I have two picos each having a separate power source e.g. usb. There is a wire going from the ground of one to the ground of the second.
One is the "main" pico and the other is the "control" pico. There is a second wire going from a gpio output of the control pico to the run pin
of the main pico. The wires are about 20 cm long. The problem is to make sure that if the main pico is powered on that plugging and
unplugging the usb power of the control pico will not reboot the main pico. You can also plug or unplug the usb power of the main pico at any point hopefully. There is a 4.7k pull up resistor on the run pin. The problem is also to prevent any current from the run pin flowing back into the control pico when it is powered off. google ai mentioned some complicated stuff about parasitic impedance. I was just trying to find the thevenin impedance of the control gpio pin when the pico has no power (but still grounded).
the control pico runs a circuitpython script that creates a digital pin and sets it high then reads tty input for a request to reboot the main pico.
It is a simple pico probe. When it does it sets the wire low for 4 seconds then high again.
I am not that experienced. I expect the control gpio out will be floating until the digital pin is created and then stay high even when the control pico program stops if the pico has a software reset.
Someone mentioned using a tristate buffer but I thought you could use two in series otherwise what would you connect the enable pins to?
You need the Vcc and enable pin from the first buffer hooked up the the first pico circuit and the same for the second buffer hooked up to the 2nd pico circuit. If you power the buffer from the opposite pico's circuit you would have to assume it was plugged in.
One is the "main" pico and the other is the "control" pico. There is a second wire going from a gpio output of the control pico to the run pin
of the main pico. The wires are about 20 cm long. The problem is to make sure that if the main pico is powered on that plugging and
unplugging the usb power of the control pico will not reboot the main pico. You can also plug or unplug the usb power of the main pico at any point hopefully. There is a 4.7k pull up resistor on the run pin. The problem is also to prevent any current from the run pin flowing back into the control pico when it is powered off. google ai mentioned some complicated stuff about parasitic impedance. I was just trying to find the thevenin impedance of the control gpio pin when the pico has no power (but still grounded).
the control pico runs a circuitpython script that creates a digital pin and sets it high then reads tty input for a request to reboot the main pico.
It is a simple pico probe. When it does it sets the wire low for 4 seconds then high again.
I am not that experienced. I expect the control gpio out will be floating until the digital pin is created and then stay high even when the control pico program stops if the pico has a software reset.
Someone mentioned using a tristate buffer but I thought you could use two in series otherwise what would you connect the enable pins to?
You need the Vcc and enable pin from the first buffer hooked up the the first pico circuit and the same for the second buffer hooked up to the 2nd pico circuit. If you power the buffer from the opposite pico's circuit you would have to assume it was plugged in.
Statistics: Posted by garberw — Sun Jun 08, 2025 4:29 am