Morpheus-STM32 (work in progress)

A cheap 3D printer controller board for use with a "Blue Pill" STM32F1 generic board. Inspired on http://reprap.org/wiki/SinapTec

Design goals:

Follow the KISS Principle
Low cost
Single layer copper board
DIY-able (easy to make via toner transfer)
Only through-hole components
The very basic a printer would need
- Keep bed circuit separated/optional (if you are making a PLA only printer without a heated bed, you don't need to populate the bed circuit zone)
Open Source Hardware, made in Open Source Software

4 Pololu-like steppers (X, Y, Z, E0)
3 mosfets (Hotend heater, print cooling fan and bed heater)
3 MIN endstops (X, Y, Z)
Z Probe pin (in case you are building a delta printer and need the extra endstop)
2 thermistors (for E0 and bed)
2 12V fan connectors
I2C and SPI header

All logic voltage in this board is 3.3V. Do not connect 5V logic addons/devices without proper level adapting.
~~This board has no reverse current protection,~~ it has a diode to short-circuit and protect the board in case of reverse current, but if you connect power incorrectly you'll still damage components and/or your power supply (there's also a risk of caching fire, so please be careful).
This board has no overcurrent protection, please use a fuse on power input (e.g. auto-blade or inline fuse holder), recommended values are of 5A for the main board and 10A for the bed circuit.
Check all connections before plugging power.
Now for real, check connections...

Usually, "blue pill" boards have a wrong R10 value (USB pullpup resistor, should be 1.5k but manufcturers place a 10k or other value resistor instead), so you can add a 1.8k in R13. If your board has the correct value or you already fixed it in the board, then leave R13 unpopulated.
~~Hotend sensor uses a 1k resistor pullup (R1). Anyway, if you're having trouble with finding (or creating) thermistor tables, just replace it with a 4.7k resistor and use the usual Marlin tables.~~ Now Marlin has configurable thermistors, you can use thermistor 1000 in configuration.h and choose pull-up, ressistance and beta values in configuration_adv.h