There is a cheap, wildly available STTM3232F103C8T6 board out there. Because of it's shape and color it's called Blue Pill (BP). More details about this board can be found on jeelabs. There are at least two slightly different boards out there. This extension board is designed to match the BPs where the 2x03 pin header is next to B11, B10 and B1. These are the boards where the USB connector is mounted in a cutout on the PCB. Other boards do have the USB connecter on top of the PCB and this 2x03 header is offset one pin – these boards will not fit nicely and need creative soldering as shown here.
The BP fits perfectly fine in a breadboard but it's missing the convenient programming headers for SER+ and some other features (see list below).
Thanks to the fantastic people over at jeelabs.org I was able to create this add-on board for the Blue Pill in KiCAD. This is how it will look like mounted on a BP.
- Programming header for programming the BP using a SER+ - including automatic reset of the target (BP)
- Area for mounting an RFM69-CW module
- Reset button
- Optimized for use on a breadboard
Revision 1 is a little bit off-center but working perfectly fine.
There are some plans for the next revision of the board (see Issues). Some of them will probably become a completely different board as this one is meant to be used on a breadboard.
The Blue Pill Extender (BPE) is mounted on top of an existing BP (label facing up). Make sure you solder the headers facing down to the BP first so it will fit into a breadboard before continuing here.
First prepare the BPE by soldering on the small resistors. The reset button is not required but may be helpful. Also add the RF module if you plan to use one. Make sure the RF module is not placed wrongly!
The 90° programming headers should be mounted from below (soldering on top) but they do work both ways.
Now remove the jumpers from the BOOT? pins on the BP and push the BPE on there. Make sure the 2x3 header of the BOOT? goes through the BPE and there there is still enough room to plug in an USB cable. Solder the 2x3 headers to the BPE. Now use some short wires (or leftover resistor legs) to connect all the outer BPE pins to the corresponding pins on the BP below – DO NOT solder the antenna to the BP below!