Verifying time delays

Syntalos does an excellent job at keeping devices synchronized and at keeping times, but verifying that is better than just believing it! Verifying time synchronization is also also a good regression test to ensure no code or environment change has altered Syntalos’ behavior, and a good test to find any inherent latencies in the system that can be corrected as fixed errors in postprocessing.

Since buying a commercial pulse generator can be expensive, we’ve created a small Raspberry Pi Pico-based device that can be built cheaply and used as test pulse generator.

Pi Pico Pulse Generator Hardware

You will need to acquire the following components:

You can fairly easily assemble these components like this:

It is recommended to put the LED on a wire, or even better, a BNC connector, so it can be moved away from the signal generator. The wire will also allow for splitting the electrical signal to feed into other devices.

This is how the final result may look like, in a box:

Pi Pico Pulse Generator Firmware

You can now download the prebuilt firmware for the Pico pulse generator and upload it to the device, or build it yourself. To build it yourself, clone the Syntalos source code and use cmake for building the files from contrib/testpulse-generator:

git clone --depth 1 https://github.com/bothlab/syntalos.git
cd syntalos/contrib/testpulse-generator
mkdir build && cd build
cmake -DPICO_SDK_FETCH_FROM_GIT=ON ..
make

This will generate a syntalos-testpulse-generator.uf2 file in contrib/testpulse-generator/build, which you can then upload to your Pico to make it generate precise(ish) pulses as external control clock.

The switch on the device can be used to select one of two modes, depending on which position it is in when the device is powered on. It can either operate in fixed-interval pulses, or vary the pulse interval.

Syntalos Measurement

There are two types of time synchronization measurement tests that you can perform: Long-running measurements to check whether the device times remain aligned for very long measurements ("Marathon Sync Test"), and short measurements of many experiments where they are continuously started and stopped to determine if the initial time offset between devices is small and constant ("LaunchSync Offset Test").

Marathon Sync Test

TODO Coming soon!

LaunchSync Offset Test

TODO Coming soon!