I recently ordered a second batch, made by WeAct with USB-C connector.
Ignoring the black PCB versions of the STM32F103 "blue pill", I have noted that there is a vast variety of boards based on F4xx chips. They all seem to be based on a Cortex-M4 (whereas the F103 is a Cortex-M3). What I read is that these are identical except that the M4 includes SIMD instructions aimed at DSP applications.
All of the black pill boards seem to sell for about $5. Some have a micro-USB connector, but it seems that most these days have a USB-C connector. Some have 40 pins on a side, others have 38, but offer mounting holes.
F103 72 Mhz 20K ram, 64K of flash F401 84 Mhz 64K ram, 256K of flash F411 100 Mhz 128K ram, 512K of flashNote that the letters after the F411 are important. The above are F411CEU6 parts. If you look at an ST datasheet you will see that different letters can indicate different amounts of ram and flash.
There are also nicely priced boards in a different shape with:
F405 168 Mhz 192K ram, 1M flash F412 100 Mhz 256K ram, 512K flash F446 180 Mhz 128K ram, 512K flash G474 170 Mhz 128K ram, 512K flashOf these, the F412 interests me because of the greater RAM.
Also there are a series of AT32 (not STM32) parts with similar numbers such as AT32F403. The offer higher clock speeds (240Mhz). What about documentation? AT is apparently "Artery" -- proceed with caution!
Tom's Computer Info / tom@mmto.org