I have one of these $20 DSO's with a stm32f103c8t6, it might have been sold as with 50-100-200kHz BW. The only other chip on it is an op-amp. But I damaged the MCU years ago when soldering it. I got some new chips, but forget there's no external memory chip, so all the program must have been on the chip.
The PCB had connections for UART, and I2C or something similar, and a USB header. So I'm assuming the firmware could be updated.
But in that case, can I put a blank chip on the PCB, and somehow upload the whole program ? (if I find it online).
Otherwise, I can put the chip on a breakout board and try something that way. I do have an Arduino and a BusPirate, but I don't know much programming yet (but I've done some).
I do want one of these mini, 9V DSO's, besides the low bandwidth, they are as portable as a handheld DMM. If I wanted to, I could remake just about any of the ebay ones on a protoboard, and use and open program for it. Everything for the little LCD screen is on another PCB with headers, just waiting for MCU instructions. I guess all that LCD stuff is open source and out there to find.
How much is there to these mini-DSO programs tho ? For a real 50/100/200kHz BW, what might they compare to in size and complexity ? How many pages of code might these be ?
Again, this one only had 1 MCU, 1 quad op-amp, and the all-in-one LCD section. So it takes a bunch of samples, does some DSP in the chip, then outputs to the screen. And has some buttons for basic DSO settings like zoom and coupling.