Electronics > Beginners

Strange behaviors with microcontroller digital inputs

(1/4) > >>

tyguy2:
Hello all,

I've embedded a SAMD21G (Basis for the Arduino Zero) into a PCB I've been designing. I've been using pins PA19 and PA18 (Arduino pins 12 and 10 respectively) to act as inputs for 2 different signals entering the device. The first is connected to a reed switch with an external 4.7k ohm pull up resistor with the reed switch connected to ground. The second is connected to a LDO's output to detect if a device external to the PCB has been powered on (schematics attached). This is attached to a 4.7k ohm pull down resistor. The issue I'm having is that after a few hours of operation, the micro begins to not accurately detect if these sources are high or low. Checking with a multimeter, I've noticed the voltages at the inputs are 1.53-ish volts for the reed switch and 1.23-ish volts for the LDO, rather than the standard 0v or 3.3v. Does anyone know what could be causing this and how I'd fix it?

Thanks

Kasper:
Is your 3.3V source still at 3.3V when the problem occurs?

tyguy2:
Yes, it remains at 3.3v

EEEnthusiast:
The LDO output going to 1.23 is surprising and it looks like the reference voltage of the LDO. Is there something which gets heated on the board? Also check the VIO supply of the microcontroller. Check if it is floating or some soldering issue. This is mostly coming from a power issue.

Twoflower:
Can you read back the IO-config of the controller of the pins in question? Just in case you're actually chasing a SW issue that by accident re-configures your input pin. But from the datasheet the pull-down would be too weak (about 40k) for the voltage you see.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod