DIY midi to cv module based on Midimuso CV12 kit

I'm currently in the process of building a big modular synth, using some ICs from my defunct Yamaha CS15D synth, at some stage I'm planning on adding a midi to cv converter module to it so I can connect it up to a midi controller keyboard, or an audio interface that has midi connectivity, anyway, I was wondering how I go about getting one of these Midimuso CV12 kits, how much do they cost?

A few years late for this discussion.

I wrote to Robert Cottam of Midimuso and have pasted his reply to my questions here
TLDR: not interested in modifying the firmware, unless paid for his time. 5v is enough to run the main chip but too little for others, so voltages will be wrong. 9v is ok but some inaccuracies result. Best approach is clamp output to 5v as discussed above and run off 12v (so, better as a separate box than as a module in an AE system).
> info@midimuso.co.uk
> Attachments30 Aug 2022, 21:59 (8 hours ago)
>
>
> Hi Rodney,
>
> Could CV-12 run happily with a 5v supply instead of 12v with no or
> minor modifications?
> The 5V is used by the microcontroller so it would be happy BUT
> The LM317 would drop 1.2V giving output voltages of 0V to 3.8V so you'd
> have a weird 0.36 volts / octave scenario.
>
> If not 5v, would 9v be enough? (the standard Master module takes 9v
> in then converts it down to 5v for the bus, so I could run a >separate
> wire to the CV-12 if needed
> The LM324 op amps would be happy with 9V and the uController would get
> its 5V from the 7805.
> The LM317 would drop 1.2 volts to give 7.8 volts and this could be
> tweaked down with the trimmer to 5.3V to give a 0.5 volts / octave
> scheme whereas the AE is 1V / octave so it wouldn't work.
>
> The CV-12 docs say to boost the 0-5v output up to 10v. If I want to
> use 0-5v instead, can that be adjusted without new firmware on your
> chip?
> No.
>
> The best solution would be to use the 9V as main power (instead of 12V)
> and for me to have the firmware altered so it produces 1V / octave from
> 0V to +5V but.....
> I'd have to charge for my time both in writing the code, testing it on a
> board and making sure none of the other functions have been altered.
> This would come to around £300.
>
> I think the best solution on the forum is the clamping one. If you can
> clamp the outputs to max 5V you are getting 1v / oct over 5 octaves.
> You'd still need the full 12 volts for power though.
>
> Best regards,
> Robert Cottam
> Director,
> Midimuso
> website: midimuso.co.uk