Hi!
I would say a proper schematic capture will take at least 10 hours, rewriting the STM firmware after one has the full schematic and protocol to be implemented fully specified, it's realistic to have it in beta after 90 hours.
I think that's a reasonable, possibly even conservative, estimate of the time needed to produce a good set of Schematic Diagrams!
I admit, as I said in a previous post, that I'm not skilled in reversing firmware or communication protocols in a given piece of unknown equipment, but I can use Member DC1MC's estimate of how long the drawing–out will take as a guide and compare how long I take with the ten hours estimated!
(I think it wouldn't be a wasted effort for more than one of us to work on the schematics as with a densly–populated analogue/digital surface–mount PCB like this it's so easy to get it wrong somewhere, which would affect the FW reversal!)
My suggestion for new firmware would be:–
1) Find out what type of LCD driver is needed for the original display and design a good U.I (No horrible Chinese Lettering!) – Our Continental Friends may be able to assist with translations for additional languages if needed;
2) Find out how many functions need to be sent back to the main PCB for control of the Altera Cyclone;
(Waveform type selection, amplitude, frequency, phase, DC offset etc., per channel, plus one function for each Arbitrary Waveform provided – it may be possible to use the PC software provided by FeelTech to get the waveform–function for each Arbitrary Waveform provided;
3) Decide on implementation of the additional control functions – AM/FM Mod, VCF, Sync, etc;
4) Consider wether a Frequency Counter Function is needed;
5) Finally, the "housekeeping" functions – factory reset, Cal/setup, self–test, firmware-update, etc;
I certainly agree it's not trivial but I thought if I set out a rough draft of the firmware functions first it'll assist those excellent chaps on here who are much more "au–fait" with software/firmware engineering than I am!
Chris Williams