Re: [Gumstix-users] Pololu USB to Serial on HWUART on Breakout-GS - advice

[David H. <da...@sw...>]

Dave Hylands wrote:
> Hi David,
>
> On 5/29/07, David Hearn <da...@sw...> wrote:
>   
>> I'm trying to connect a Pololu USB to Serial converter to the HWUART
>> ports of the breakout-gs, connected to a connex400xm (with a tweener too).
>>
>> The info at: http://www.pololu.com/products/pololu/0391/ gives all the
>> pin outs.  I've connected on the Pololu board I've connected GND, TX and
>> RX to the breakout-gs's HWUART ports GND, TXD and RXD respectively
>> (HWUART being the 2nd one down (60pin connector top) on the right hand
>> side - directly below PWM1/PWM0 etc.
>>     
>
> You may need to cross Tx and Rx. Tx is on output on the gumstix, and
> Rx is an input on the gumstix.
>
> Looking at the web page for the voltage converter you're using, it
> also as Tx as an output and Rx as an input.
>
> So you need to connect Tx on the gumstix to Rx on the voltage
> converter, and Rx on the gumstix to Tx on the voltage converter.
>   
I tried it that way first (thinking TX is output from Gumstix, and RX 
being input into converter), but changing it to TX-TX, RX-RX didn't make 
any difference (still didn't work).  I think it's the GPIO config hinted 
in the Wiki.
>> I then installed all the Pololu drivers etc and I'm able to open up that
>> port in Windows now.  However, I was hoping to just do something as
>> simple as "echo "Hello" > /dev/ttyS3" to test it was working, however
>> nothing arrives (and no error).
>>     
>
> Also make sure that you have hardware flow control disabled on the PC side.
>   
Already done.
>> I note in the Wiki that "The HWUART can be routed to two different sets
>> of pins. By default, it is routed to a set of pins shared with the
>> BTUART (and connected to the Gumstix's Bluetooth module, if present). It
>> can be routed to a different set, freeing up the HWUART and leaving the
>> BTUART to control the Bluetooth module. However, this second set of pins
>> is shared with the PCMCIA/CompactFlash interface, and thus cannot be
>> used with expansion boards which have a CF card interface, or a network
>> interface (including the wifistix). Currently, this includes all
>> connex-only expansion boards.
>>
>> The Gumstix Linux kernel maps the HWUART to /dev/ttyS3."
>>
>> This makes me wonder whether I need to do anything to enable the HWUART
>> before I can use it, as it might otherwise be connected to the BTUART?
>>     
>
> You can check the configuration of the GPIO pins for HWUART by doing:
> modprobe proc_gpio
> cat /proc/gpio/GPIO48
> cat /proc/gpio/GPIO49
>   
What I see is:
# cat /proc/gpio/GPIO48
48      AF2     out     set
# cat /proc/gpio/GPIO49
49      AF2     out     set
> GPIO48 should show something like AF1 out, and GPIO49 should show AF1 in.
>   
Okay, so I then try:

# echo "AF1 out" > /proc/gpio/GPIO48
Set (AF1,out,set) via /proc/gpio/GPIO48
# echo "AF1 in" > /proc/gpio/GPIO49
Set (AF1,in,set) via /proc/gpio/GPIO49
# cat /proc/gpio/GPIO48
48      AF1     out     set
# cat /proc/gpio/GPIO49
49      AF1     in      set

I now understand the Wiki entry about those AF1 bits now.  I read it as 
being needed for GPIO use rather than enabling it for serial.  These 
settings appear to reset on reboot, I can look into that later.
> Note, even you were connected up properly, you won't see anything from
> the host if you don't have some software on the gumstix connected to
> /dev/ttyS3.
>
> I'd recommend using sertest:
> <http://docswiki.gumstix.com/Sample_code/C/Serial>
>
>   
I've just tried that app, using ./sertest -p ttyS3 -b 9600 and with the 
PC end of the adaptor running a 9600 with flow control disabled, yet I 
see no comms either way.  I'm using a serial monitoring program too and 
that's showing no comms either.

Any suggestions?

Thanks

David