I keep seeing references to the LPC1768 as opposed to the LPC1769 that I know smoothieboard uses. What's the difference? Digikey lists identical specs for both ICs. Will the stock firmware work on the '68?

Easiest way to induce OCD and/or insanity:  set Eagle's DRC to warn you about every trace that isn't angled at a multiple of 45 degrees.  

I wanted to verify some expansion pin assignments, any help would be appreciated.  

The board I am working on is described here: https://plus.google.com/u/0/+RayKholodovsky/posts/YDwDF2Lk95j

I need to assign pins for the 6th stepper driver (3rd extruder) and a hobby servo as this is still a popular approach for probing.  

The pins I have available are P2.4 (psu.output_pin) and I think I will need to re purpose the 4 LED pins 1.18-1.21. 

Documentation does not specify: can a servo can be run on any IO pin, or would a PWM pin be needed/ preferable?  
Also an idea was brought up to do temperature sensing of the board in regard to monitoring the MOSFET temperature, I could easily add an SMD thermistor to the board and potentially use a temperatureswitch module to issue a kill/ pause+cooldown command if exceeding a set threshold.  
If so I can connect that to P1.30 (ADO4) and move glcd click button to one of the previously mentioned pins.

I should be all set on MOSFETs and 4 thermistors for bed + 3 hotends is all I need.

Thanks for the help!

I've had quite a few requests from folks to see the #Smoothiebrainz  derivative board that I've been working on.  Well, here is a preview of the work in progress: 
ReMix (Powered by Smoothie)

Tentatively, here's the functionality we're looking at:
6 stepstick sockets so you can pop A4988 or DRV8825  stepper drivers modules per your preference, and easily replace one if it burns out.  Great for triple extruders or Pick n Place machines with multiple heads.  Also, there's room for doubled up headers for dual Y CNCs, dual Z printer frames, or anything else without having to splice wires yourself. Or install a single screw terminal instead.  
1 huge MOSFET to run your heatbed.  Tens of amps is possible, it's theoretically rated for over 50, I've run 20 amps thru this thing on a different PCB using a 12v silicone heater, it got hot but kept on pushing.  More via stitching and a straight shot to an entire ground plane for better heatsinking on this board.  
4 standard MOSFETs for 3 Hotends and a print cooling fan, or other general IO.  These guys are rated for over 10 amps each, so they won't even break a sweat running your cartridge heaters.  I'm also looking to add another few smaller MOSFETs for accessories such as a hotend cooling fan (like for E3Ds) and lighting, but space is getting tight. 
Reverse biased endstop circuits so you can run a simple mechanical endstop at 5v or an inductive sensor at 24v without worry.  
Connectors for directly hooking up a Graphic LCD controller. 
Everything else smoothie has to offer: microSD card slot, USB, and I'm currently grappling with getting an ethernet jack on board. 
All in a 100x100mm PCB and at a very competitive price for the feature set this offers.  And also Wifi!  Going to put an ESP8266 module onto this board for wireless control.  

I'd like to ask the community for help with reviewing the design and offering any and all feedback/ suggestions, I think it would be good to get some initial dialog going before I get too deep into routing.  Obviously the routing (all by hand, as it should be) is nowhere near complete. 

Eagle files are in my github, in the v0.3 folder: https://github.com/raykholo/Smoothiebrainz

Thank you all

I've got a 300w DC Spindle with basic speed controller with potentiometer (the standard things you'd find on a 3040 frame) and I want to start tapping holes in milled plates as an operation.  So.  Are these spindles reversible?  I've been told that it's a basic dc motor so there shouldn't be a problem just flipping the polarity of the 2 wires.  
So, in that case I can make an H bridge between the output of the speed controller and the spindle using automotive relays to keep everything electrically isolated.  The relays I have are rated for at least 30 amps and I'll be running everything on 24v (have we been keeping count over how many times people have told me to switch to 24v?) so there should be plenty of room.
I also think it might be cool to get an actual drill chuck mounted as an ER11 presents the challenge of swapping out the collet every time I want to change to a different size tap, but that's a problem for another day.  
Thoughts?  

