1. Mounting Holes (4 holes). This mounting hole location (upper left corner) is connected to GROUND.
2. STM32F103 "Blue Pill" Module. This is the header for Firmware Programming (4 pins).
3. Limit Switch Screw Connector (3 pins). Total of 3, for axis: X, Y, Z.
4. Main Power Connector.  Tip Positive, DC 12V 1A recommended.
5. USB mini Connector, for Main Communication (using onboard CH340 USB to Serial Chip).
6. Header for Digital AUX Outputs (5 pins).
7. Header for I2C communication (5 pins).
8. Power Out Screw Connector (3 pins).
9. External Power Screw Connector for Stepper Drivers.
10. Stepper Driver Power selection jumper: Main or External Power.
11. Connector for Pololu style Stepper Motor Driver. Total of 3.
12. Micro-Step Selection (3 jumpers) for Stepper Driver. Total of 3.
13. Stepper Motor Screw Connector (4 pins). Total of 6.
14. Communication Selection Jumper.
15. Spindle Control Screw Connector (6 pins).
16. Probe Input Screw Connector (2 pins).
17. System Control  Screw Connector (6 pins).
18. System Control Signal Pull Up/Down Selection Jumper (J13). Limit Switches Pull Up/Down Selection Jumper (J14).
19. Firmware Programming Jumper (J12).

Mounting Holes Locations.  The holes' size is 0.125" (3.16mm), the pad size is 0.225" (5.72mm). Suitable standoffs and screws are 4-40 or smaller for imperial, M3 or smaller for metrics.

If the final integration requires a chassis ground, the upper left hole/pad is connected to ground.

(10) Stepper Driver Power selection jumper: Main or External Power

Default: Use the main power input (4) for the stepper drivers. This is usually for testing or running very low power stepper driver/motor only. In most applications, a separate power source should be used for the stepper drivers/motors. If only external drivers are used (via ED1), then the VMo is not necessary, the jumper can be removed.

Select the Vext (9) power source for the stepper drivers/motors.

(12) Micro-Step Selection

Default: All three positions jumpered. This is usually the highest micro-step count setting for the driver. Refer the the actual driver's documentation for micro-step resolution selection.

(14) Communication Selection Jumper

Default: Communication is via onboard USB to serial (CH340 chip). Remove all jumpers to connect a TTL-Serial UART directly. Popular choices include CH340, FTDI, CP2102, or another micro-controller for custom implementations. Connect the UART TX pin to the indicated rx pin, similarly RX to tx, and Ground to gnd. Comm Baud Rate is 921,600.

(18) System Control Signal Pull Up/Down Selection Jumper (J13). Limit Switches Pull Up/Down Selection Jumper (J14).

Default: both J13 (Control) and J14 (Limits) are in Pull-Up Positions.

J14 (Limits) Pull-Up.
J13 (Control) Pull-Down.

(19) Firmware Programming Jumper (J12).

Default: jumpered for normal operation. Remove jumper for firmware programming.

(4) Main Power Connector.

Main power for the board is via a standard 5.5mm x 2.1mm tip-positive connector. The board will accept power supplies from 5V to 12V.

Depending on the final configuration, the recommended power supply is as followed:

For board logic only : 5V 1A
With low current stepper drivers : 12V 2.0+ A, depending on how many axis. With higher current drivers, separate power for the drivers is recommended (see below).

(9) External Power Connector.

For higher current applications, use this screw connector to provide power for the stepper drivers. Note the positive (+) pin location, there is no reverse voltage protection for most drivers. Selection of the power supply will depend on the driver; for example, the popular A4988 can handle up to 35V, and the DRV8825 can handle up to 45V. The current requirement for the power supply will depend on the final application, refer to the driver and motor specifications for power supply selection.

The F13 has an onboard USB to Serial UART (CH340). Connect the USB mini cable to the USB mini port (5).

The user can also use an external UART or Comm from another MCU. Connect the TX, RX, and GROUND pins from the external UART to the rx,tx,gnd pins (respectively) at the labeled pins (see bottom silkscreen or above jumper settings).  For example: The Raspberry Pi (zero, zero W, 2, 3, similar clones), GPIO pins 6, 8, 10 are Ground, TX, RX respectively; this is a straight connection to the F13 ground, rx, tx pins.

From Left to Right: Connectors for limit switches, for axis Z, Y, X.

There is one limit signal for each axis. This signal is split to two pins for connecting two limit switches for each axis. The pins are Ground, then 2 Limit signals. This configuration is typical for connecting passive 2 pin mechanical switches, where the switch simply connect the signal pin to ground.

Spindle and Control Connections

Spindle Control Inputs (15):

1. Coolant Flood Output to coolant control.
2. Coolant Mist Output to coolant control.
3. Spindle Enable Output to spindle motor driver.
4. Spindle Direction Output to spindle motor driver.
5. Spindle PWM Output (0 to 5V) to spindle motor driver. Also used for PWM control of Laser cutter/engraver.

Probe Input (16):

1. Input from touch probe.

Spindle/Laser Outputs (17):

1. Control Reset
2. Safety Door
3. Cycle Start
4. Feed Hold
5. Emergency Stop (connects to STM32F103 reset line)

Driver connections, from left to right, axis: Z, Y, X.

These are Pololu-style connectors. Notice the orientation warning as the wrong orientation will damage your driver. Look for the EN and DIR pin labels on the driver and match them to the board labels. In this example, and ED1 External Driver Jumper board is mounted for Z. X and Y have the popular DRV8825 mounted.

Motor connections. For each axis, connect the 4 screw connector pins (L to R): 2B 2A 1A 1B to the corresponding wires of the bipolar stepper motor. If the External Driver Jumper board is used,  the 4 screw connector pins are now ENABLE, STEP, DIRECTION, GROUND.