This Version of the Gen7 Electronics uses an extension board to add SD-card support

I stopped working on this project !
Please use the current version from Traumflug.

Status:

 * Printing works normal.(at least with my board)
 * communication with sd-card is unstable, printing from sd-card is not possible
   (maybe because the level conversation with resistors produce to many communication errors)

Design Goals:

 * PCB easily to manufacture on a RepRap.
 * All parts on one board. Except for the Opto Endstops, of course.
 * Enough components to run a Mendel or Huxley with extruder and heated bed.
 * Easy to set up. For example, this would include an USB port.
 * Well available and cheap parts.
 * Based on the ATmega644.
 * Well suited for community driven development. 

Features:

 * Single board solution.
 * Single sided PCB.
 * Pololu stepper drivers, exchangeable. // may change to bigger through hole stepper drivers from Toshiba to reduce cost and improve heat management
 * 4x stepper motor drivers with 1/16 microstepping.
 * printing from microSD-Card
 * TODO: on-board USB-RS232 converter.
 * Integrated hardware for driving one extruder (stepper, heater and thermistor).
 * Integrated hardware for a heated bed (heater, thermistor).
 * Ready to be hooked up on a generic PC power supply unit (PSU).
 * Use of standard connectors.
 * Debug LEDs for power and both heater outputs.
 * Can turn PSU on and off in software.
 * Reset button. 

###################################################################################

						          ATMega644P

                                  +---\/---+
x_min                 (D 0) PB0  1|        |40  PA0 (AI 0 / D31)   temp-1
y_min                 (D 1) PB1  2|        |39  PA1 (AI 1 / D30)   temp-2
z_min            INT2 (D 2) PB2  3|        |38  PA2 (AI 2 / D29)   step-1
heater-2          PWM (D 3) PB3  4|        |37  PA3 (AI 3 / D28)   dir-1
heater-1          PWM (D 4) PB4  5|        |36  PA4 (AI 4 / D27)   enable-1
                 MOSI (D 5) PB5  6|        |35  PA5 (AI 5 / D26)   step-2
                 MISO (D 6) PB6  7|        |34  PA6 (AI 6 / D25)   dir-2
                  SCK (D 7) PB7  8|        |33  PA7 (AI 7 / D24)   enable-234
                            RST  9|        |32  AREF
                            VCC 10|        |31  GND 
                            GND 11|        |30  AVCC
                          XTAL2 12|        |29  PC7 (D 23)         step-3
                          XTAL1 13|        |28  PC6 (D 22)         dir-3
                 RX0 (D 8)  PD0 14|        |27  PC5 (D 21) TDI     step-4
                 TX0 (D 9)  PD1 15|        |26  PC4 (D 20) TDO     dir-4
SD-enable   INT0 RX1 (D 10) PD2 16|        |25  PC3 (D 19) TMS
            INT1 TX1 (D 11) PD3 17|        |24  PC2 (D 18) TCK
                 PWM (D 12) PD4 18|        |23  PC1 (D 17) SDA
                 PWM (D 13) PD5 19|        |22  PC0 (D 16) SCL
                 PWM (D 14) PD6 20|        |21  PD7 (D 15) PWM     PS on/off
                                  +--------+

###################################################################################


For more details, see http://reprap.org/wiki/Generation_7_Electronics