Hi all,
I am trying to figure out how to interface with a switch in an external circuit. Normally I'd connect the pin to +V with a pull-up resistor and connect the switch to ground, so it's logic 1 when the switch is open and logic 0 when closed; however, the circuit I'm trying to connect to has its own 15k resistor, so when the switch is closed the voltage only drops by ~30mV; obviously still logic 1. How exactly am I supposed to interface to this?
This is the circuit I am testing with on my breadboard. Components R3 and to the right are in the external circuit and can't be changed.
This is the schematic for the external circuit. Follow the PTT line to ground.
Thanks.
I am trying to figure out how to interface with a switch in an external circuit. Normally I'd connect the pin to +V with a pull-up resistor and connect the switch to ground, so it's logic 1 when the switch is open and logic 0 when closed; however, the circuit I'm trying to connect to has its own 15k resistor, so when the switch is closed the voltage only drops by ~30mV; obviously still logic 1. How exactly am I supposed to interface to this?
This is the circuit I am testing with on my breadboard. Components R3 and to the right are in the external circuit and can't be changed.
This is the schematic for the external circuit. Follow the PTT line to ground.
Thanks.