RS-232 driver for GPIO

Wed May 15 13:46:06 UTC 2013

On May 15, 2013, at 9:40 AM, Tom Everett wrote:

> ok, just one further question.  It was basically guess work that enabled me
> to decypher that /dev/ttyu0 (sio0) was bound to uart0.  I presume there
> must be some simple way from the command line to query the OS and find out
> which hardware devices are bound to which /dev/ entries?

The unit numbers generally match the alias names in the FDT.

However, we don't note what the names for the nodes we're attaching to on FDT systems.  We really should, but we don't...

Warner

> On Wed, May 15, 2013 at 3:29 AM, Aleksandr Rybalko <ray at freebsd.org> wrote:
> 
>> On Tue, 14 May 2013 20:24:42 -0600
>> Tom Everett <tom at khubla.com> wrote:
>> 
>>> Did you mean 14 &15, or 14 & 16?
>> Yeah, right.
>> 
>> 
>>> ok so given this, I've done some reading.  I'm by no means a FreeBSD
>>> expert, so forgive me if I'm completely wrong.  I see this in the FDT:
>>> 
>>> /* UART0 */
>>> pins_uart0_a: uart0_a {
>>>      broadcom,pins = <14>, <15>;
>>>      broadcom,function = "ALT0";
>>> };
>> 
>> If you satisfied by single UART, you no need change that.
>> 
>> 
>>> 
>>> 
>>> and this:
>>> 
>>> chosen {
>>>              bootargs = "";                  /* Set by VideoCore */
>>>              stdin = "uart0";
>>>              stdout = "uart0";
>>>      };
>>> 
>> 
>> But that stdin and stdout direct kernel console messages to air by your
>> xbee :)
>> So you need comment it or set different in/out device.
>> 
>> 
>>> 
>>> So I interpret that to mean that uart0 is bound to pins 14, 15, and
>>> furthermore that the serial device bound to uart0 is bound to stdin and
>>> stdout.  In my /dev/ I see:
>>> 
>>> crw-------   1 root  wheel     0x1f Apr 27 13:42 ttyu0
>>> crw-------   1 root  wheel     0x20 Apr 27 21:42 ttyu0.init
>>> crw-------   1 root  wheel     0x21 Apr 27 21:42 ttyu0.lock
>>> crw-rw----   1 uucp  dialer    0x22 Apr 27 21:42 cuau0
>>> crw-rw----   1 uucp  dialer    0x23 Apr 27 21:42 cuau0.init
>>> crw-rw----   1 uucp  dialer    0x24 Apr 27 21:42 cuau0.lock
>>> 
>>> So, that is telling me that sio0 is bound to uart0, which is a serial
>>> console?
>> 
>> Yep.
>> 
>>> 
>>> If so, that means that I could use pins 14 & 15 for rs-232, but I would
>>> have to chose b/t using those pins to talk to another device (xbee), or a
>>> serial console?
>> 
>> if you will disconnect serial console you will have to choose between
>> control over network (SSH/telnet/etc) or graphic console (Display with
>> HDMI + USB keyboard).
>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> On Tue, May 14, 2013 at 5:17 PM, Aleksandr Rybalko <ray at freebsd.org>
>> wrote:
>>> 
>>>> On Tue, 14 May 2013 12:20:08 -0600
>>>> Tom Everett <tom at khubla.com> wrote:
>>>> 
>>>>> ok so the FDT definition would have to be added here?
>>>>> 
>>>>> 
>>>> 
>> http://svnweb.freebsd.org/base/head/sys/boot/fdt/dts/bcm2835-rpi-b.dts?view=markup
>>>>> 
>>>> 
>>>> Yeah, right.
>>>> 
>>>> But I have bad news. Both UARTs can be connected to pairs(tx+rx) 14+16,
>>>> 32+33, 40+41 and both UARTs can be connected to any of this pins.
>>>> But only 14, 16 and 40(PWM0) wired to ext.pin.
>>>> 
>>>>> 
>>>>> 
>>>>> On Tue, May 14, 2013 at 10:24 AM, Aleksandr Rybalko <ray at freebsd.org
>>> 
>>>>> wrote:
>>>>> 
>>>>>> On Tue, 14 May 2013 09:06:44 -0700
>>>>>> Adrian Chadd <adrian at freebsd.org> wrote:
>>>>>> 
>>>>>>> ... the r-pi actually has an RS232 port exposed via GPIO. It's
>>>>>>> only 3.3v but it's there.
>>>>>>> 
>>>>>>> Someone just needs to write up an SIO driver for it and then put
>>>>>>> the GPIO pins in question into RS232 "mode".
>>>>>> 
>>>>>> we have it already :) (console works on uart)
>>>>>> only FDT definition is required.
>>>>>> And maybe some fixes for boudrate setting and/or format setup
>>>>>> (bits/parity/stop bits/etc)
>>>>>> 
>>>>>>> 
>>>>>>> Yay multi-function GPIO pins!
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> adrian
>>>>>>> 
>>>>>>> 
>>>>>>> On 14 May 2013 08:58, Tom Everett <tom at khubla.com> wrote:
>>>>>>>> Good morning ARM mailing list.
>>>>>>>> 
>>>>>>>> I've been running FreeBSD on my Pi, and I've now got two XBee
>>>>>>>> Pros which I hope to connect.  XBee's communicate over RS-232.
>>>>>>>> 
>>>>>>>> https://www.sparkfun.com/products/8742
>>>>>>>> 
>>>>>>>> I see from the source tree that it was possible to attach the
>>>>>>>> iic driver to GPIO pins in software:
>>>>>>>> 
>>>>>>>> 
>>>> http://svnweb.freebsd.org/base/head/sys/dev/gpio/gpioiic.c?view=markup
>>>>>>>> 
>>>>>>>> I'm wondering, it is possible to connect the FreeBSD serial
>>>>>>>> driver for RS-2332 to GPIO in a similar way to how iic was
>>>>>>>> connected?
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> --
>>>>>>>> A better world shall emerge based on faith and understanding  -
>>>>>>>> Douglas MacArthur
>>>>>>>> _______________________________________________
>>>>>>>> freebsd-arm at freebsd.org mailing list
>>>>>>>> http://lists.freebsd.org/mailman/listinfo/freebsd-arm
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>>>>>>> _______________________________________________
>>>>>>> freebsd-arm at freebsd.org mailing list
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>>>>>> 
>>>>>> 
>>>>>> --
>>>>>> Aleksandr Rybalko <ray at freebsd.org>
>>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> --
>>>>> A better world shall emerge based on faith and understanding  -
>>>>> Douglas MacArthur
>>>> 
>>>> 
>>>> --
>>>> Aleksandr Rybalko <ray at freebsd.org>
>>>> 
>>> 
>>> 
>>> 
>>> --
>>> A better world shall emerge based on faith and understanding  - Douglas
>>> MacArthur
>> 
>> Good luck! And let us know how things is going :)
>> 
>> WBW
>> --
>> Aleksandr Rybalko <ray at freebsd.org>
>> 
> 
> 
> 
> -- 
> A better world shall emerge based on faith and understanding  - Douglas
> MacArthur
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