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Panda II: Please help me understand the "MOD" Pin


#1

I have read whatever I can find related to the MOD pin, because from what I have observed the system behaves strangely when it has been grounded.

For example, If the mod pin is grounded and I don’t instance any USBClient controller code it appears that none of my code is executed. Please explain that behavior. Why does it just lock everything up?

Also, is it possible to change client controller mode? For example, is it possible to starts CDC and then later chance to CDC_WithDebugging without rebooting?


#2

If you switch to serial debugging then the serial pins can’t be left floating.


#3

Thanks Gus,

Any thoughts on my first question:

“For example, If the mod pin is grounded and I don’t instance any USBClient controller code it appears that none of my code is executed. Please explain that behavior. Why does it just lock everything up?”


#4

Can you describe how you proved that ?


#5

Brett,

I have not proved anything, but this is what I have experienced.

If I ground the mod pin and don’t instance or start any usbclient code (i.e. Mass storage, CDC, etc) then Panda does nothing… I can’t blink lights, nothing. It basically locks up.

Its really strange, I don’t quite understand why it would behave in that manner.


#6

OK, so show us your sample code, and explain why you believe that the app isn’t starting. Eliminate everything in your code but the simplest repro for this.

As Gus says, if you use the MODE pin to set serial debug, then you can’t leave the serial pin float. How have you addressed that?