I ordered Cohesion3D ReMix PCBs this weekend. And I got a bunch more parts in this morning so here's a more complete layout test. Print Eagle + cardboard for the win!

Just finished routing my Cohesion3D ReMix (Powered by Smoothie) board. Man this is tight.  Down to 8 mil traces with 6 mil clearance in between them.  I still have redo the last 4 stepper drivers per the new routing pattern you see in the first 2, and spend an inordinate amount of time seeing if I can squeeze in a servo header for a leveling probe, but other than that, it's time for some community review!  Please take a look, the eagle files are in my github, and let me know what you think:  https://github.com/raykholo/Smoothiebrainz/
I also added some new features:  there is an onboard thermistor near the MOSFETs to monitor if they get too hot (keep in mind these things will burn you long before they exceed the temperature they are rated for) and a number of responses can be scripted.  Remind you of anything?  High end PC motherboards perhaps?  
There's also footprints for flyback diodes so you can quickly install these if you need to run electromechanical devices (like relays or the pumps and solenoids you'd find on a Pick n Place) without having to get "creative" with your diode installation.   
Finally, I did manage to squeeze in that 6th MOSFET and this one is selectable between your motor voltage and 5v, so you can run a larger variety of small accessories from it. 
I'd keep going, but with 6 stepper drivers and MOSFETs along with WiFi in a 100mm square board, there's not even space for air in between the components :)

Proudly introducing the Juki Nozzle Holder (capable of automatic tool changes) for Pick n Place machines.  We're reverse engineered and improved upon this part which costs over $100 from China and are getting a higher quality, more precise version made right here in the USA for only $40 each + $5 domestic shipping.  

A full description is here: https://groups.google.com/forum/#!topic/openpnp/82hIAKQZnr0
and a video intro is here:  https://youtu.be/Rm-aIyV9Cko

If you or anyone you know is interested in diving into the wondrous world of Printed Circuit Board assembly, take a look and pass it along!

I've had quite a few requests from folks to see the  #Smoothiebrainz  derivative board that I've been working on.  Well, here is a preview of the work in progress: 
ReMix (Powered by Smoothie)

Tentatively, here's the functionality we're looking at:
6 stepstick sockets so you can pop A4988 or DRV8825 stepper drivers modules per your preference, and easily replace one if it burns out.  Great for triple extruders or Pick n Place machines with multiple heads.  Also, there's room for doubled up headers for dual Y CNCs, dual Z printer frames, or anything else without having to splice wires yourself. Or install a single screw terminal instead.  
1 huge MOSFET to run your heatbed.  Tens of amps is possible, it's theoretically rated for over 50, I've run 20 amps thru this thing on a different PCB using a 12v silicone heater, it got hot but kept on pushing.  More via stitching and a straight shot to an entire ground plane for better heatsinking on this board.  
4 standard MOSFETs for 3 Hotends and a print cooling fan, or other general IO.  These guys are rated for over 10 amps each, so they won't even break a sweat running your cartridge heaters.  I'm also looking to add another few smaller MOSFETs for accessories such as a hotend cooling fan (like for E3Ds) and lighting, but space is getting tight. 
Reverse biased endstop circuits so you can run a simple mechanical endstop at 5v or an inductive sensor at 24v without worry.  
Connectors for directly hooking up a Graphic LCD controller. 
Everything else smoothie has to offer: microSD card slot, USB, and I'm currently grappling with getting an ethernet jack on board. 
All in a 100x100mm PCB and at a very competitive price for the feature set this offers.  And also Wifi!  Going to put an ESP8266 module onto this board for wireless control.  

I'd like to ask the community for help with reviewing the design and offering any and all feedback/ suggestions, I think it would be good to get some initial dialog going before I get too deep into routing.  Obviously the routing (all by hand, as it should be) is nowhere near complete. 

Eagle files are in my github, in the v0.3 folder: https://github.com/raykholo/Smoothiebrainz

Thank you all

Smoothiebrainz Update #2:
Just got a board working!  It lights up (in a good way), it was recognized on the computer, and I was able to flash the bootloader successfully over serial!  Next step will be loading the firmware itself over an SD card.  More to come soon!  Thanks for the patience.  It took a lot of work (and rework) to get this board working.