Program pin on Teensy 3.5 need pullup resistor ?

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Buzz

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I have a system that uses a Teensy 3.5 as the controller , I have hooked up an external switch for the Prog. pin to Ground , when I hook it up the Teensy does not boot up ??

I have pins in both the Prog and Reset , I did notice that IF I accidentally touch the Reset or Prog. pins it resets ! are these High impedance pins ??
I am going to try a 4.7k ohm Resistor to 3.3vdc on the PCB to see if that helps.
Anybody have this issue ?

Thanks
Buzz
 
Some measured voltages with and without the switch connected to the program pin would be useful here, since it certainly should not work like that.

Edit: Followed my own advice and dug out my T3.6 prototype (which may be different to your T3.5 but cannot find any of mine at the moment) and it looks like the program is very high Z With 100K across the button being a low enough resistance to pull it to ground and keep it in reset. Still unsure how your switch is able to do that in the open position but certainly if it is slightly leaky it looks like that can be a problem. Suspect this is part of the low power consumption design but do not have anything to back that up.
 
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Some measured voltages with and without the switch connected to the program pin would be useful here, since it certainly should not work like that.

Edit: Followed my own advice and dug out my T3.6 prototype (which may be different to your T3.5 but cannot find any of mine at the moment) and it looks like the program is very high Z With 100K across the button being a low enough resistance to pull it to ground and keep it in reset. Still unsure how your switch is able to do that in the open position but certainly if it is slightly leaky it looks like that can be a problem. Suspect this is part of the low power consumption design but do not have anything to back that up.

I will try that and try a 4.7k res. to 3.3 v to see if that helps , I have to make up a setup to test it later , THANKS !
 
Ok I used a 1k to 3.3v on the pcb and a .0047uf ( 4700pf) cap to ground that fixed it completely
 
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