STM32FxxxR

The board came about cause of a need to experiment with higher performance processors other then the one that comes on original Blue Pill and secondly we needed more I/O pins of what the C version boards have.  Secondly we needed peripherals from other processors for couple of the projects. Yes you can de-solder original processor from the board and replace it with one from other family of processors, however that is just a work around and its still required to purchase a Blue Pill board and alter it. Additionally we did not wanted the 32.768Khx crystal and there was no pins connected to those ports. Basically what we needed was a bare board to which a controller can be mounted with primary crystal and programming port.
One thing we wanted was a battery backup for onboard RAM and clock, however to keep the board size as small as possible so we decided to just have battery connection pin that we can connect a battery to and for the benefit to have battery on board for the odd time it did not make sense to make it that much larger. There are resistor dividers to monitor the battery where a solder jumper needs to be shorted to enable it.
The board has all of the pins routed to the 2 edges with swclk and swdio pins only available on the programming port.