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Topic: Arduino Dmx occasional random erratic behavior (Read 307 times) previous topic - next topic


Hi, I've got an Arduino mega 2560 and am using this shield:


Sorry if this is posted in the wrong section.

I'm using the dmx simple library and it is set up to output on pin 4. I have tried using other pins with a long jumper and the issue remains when it occurs.

The issue:
Sometimes when sending dmx info to my lights from the board and shield listed above, data won't send or it sends random data unless I lightly touch one or more of the pins on the Arduino.

-I have used known working code multiple times
-I've used different Arduino mega 2560's to test this issue
-I've tried different lights, dmx cables, tried mic xlr cables, tried different usb-b cables with and without rf chokes
-I've tried it with and without my laptop plugged in (trying to see if it was a ground loop as the shield is non isolating), and even plugged my Arduino into a USB phone charging dongle

-I do have my Arduino sitting next to me on my couch which is either fake leather or a thin real leather, I don't know if that could carry any amount of capacitance that could mess with the serial ports and cause it to spaz out.

I only chock this up to capacitance since having my finger touching pin 2 or occasionally pin 4 (or the pin that I have designated for the output to the dmx shield which uses a max485 chip without an optoisolator) will make the issue go away. Also unsure if it's just a lack of enough power being supplied.

I've already emailed the supplier of this board to get any insight into this issue, just waiting on a reply.

I would appreciate any ideas as to what could be causing this.

I'm posting this while on break at work but I can post the code later tonight if anyone needs to see it.
Food for thought.


We need to see the code and the wiring.  This sounds like missing pullup or pulldown resistors but could easily be something else.

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