Panda II PWM Output Issue

Archive
1

On the Panda II board, I am using all six PWM outputs. These outputs are driving a simple transistor circuit used to take the 3.3v swing of the PWM output to 5v. This works fine as long as I don’t connect the last PWM output to it’s circuit until after the system has booted.

Obviously, I ran into the fact that PWM #6 shares a secondary function (“MODE”). My circuit effectively is pulling down MODE and this is causing the system to go into the serial bootloader. I don’t want that, obviously, but am not sure how I design around it.

What I need is for the pin to be held high (or, not pulled down low) during the period of time the startup code samples the pin. Alternatively, if there is a way I can have the startup code ignore the MODE pin and always boot as if nothing was connected, that would work.

2

Add a pull up resistor?

3

Yes, but the question is if that will work. In order for a pull-up resistor to work, I would imagine that the PWM output would have to drive low. Maybe it does, but in the data sheet for the underlying processor, I can’t find any statement about how the PWM module of the chip actually is actually driven.

As always, I can just try it. But I would hope someone has run into this before and can give me some specific advice.