[PD] digital write problem in Pduino

Derek Holzer derek at umatic.nl
Wed Oct 8 17:59:31 CEST 2008

Attached is a diagnostic patch which demonstrates the problem. This 
problem can be demonstrated using only the Arduino board with a single 
LED (plus current reducing resistor of 1.5K) connected from pin 2 to GND.

At 7 simultaneous [metro]s, the on-board LED at Pin 13 starts to blink, 
even when it has not been sent any messages. After that, a single LED on 
Pin 2 will start to blink sporadically, especially with more randomized 
[metro] intervals. If the [metro] controlling the LED on Pin 2 is 
switched off, it will continue to blink if other [metro]s are running.

Clearly this is a case of message collisions, even though the [comport] 
object does not report any TX-OVERRUNS.

I'm not too skilled with writing code for the Arduino, so I have no way 
of running something standalone right now to see if it can be isolated 
from the board.

I'd really like to have a solution or workaround to this problem, as 
it's quite an unexpected bug!!!!

thanks + best!

Charles Henry wrote:
> On Wed, Oct 8, 2008 at 9:38 AM, Derek Holzer <derek at umatic.nl> wrote:
>> The blink interval is something in the area of 200-500 miliseconds,
>> certainly slow enough for the comport. Could it be trouble with some of
>> the objects in the [arduino] abstraction?
> Hi, Derek,
> One thought that occurred to me: it takes around 16-20 ms to send a
> message to the arduino and recieve a message back (which has to do
> with the FTDI chip).  This is a round-trip time--I'm not sure what the
> delay time is like for data traffic going in one way.  Perhaps those
> delays are adding up, when you've got 10 separate LEDs to control?
> Have you considered making a test program on the arduino to blink the
> LEDs at different rates and see if the problem persists?  That would
> isolate the communications from the actions performed.
> Chuck

derek holzer ::: http://www.umatic.nl ::: http://blog.myspace.com/macumbista
---Oblique Strategy # 70:
"Feedback recordings into an acoustic situation"
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