Can some one explain this... (how an intact silicone coated ground wire can trigger programming mode)

J

JimKazmer

Well-known member
I am using a Teensy 4.0 in combat robotics. In the past, our Bot would get thrown against the ceiling and then smash into the floor, and that force was enough to cause the rubber "programming mode" button to depress due to its own inertia (forcing the Teensy into programming mode). We removed the button (including the small conducting plate under the button). However, at a recent event the programming mode was activated. In this video (link below), you can see me reproduce/trigger programming mode by pushing a silicone clad ground wire against the programming pin. My apologies to you, the video was initially produced for people who may not be familiar with the Teensy. I know how to avoid the issue in the future (cover those pins, external pull-up), but I'd like to understand how/why this can happen.
Program mode entered via insulated ground wire.
It is not easy to reproduce... the first time (off camera), it happened in about 15 seconds; the second time (in the video) it occurred after 45 seconds; the third time (off camera) it took me almost five minutes to trigger it.
Here is the link to the fight where it occured: Fight Robots Fight!
 
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similar but not as difficult to explain:
I had a wire connected to program button, and The teensy running on battery that could be put into program mode by switching on a soldering station. It seemed that the wire acted like an antenna and the EM impulse of the 'switching on the soldering station' triggered the programming mode.
Your case may be different, but you could overcome incidental programming mode by pulling programming pin to 3.3V (e.g. with a resistor).
 
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