I want to exercise with a KiCad, so I decided to make a modification of a popular STM32 dev board, widely known as BluePill, as a hobby project.
What I want to add/replace:
- USB type C instead of microUSB
- replace the jumpers for boot options with button
- add power protection to USB against external power source (thinking between diode or mosfet connectivity)
- replace the 4-pin SWD interface with STDC14, as on latest STLink v3
- add the RTC power isolation
- replace the 8Mhz crystal with SMD like on MappleMini
This is my first “project from scratch” and is still Work In Progress.
The power supply is still under consideration (if I need the battery power or rechargeable power or just left as is). Currently, I’m more disturbed about connectivity for USB and programming interfaces.
- regarding if I should to connect the TX/RX from STDC14 to PA9/PA10 so I will be able re-programm locked microcontroller with UART using the same programming connector, or connect it to USB RX/TX.
- some schematics had wrong values for some pull-up resistors. I wonder if I fixed those correctly and didn’t miss anything else.
- The STDC14 connectivity in general. Is it correct or should be any extra wiring? I also want to have SWO pin on that connector. Found some info in datasheet and on StackOverflow and here
- If USB type C is connected properly? My reference
This is my current schematic:
Or, as PDF file:bluepill_reforged.pdf (104.4 KB)
P.S. The schematics of the original BluePill are:
schematics.PDF (179.5 KB)