Hello,
I would like to get RS485 to work on my BBB which has kernel 3.8.13-bone79.
The steps are not clear to me especially since I have little experience
with embedded linux. I hit a wall when trying to load a modified version
of Robert Nelson's BB-UART4-RS485--00A00
<https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-UART4-RS485-00A0.dts>
overlay. I noticed that if I commented out any variables that have
reference RS485 (e.g. rts-gpio, rs485-rts-delay etc) the overlay loads fine.
How should I proceed? Am I supposed to apply a patch to omap-serial.c which
I can not even find on my BBB?
Please help!
Bolek
On Thursday, March 3, 2016 at 3:57:47 AM UTC-8, Micka wrote:
>
> Hi,
>
> I was the one that create the patch for the kernel 3.8 ^^ .
>
> And I figure it out how to make rs485 work on kernel 4.1 . It's rather
> simple :
>
> uart1_pins: pinmux_uart1_pins {
> pinctrl-single,pins = <
> 0x184 0x20 /* P9.24 uart1_txd.uart1_txd OUTPUT OK*/
> 0x180 0x20 /* P9.26 uart1_rxd.uart1_rxd INPUT OK*/
> 0x1a4 0x07 /* Uart1_Txen -> GPIO3_19 OK*/
> >;
> };
>
> &uart1 {
> pinctrl-names = "default";
> pinctrl-0 = <&uart1_pins>;
> status = "okay";
> rts-gpio = <&gpio3 19 GPIO_ACTIVE_HIGH>;
> rs485-rts-active-high;
> rs485-rts-delay = <1 1>;
> linux,rs485-enabled-at-boot-time;
> };
>
> and of course disable 8250 and enable omap driver.
>
> to test it ? echo "test test test" > /dev/ttyO1
>
>
> that work for me ^^
>
>
>
> Le mer. 2 mars 2016 à 21:59, Richard Krehbiel <[email protected]
> <javascript:>> a écrit :
>
>> USE KERNEL 3.8.13. I spent days trying to figure out why
>> 4.4.1/2/3-bone-rt-5 wasn't working. Selecting the omap-serial driver
>> (rather than the 8250-omap driver) won't work because some of the rs485
>> patches didn't get included in later kernels.
>>
>> Since last Thursday, my job was getting RS485 working on BBB.
>>
>> I used a MikroElectrinika MikroBUS cape*, and an RS485 Click** plugged
>> into mikroBUS socket 1. I actually rather like this setup.
>>
>> *http://www.mikroe.com/click/mikrobus-cape/
>> **http://www.mikroe.com/click/rs485-3.3v/
>>
>> For mikroBUS socket 1, RX and TX pins are routed to the Sitara uart2, and
>> the data direction control connects to J9 pin 14 (a.k.a gpio1[18], a.k.a.
>> "echo 50 >/sys/class/gpio/exports"). It's only necessary to load the
>> BB-UART2 overlay ("echo BB-UART2 >/sys/devices/capemgr.*/slots" or
>> "capemgr.enable_partno=BB-UART2" in the uEnv.txt boot file) and do your
>> programming.
>>
>> Use this for the RS485 setup structure:
>>
>> struct omap_serial_rs485 {
>> __u32 flags; /* RS485 feature flags */
>> #define OMAP_SER_RS485_ENABLED (1 << 0) /* If enabled */
>> #define OMAP_SER_RS485_RTS_ON_SEND (1 << 1) /* Logical level for
>> RTS pin when
>> sending */
>> #define OMAP_SER_RS485_RTS_AFTER_SEND (1 << 2) /* Logical level for
>> RTS pin after sent*/
>> #define OMAP_SER_RS485_RTS_BEFORE_SEND (1 << 3)
>> #define OMAP_SER_RS485_USE_GPIO (1 << 5)
>> __u32 delay_rts_before_send; /* Delay before send (milliseconds) */
>> __u32 delay_rts_after_send; /* Delay after send (milliseconds) */
>> __u32 gpio_pin; /* GPIO Pin Index */
>> __u32 padding[4]; /* Memory is cheap, new structs
>> are a royal PITA .. */
>> };
>>
>> ... because the omap-serial rs485 patches slightly enhanced the regular
>> struct serial_rs485 you find in sys/serial.h
>>
>> Here's my rs485 setup code (error checking omitted):
>>
>> struct omap_serial_rs485 rs485;
>> i = ioctl(m_fd, TIOCGRS485, &rs485); // whats' the current setup?
>> rs485.flags |= OMAP_SER_RS485_ENABLED; // Enable RS485 mode
>> rs485.flags |= OMAP_SER_RS485_USE_GPIO; // use a GPIO pin for
>> // direction control
>> rs485.flags &=
>> ~(OMAP_SER_RS485_RTS_AFTER_SEND|OMAP_SER_RS485_RTS_ON_SEND);
>> rs485.delay_rts_before_send = 0; // No delay from RTS-assert
>> before xmit
>> rs485.delay_rts_after_send = 0; // No delay after xmit until
>> RTS-negate
>> rs485.gpio_pin = m_pin; // select the direction control
>> pin
>>
>> i = ioctl(m_fd, TIOCSRS485, &rs485); // establish
>>
>> I built and installed kernel 3.8.13-bone79 this morning. Finally I'm
>> working well.
>>
>> On Friday, February 12, 2016 at 10:42:24 AM UTC-5, RobertCNelson wrote:
>>
>>> On Fri, Feb 12, 2016 at 9:33 AM, Taceant Omnes <[email protected]>
>>> 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
>>>
>>> You need to rebuild and swap these two configs:
>>>
>>> disable: CONFIG_SERIAL_8250_OMAP
>>>
>>> enable: CONFIG_SERIAL_OMAP
>>>
>>> > ... 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
>>>
>>>
>>> 485 is pretty much built-in to CONFIG_SERIAL_OMAP
>>>
>>> It's the last thing still being talked about for integration into
>>> CONFIG_SERIAL_8250_* for possibly 4.6.x
>>>
>>> > Which kernel should I use that includes the changes in the patch or
>>> > something similar?
>>>
>>> and use this overlay as reference, as it's been reported to work with
>>> that config chanage above..
>>>
>>>
>>> https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-UART4-RS485-00A0.dts
>>>
>>>
>>> Regards,
>>>
>>> --
>>> Robert Nelson
>>> https://rcn-ee.com/
>>>
>> --
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>
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