Hi I’m new here and I realise this an old thread - nevertheless for the sake of adding to the stock of solutions to this problem (and since there are obviously still people like myself out there who have been trying to find one), I have another work around which doesn’t involve soldering up new connectors etc. Dependent on owning a drum machine or something similar that emits a 5v pulse trigger - it is possible to simply run a trigger from 808/rd8 etc into the trigger in of a CS (in my case CS5) whilst running CV pitch from Keystep into CV in of the CS5 (KS needs to synced out from the RD8 and slaved to its analogue clock). What slowed me down for ages was not realising that the Keystep can be switched to Hz/V mode using the Arturia midi centre software.
There are a handful of compromises with this naturally, you can’t ‘play’ the CS5 in real time using the Keystep as it’s not triggering anything but if you simply want to sequence - it’s great (for writing in basic sequences it’s not after all absolutely necessary to ‘hear’ the notes as you input them, and if you really do need to - you can simply tap the trigger button on your drum machine for each note as you go - sounds inconvenient but it’s nothing really). You get full access to the entire CS octave range (unlike using an SQ1 for example), you can transpose sequences using the Keystep, and, you can play around with existing sequences by changing the trigger pattern on the RD8 (cowbell, hand clap or accent). Everything is synced and plays from one tap of the RD8 and apart from Portamento, all parameters appear to work as normal on the CS5. Also problem with CS not recognising rests and playing a constant tone in between sequences notes is solved providing you ensure that drum trigger pattern corresponds to KS sequencer pattern!
So, to cut a long story short - if you are looking for a simple way to wake a CS up to sequencing - and integrate it into a clocked system - this seems to be it - KS controls pitch - RD8 controls trigger. Was miraculous when it suddenly started working after days of fiddling around. A supremely satisfying moment!