It all started with the idea of a PCB which could display the time in BCD code and is small enough to wear it on the wrist. Sadly i was not able to find a Housing which could be used for the Clock, so i created one myself in OpenSCAD and 3D-printed it. After a while i got tired to explain the BCD code to everybody, so there is also a Analogish Version available.
The Software for both Versions is unified and just differentiated by the Linker. So there is no change to the Code needed.
After some problems with sweat entering the Housing and destroying the electronics, i tried
several possible solutions (read more in the story).
The alternative try to solve the sweat issue was to remove the buttons completely and replace them with a G-Force sensor. As sensor the Bosch BMA456 is used, since it features various interrupt functionalities to wakeup the microcontroller and only draws a few microamps in standby.
The powerful Sensor also made some other cool features for a wrist watch. There is a Wrist Tilt detection to activate the Watchface once the user rises the arm and takes a look on the watch. Now the watch can also be turned on while only using one hand e.g. while carrying stuff.
Another cool new feature is a stepcounter, so the watch is also a (not completely sweat resistant ;-) ) fitness tracker.
The next evolution step is switching to a new more powerful controller. For this the STM32L432K Controller was chosen. This controller also features a calender in the built in RTC.