I have gotten a few requests for an expansion board to accompany the Replicape lately, so I have made an inital version for anyone interested in adding more extruders than the standard two present on Replicape.
The Reach board uses the spare PWM and ADC pins from Replicape to keep the cost down and the software changes to a minimum. Reach adds three more high power mosfets controlled by PWM, three low power mosfets controlled by PWM for extra fans (12V) , three more thermistor inputs, and three stepper motors all individually programmable down to 1/32 step and with programmable drive current, just like on the motherboard.
The trade-off is that there are no longer any available pins for backlight, resistive touch or buttons for an LCD3 cape to stack on top. For this reason, the 46-pin headers are not stacking. If you want to use a display, you need to use the HDMI and USB host ports on the BeagleBone Black, for instance by adding a Manga Screen (Kickstarter coming soon).
The first "batch" will only be some 5 boards for prototyping and testing the design. As always, anyone is free to make their own version, but unless you are in a big hurry to try it, I suggest you wait for my own review before trying it. The Rev A0-boards have a tendency to need updating.. : )
I'll leave the design simmering a few days before sending it in. If anyone has any comments, feel free to add them and I'll try to defend my design choices or make changes if I do not have an answer.
The design-files and gerbers are here: https://bitbucket.org/intelligentagent/replicape