Teensy analog input not functioning properly

[RichardFerraro]

I have worked with ten+ teensy 3.1's.

I wired in a new Teensy 3.1 and found it reporting a continuous analog voltage (from a pot across 0 and Vin) in jumps (regardless of the analog pin). It would read sort of continuously from 0-30 then jump to 60, 127, 255, 500, 1023 with no values in between.

Trying a different teensy 3.1 did not show this behavior.

Sparkfun is replacing the part and was curious if anyone experienced this?

thanks,

Richard

There is no program to speak of:

void setup() {
Serial.begin(115200); // console
}

void loop() {

short val = analogRead(A0);
Serial.println(val);

delay(100);

}

 

[PaulStoffregen]

I've never seen anything like that.

I can tell you we test AREF and A0 on every Teensy 3.1 with analog voltages. The tester applies several different voltages to A0 and AREF and reads A10-A14. This is done while also applying test patters to all the digital pins (eg, 1 pin high, all the others low, and 1 pin low, all the others high). In every test, all the digital pins have to read correctly, and the 5 analog pins have read approx close to the ideal number, which varies as the voltage on AREF changes.

If the ADC inside the chip were only working with specific numbers, I'm pretty sure that test would fail.

Then again, it's entirely possible some very strange & unusual damage happened. But this is indeed a very strange problem. I've never heard a report of anything quite like it.

 

[RichardFerraro]

Thanks Paul,

I also thought this was strange and only believed it after removing all other wires and triple checking.

Chalk it up to close proximity to tomorrow being 12:13:14.

Richard