In your response to Cerin’s query above you state that “when the switch is on, the voltage on the A pin will be partway between VIN and GND, so it is possible that your Arduino would not recognise that voltage as high.”
I have a similar situation but am using a Baby O instead of an Arduino.
The intention is as follows:
1) The first push of S1 (remote momentary push button) will:
a) Pull the Mini SV A pin to GND
b) Supply +9 VDC to the Baby O VIN
c) The Baby O will then run its sequencing program
d) On completion of the sequence the Baby O will send a pulsed output (via pin PD0) to the Mini SV OFF pin thus powering down the Baby O.
2) Should S1 be pushed a second time (whilst the sequencing program is running) the consequence will be:
a) The Mini SV will see this as a second initialisation command and do nothing as it is already supplying +9 VDC to the Baby O VIN.
b) The Baby O which is now running, will sense the second push of S1 (via pin PD1) and will stop the sequence, write to flash, then send a pulsed output (via pin PD0) to the Mini SV OFF pin thus powering down the Baby O.
My questions are:
a) Will the Baby O (pin PD1) be reliably pulled to GND on the second push of S1 given that S1 is simultaneously pulling to GND +9 VDC from the Mini SV pin A and +5 VDC from Baby O pin PD1, or will it see a voltage “partway between VIN and GND” ? (Please refer to attached diagram for clarity).
b) Given that the Mini SV supply will be +9 VDC (the lower end of its 4.5 to 40 V operating range) can I assume that its startup-state will be OFF after a battery change?
Mini SV Baby O Diagram.pdf (73.6 KB)