I had one Tympan user ask about logging data to the SD card along with some sort of real-world timestamp. To do that, one needs to activate the real-time clock (RTC).
The Teensy 3.6 (the processor at the heart of the Tympan) has almost all of the elements needed to do the Real Time Clock. It just needs power that continues despite flicking the Tympan’s power switch to off. It needs continuous power. It doesn’t need much power (a coin cell battery is sufficient), but it does need power continuously.
Not wanting to add a coin cell to the Tympan, I did a little experimentation and found that, with two resistors and a piece of wire, I can power the RTC using the Tympan’s LiPo battery. I was surprised at how easy it was!
If you don’t want to read the full blog post above, the summary of the mod is shown below: