This is a special stopwatch to measure time from a "start-event" to an "end-event".
Using a normal button, the user activates the stopwatch and sets a given "start" GPIO to high. It then monitors an "end" GPIO for an interrupt and stops the watch as soon as the GPIO changes to low.
The main rationale for this project was to measure boot-times of a second Pi from power on up to the timepoint when an application program starts. In this scenario, the "start" GPIO is connected to an enable-pin of the power-supply of the second Pi. This could be a bucket-converter, an usb-powerswitch, or maybe a wide-input shim from Pimoroni giving power to the Pi. Once started, the application provides the end-event by pulling a GPIO to low.
The setup uses the following hardware-components:
- Pi-Zero
- one normal button for "Start"
- one normal button for "Reset"
- one mini-oled display
- one active buzzer
- some jumper-wires
Run
git clone https://github.com/bablokb/pi-stopwatch.git
cd pi-stopwatch
sudo tools/install
To install the software and some prerequisite packages. This will also enable a systemd-service so that the service starts at boot-time.