The default firmware, on the other hand, is barely adequate. It does all the basic stuff, but is not very well coded. The device has storage places for up to 4 applications, so you can add custom programs without overwriting the main interface. As I had previously familiarized myself to the cheap STM32 Discovery board, programming for the DSO Quad seems quite easy.
NOTE: The later DSO Quad hardware revisions have switched the flash (and maybe the FPGA?) chips. I do not have the new hardware, so I cannot say whether any of this will work for new DSO Quads.
To ease frequency response measurements on audio stuff, I wrote a program using the integrated DAC on the DSO Quad.
This logic analyzer application is my second custom program for the DSO Quad. The device has buffer space for 4096 samples by default, which is enough for analog work but somewhat limiting with digital signals. Furthermore, the default firmware makes browsing cumbersome by not letting you change the timebase when the capture is paused.
Huh, it was quite a crunch. For the past 3 months, I've been working on implementing a Pawn interpreter for the DSO Quad. This should make application programming simple enough.
I have mentioned before that the protection diode D5 on the DSO Quad's digital channels is poorly chosen. It has 5 V threshold voltage, and also awfully high capacitance. The capacitance ruins the digital bandwidth, and the high threshold voltage means that it doesn't really protect much anything.