> -rw-r--r--  1 root root 1440 Apr 21 12:26 
>>>> 0001-tty-serial-8250-fix-RS485-half-duplex-RX.patch
>>>> -rw-r--r--  1 root root 8243 Apr 21 12:26 
>>>> 0002-tty-serial-8250-make-UART_MCR-register-access-consis.patch
>>>> -rw-r--r--  1 root root 2743 Apr 21 12:26 
>>>> 0003-serial-mctrl_gpio-add-modem-control-read-routine.patch
>>>> -rw-r--r--  1 root root 1347 Apr 21 12:26 
>>>> 0004-serial-mctrl_gpio-add-IRQ-locking.patch
>>>> -rw-r--r--  1 root root 7924 Apr 21 12:26 
>>>> 0005-tty-serial-8250-use-mctrl_gpio-helpers.patch
>>>>
>>>> the last one clearly states that use of any gpio as rts should be 
>>>> possible
>>>>
>>>>
>>>> 2016-04-26 6:54 GMT+01:00 Micka <micka...@gmail.com>:
>>>>
>>>>> Can you show me what this command show : 
>>>>>
>>>>> dmesg|grep ttyO*
>>>>>
>>>>> I repeat only omap driver work for rs485
>>>>>
>>>>> Le mar. 26 avr. 2016 00:40, 'Artur Festyn' via BeagleBoard <
>>>>> beagl...@googlegroups.com> a écrit :
>>>>>
>>>>>> It is easy and already disabled.
>>>>>> My question is about RS485 and custom gpio to drive DE pin of RS485 
>>>>>> chip.
>>>>>>
>>>>>>
>>>>>> 2016-04-25 23:22 GMT+01:00 evilwulfie <evilw...@gmail.com>:
>>>>>>
>>>>>>> read this. disabling I2C2 is not as easy as using an overlay
>>>>>>> if you are not using capes sure but IMHO is always best to leave the 
>>>>>>> default things enabled and just work with overlays
>>>>>>>
>>>>>>>
>>>>>>> http://www.embedded-things.com/bbb/enable-canbus-on-the-beaglebone-black/
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 4/25/2016 2:09 PM, 'Artur Festyn' via BeagleBoard wrote:
>>>>>>>
>>>>>>> Honestly I don't know. I though this might be useful info :) 
>>>>>>> Three is no problem to disable I2C-2, but I am using those pins for 
>>>>>>> CAN0.
>>>>>>> That is why I want to use custom gpio to drive RS485 DE which 
>>>>>>> doesn't work.
>>>>>>>
>>>>>>> 2016-04-25 21:56 GMT+01:00 William Hermans <yyr...@gmail.com>:
>>>>>>>
>>>>>>>> *cat /proc/tty/driver/serial*
>>>>>>>>
>>>>>>>> *serinfo:1.0 driver revision:*
>>>>>>>> *0: uart:8250 mmio:0x44E09000 irq:158 tx:2451 rx:0 RTS|CTS|DTR|DSR*
>>>>>>>> *1: uart:8250 mmio:0x48022000 irq:159 tx:24 rx:0 CTS|DSR|CD|RI*
>>>>>>>> *2: uart:8250 mmio:0x48024000 irq:160 tx:0 rx:0 CTS|DSR*
>>>>>>>> *3: uart:unknown port:00000000 irq:0*
>>>>>>>> *4: uart:8250 mmio:0x481A8000 irq:161 tx:2 rx:1 brk:1 CTS|DSR*
>>>>>>>>
>>>>>>>> *5: uart:unknown port:00000000 irq:0*
>>>>>>>>
>>>>>>>> What is this supposed to mean ? That says UART0 has RTS, CTS, etc, 
>>>>>>>> but they're not connected to anything. So the CTS on UART1 means 
>>>>>>>> nothing. 
>>>>>>>> Because it's connected to I2C-2, which I'm sure you would have all 
>>>>>>>> kinds of 
>>>>>>>> fun disabling I2C-2 . . .
>>>>>>>>
>>>>>>>>
>>>>>>>> On Mon, Apr 25, 2016 at 1:14 PM, 'Artur Festyn' via BeagleBoard <
>>>>>>>> beagl...@googlegroups.com> wrote:
>>>>>>>>
>>>>>>>>> cat /proc/tty/driver/serial 
>>>>>>>>> serinfo:1.0 driver revision:
>>>>>>>>> 0: uart:8250 mmio:0x44E09000 irq:158 tx:2451 rx:0 RTS|CTS|DTR|DSR
>>>>>>>>> *1: uart:8250 mmio:0x48022000 irq:159 tx:24 rx:0 CTS|DSR|CD|RI*
>>>>>>>>> 2: uart:8250 mmio:0x48024000 irq:160 tx:0 rx:0 CTS|DSR
>>>>>>>>> 3: uart:unknown port:00000000 irq:0
>>>>>>>>> 4: uart:8250 mmio:0x481A8000 irq:161 tx:2 rx:1 brk:1 CTS|DSR
>>>>>>>>> 5: uart:unknown port:00000000 irq:0
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> 2016-04-25 21:12 GMT+01:00 Artur Festyn <fes...@googlemail.com>:
>>>>>>>>>
>>>>>>>>>> I can't use RTS/CTS pins on UART4 because I need HDMI. 
