Cephalotus said:
Maybe some "pre controllers" could work that are designed to give a signal output from ~0V to~5V depending on several input factors incl brakes, throttle, PAS, etc...
Sure, you could build one, if you know how to either design opamp circuits or program MCUs.
Realistically it's a lot easier (and likely cheaper than all the development costs) to just buy a Cycle Analyst v3 and set it up for what you want (although it does not do *everything* the way I personally need it to, it works for most people that use it for this).
I've been thinking for a while about a simple hardware circuit that would take pulses from a common cadence sensor and integrate them into a "constant" voltage output, with a simple adjustment knob for min throttle voltage out, and another for max throttle voltage out, and a simple gain knob to let you set it up for your particular cadence vs throttle output. It shouldn't take more than $10 in parts including a bit of perfboard to wire it on, or perhaps $15 or so if a PCB was made for it in enough quantity to make them cheap.
A bit more complexity would allow a brake cutoff input to shutdown the throttle output.
A bit more complexity from there would allow the use of some torque sensors instead of just cadence.
But this kind of system is so simple it's not really that tunable to a particular usage scenario, unlike the CA, unless you make even more complexity to the circuitry and more adjustment knobs. Very much of this and it gets a bit on the large side, and becomes cheaper and easier (especially for the end user) to do this using an MCU, programmed for the task. At that point, it's easier to just use the CA3, unless it simply doesn't have the feature(s) you need.
The mmc-3 is quite expensive, too, but you do not need that huge CA3 on your handlebar.
You don't "need" the CA on your handlebar at all.
You can mount it wherever you like, once configured (which can all be done via the USB-serial cable and the Windows or Apple setup program). Stick it in with the battery or the controller, or wherever else you like.
If you don't ever want to see the display on it at all, and don't mind some DIY, you can even take it out of the case and cut the LCD off, and have a smaller board you can package however you like.
If you like you can still even use remote buttons, switch, or knob via the Aux input, where the buttons/switch/knob is mounted whereever you can reach them, to change certain things on the CA "live", like switching presets, or amount of assist, etc.