Can only a portion of a BS2 fail?

SteveWoodrough

For some reason I cannot high / low an LED on PIN 3 of my BS2.· All others I/O's·0-15 except 3 work fine.· Is it possible for only a single I/O to fail?·

Thanks...Steve

Jonathan

Yes, it is quite possible. I have done it myself [noparse]:)[/noparse] . The two most common reasons are:

1) Overcurrent. If you put too heavy a load on the pin it will blow. Use a transistor, MOSFET or relay to power the load.

2) Back EMF. If running a motor, relay or solenoid, switching the load on and off creates a spike of high voltage that can eat a Stamp pin. Use a protection diode to prevent.

What were you doing with the pin that blew?

Jonathan

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www.madlabs.info - Home of the Hydrogen Fuel Cell Robot

SteveWoodrough

Don't know but I'll be more careful next time...Thanks

Beau Schwabe

SteveWoodrough,
·
Before I worked at Parallax, we had a PCB board house create a batch of bad boards which ended up wiping out pin 14 on many BS2's due to a short on the board.· Fortunately we had a few spare pins and were able to make a manual board modification using another pin, and adjust the software.· The project/study using the boards lasted for 6 months and we never had any ill issues.
·
Now, from a layout perspective, and knowing what I know now, my advice·would be to use it at your own risk.· Usually a damaged pin due to over current·is localized to the pin and will not affect other pins, but this also depends on the severity of the damage.· An MPE (major pin event) can cause latching problems within the silicon substrate that are generally problematic and can affect the entire chip.


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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

SteveWoodrough

Good advice, and I'll keep an eye out for issues.

Fortunately I will not be using the stamp in passenger aircraft guidance and landing navigation routines! However, I will have a great excuse the next time my code does not work....hardware issue!!!