>>>>>>>>>> New RS485 patches suppose to help to use any gpio as RS485 RTS 
>>>>>>>>>> and in fact any gpio for any UART as RTS/CTS.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> 2016-04-25 21:00 GMT+01:00 evilwulfie <evilw...@gmail.com>:
>>>>>>>>>>
>>>>>>>>>>> any reason you want to use uart1 ?
>>>>>>>>>>>
>>>>>>>>>>> if you use uart4 you can use the whole uart tx rx and rts. 
>>>>>>>>>>> trying to bitbang rts for rs485 on uart1 sounds hard 
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On 4/25/2016 12:24 PM, 'Jan Kinkazu' via BeagleBoard wrote:
>>>>>>>>>>>
>>>>>>>>>>> So i compiled (bb-kernel, all patches) and installed 
>>>>>>>>>>> 4.5.2-bone4  
>>>>>>>>>>> I have modified am335-boneblack.dts and compiled it.
>>>>>>>>>>>
>>>>>>>>>>> #include "am335x-peripheral-ttyS1.dtsi"
>>>>>>>>>>> #include "am335x-bone-pinmux-ttyS1.dtsi"
>>>>>>>>>>>
>>>>>>>>>>> &am33xx_pinmux {
>>>>>>>>>>>         uart1_pins: pinmux_uart1_pins {
>>>>>>>>>>>                 pinctrl-single,pins = <
>>>>>>>>>>>                         /* P9_23: uart1_de */
>>>>>>>>>>>                         BONE_P9_23 (PIN_OUTPUT_PULLDOWN | 
>>>>>>>>>>> MUX_MODE7)
>>>>>>>>>>>                 >;
>>>>>>>>>>>         };
>>>>>>>>>>> };
>>>>>>>>>>>
>>>>>>>>>>> &uart1 {
>>>>>>>>>>>         pinctrl-names = "default";
>>>>>>>>>>>         pinctrl-0 = <&uart1_pins>;
>>>>>>>>>>>         status = "okay";
>>>>>>>>>>>         rts-gpios = <&gpio1 17 GPIO_ACTIVE_HIGH>;
>>>>>>>>>>>         rs485-rts-active-high;
>>>>>>>>>>>         rs485-rx-during-tx;
>>>>>>>>>>>         rs485-rts-delay = <1 1>;
>>>>>>>>>>>         linux,rs485-enabled-at-boot-time;
>>>>>>>>>>> };
>>>>>>>>>>>
>>>>>>>>>>> RS485 doesn't work, what do I do wrong?
>>>>>>>>>>>
>>>>>>>>>>> Kind regards
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Friday, 12 February 2016 15:33:40 UTC, Taceant Omnes wrote: 
>>>>>>>>>>>>
>>>>>>>>>>>> I would like to use RS485 with the BBB. 
>>>>>>>>>>>>
>>>>>>>>>>>> root@beaglebone:~/test# uname -a 
>>>>>>>>>>>> Linux beaglebone 4.1.15-ti-r40 #1 SMP PREEMPT Thu Jan 7 
>>>>>>>>>>>> 23:32:17 UTC 
>>>>>>>>>>>> 2016 armv7l GNU/Linux 
>>>>>>>>>>>>
>>>>>>>>>>>> I am using the kernel above. Its source code is at 
>>>>>>>>>>>>
>>>>>>>>>>>> <https://github.com/RobertCNelson/linux-stable-rcn-ee/tree/4.1.15-ti-rt-r40>
>>>>>>>>>>>> https://github.com/RobertCNelson/linux-stable-rcn-ee/tree/4.1.15-ti-rt-r40
>>>>>>>>>>>>  
>>>>>>>>>>>>
>>>>>>>>>>>> ... however it does not include the changes in this patch: 
>>>>>>>>>>>>
>>>>>>>>>>>> <https://github.com/RobertCNelson/bb-kernel/blob/am33x-v3.8/patches/fixes/0007-omap-RS485-support-by-Michael-Musset.patch#L30>
>>>>>>>>>>>> https://github.com/RobertCNelson/bb-kernel/blob/am33x-v3.8/patches/fixes/0007-omap-RS485-support-by-Michael-Musset.patch#L30
>>>>>>>>>>>>  
>>>>>>>>>>>>
>>>>>>>>>>>> Which kernel should I use that includes the changes in the 
>>>>>>>>>>>> patch or 
>>>>>>>>>>>> something similar? 
>>>>>>>>>>>>
>>>>>>>>>>> -- 
>>>>>>>>>>> For more options, visit <http://beagleboard.org/discuss>
>>>>>>>>>>> http://beagleboard.org/discuss
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>>>>>>>>>>
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