Re: [Gumstix-users] Noise on Rx pin of ttyS2 (STUART)

[VaibhavGhadiok <vai...@gm...>]

There are no fluorescent lights. Only light bulbs. The amount of garbage data
b touching the Rx pin is quite a lot. It just streams across the screen. I
am not sure if EMI could be attributed. I seriously don't know. 

The Zigbee module does work at 3.3 V. I have a Regulator to give me 3.3 V
from 5 V.

I am just not being able to isolate the fault.

There is a huge capacitor on my power line of the robostix that I had
installed to get a cleaner supply for my other sensors. I had removed it but
that was seemingly not the culprit.

Another possibility, I have all the three boards stuck together (Verdex Pro,
Netpro, robostix). But there might not be a way to test the boards by
removing them. I will not be able to attach the robostix board to the
gumstix if I use a tweener board until and unless there is a way to access
STUART using the Tweener board.

I am really at a loss. I will keep trying things.


Dave Hylands wrote:
> 
> Hi Vaibhav,
> 
> On Sun, May 23, 2010 at 11:25 AM, VaibhavGhadiok
> <vai...@gm...> wrote:
>>
>> I am connecting them to a Zigbee module (Xbee-Pro). So, logic level.
>> My initial thought was that it might not be getting enough current. But,
>> it
>> is able to transmit which would require more current. Anyways, this
>> doesn't
>> even matter as I see gibberish on the screen (running sertest) when I rub
>> the Rx pin with my finger with nothing attached to either the Rx or Tx
>> pin.
> 
> That's pretty much to be expected, especially if you're in a room with
> flourescent lights. The human body is a great receptacle for the 120
> Hz EMI emitted from these.
> 
>> Using the Xbee module, I am able to send characters from my gumstix using
>> sertest and receiving them on a host computer (with another Xbee Pro
>> attached to it) running a software provided by Maxstream called X-CTU.
>> The
>> Xbee is connected using a USB Board (not Max-232) The software does work.
>> Also, the zigbee modules work as I can see the Tx and Rx lights blinking
>> when I send a character. I have swapped them, just to check.
> 
> I'm assuming that you've also connected ground between the robostix
> and the Zigbee module?
> 
> The datasheet I looked at implied that the zigbee modules are 3.3v,
> while the robostix is 5v. Is this true for your module? If so, do you
> have a voltage converter?
> 
> -- 
> Dave Hylands
> Shuswap, BC, Canada
> http://www.DaveHylands.com/
> 
> ------------------------------------------------------------------------------
> 
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> 

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