well. there is a particular issue with stm32sprog which has massively hindered progress over the past few weeks. it's very simple: when uploading and running a program using stm32sprog, if it has interrupt service routines it is guaranteed to crash. however if you then set BOOT0 to 0 and do a RESET, the program will work absolutely fine [assuming it's coded correctly]
this simple little thing has prevented progress over the past couple of weeks because it has been impossible to distinguish "code incorrectly written" from "code that crashed due to stm32sprog".
dozens of examples and bits of code that _should_ have worked - DMA, ADC, DAC, Timers - will and can now all be revisited.
patience, patience...
... anyway i'm currently tracking how to get timers to update from an external gpio pin, and from there to fire DMA. it _is_ possible... just.... requires a huge amount of careful reading and research just to come up with only 30 lines of code that connect all the dots together without connecting any of the thousands of other options.
i think... to be absolutely honest, if i had known that the STM32F was so comprehensive / complex i would have said "sod it" and used a low-cost FPGA instead. but, hey, this is kinda hair-raisingly fun....
l.