Max32 pin voltages - Negative Voltages???

Created Thu, 16 Aug 2012 00:50:53 +0000 by alvesjc

alvesjc

Thu, 16 Aug 2012 00:50:53 +0000

Hi there.

While working to port the existing analogWrite function to a 16 bit resolution version, I've faced a sittuation not really expected.

While measuring the PWM pin voltage while the program sweeps the pwm, I've noticed that the 0 voltage is in fact a negative voltage of around -100mV, and the full pwm voltage of 3.155V.

I thought this could be because I've messed with the timers, so i attached the multimeter to pin 2 and tested with logical 0 and logical 1. The results were -99mV for logical 0, and 3.192V for logical 1.

Is this normal??? Should the Max32 output a negative voltage?

majenko

Thu, 16 Aug 2012 09:00:24 +0000

No, that is not normal.

The MAX32 cannot output "negative" voltages. But then, "negative" is only with respect to where you are measuring "from".

What are you using as your ground point for taking the measurements?

Have you confirmed that your measuring device isn't giving results offset by a hundred mV or so?

alvesjc

Thu, 16 Aug 2012 22:52:24 +0000

Hi.

I'm measuring from ground in breadboard that is connected to chipkit ground.

I'll repeat measurments directly to chipkit ground.

alvesjc

Thu, 16 Aug 2012 23:03:39 +0000

Ok, my bad....

Bad quality breadboard...

This one will go to trash...

PWM is working fine, levels are normal.

Thank you about the reminder! ;)

BR,

Joao