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Topic: Issues with Arduino Zero Digital Inputs (Read 171 times) previous topic - next topic

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

DrAzzy

Did you forget to connect the grounds?
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TomGeorge

Hi,
Did you check the 3.3V at the pullup resistors?

How far away is the reedswitch and the LDO?
Do you have a scope to look at the inputs?
If not, what voltage do you measure on the inputs with your DMM in AC mode, before and when the fault occurs?

Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

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