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Nano GPIO pin 38 pre UserMain()
Posted: Wed Jul 29, 2015 7:43 am
by conk
After power is applied and
Before UserMain() runs and inits GPIO pin 38 to 0,
we are seeing pin 38 go high. Is there a way to control the reset value
pin 38 defaults to pre user program execution?
Using Pin 38 as GPIO output.
Re: Nano GPIO pin 38 pre UserMain()
Posted: Wed Jul 29, 2015 9:24 am
by rnixon
Not sure about the nano, but many processors now have "weak pullups" to help define a state instead of just being a high impedance input that flops around. Since you need this to be in a certain state during power up and power down, do you have a pull down resistor (10k?). I don't think you can ever rely on a processor keeping a certain state during either power condition since it will lose control at some point.
Re: Nano GPIO pin 38 pre UserMain()
Posted: Wed Jul 29, 2015 12:37 pm
by conk
Thank you for your response.
We do not have a pull down resistor on pin 38. Pin 38 is tied to a level shifting isolator IC and then to a relay. The relay is closing on startup due to the GPIO pin going high on power up before the UserMain()
starts.