GRBL GRBL32 3-Axis CNC Controller F13 – 250KHz


3-Axis 32-bit ARM based CNC Controller. STM32F103.

SKU: G32F13 Category:

The F13 is the perfect upgrade for existing GRBL systems. Featuring a much faster 250KHz pulse rate, smoother control, and higher resolution PWM output for better Spindle or Laser control. With the faster pulse rate, more advanced stepper drivers can be used (featuring up to 256 micro-steps/full-step) without sacrificing feed rate.

The F13 is running GRBL32 (an upgrade from the popular GRBL firmware running on an Arduino 328p processor). The GRBL32 firmware is a fork from GRBL version 1.1f, running on the 32-bit STM32F103 (aka “bluepill”). With a 32-bit Arm Cortex-M3 core overclocked to 96MHz, the STM32F103 is much faster than the 8-bit Arduino 328p running at 16MHz.  At 20kB RAM and 64kB flash, STM32F103 has 10 times the RAM and twice the flash, allowing many enhancements to the core GRBL.

F13 enhanced GRBL32 features:

  1. Up to 250KHz max pulse rate for each axis while under 3-axis coordinated motion (up from 30KHz for Arduino based GRBL).
  2. Smoother Acceleration/Deceleration (0.2 ms accel/decel step).
  3. 96MHz timer for flexible PWM output control. Default is 10KHz PWM at better than 13-bit resolution : 9600 steps in the 0 to 5V range.
  4. USB or external UART connectivity options (921600 baud rate, 115200 firmware available).
  5. Four (4) AUX TTL output (M-Code control: M62/M63)
  6. Custom Acceleration Scaling (custom M-Code control: M100), allowing in-code changes of the acceleration parameter for each axis individually.
  7. I2C output for expansion (via M-Code controls).

See here for standard GRBL features.

User’s Manual.


Demo Video

GRBL GRBL32 3-Axis CNC Controller F13 – 250KHz


3.92 x 1.95 in. (100 x 50mm)


STM32F103C8T6 overclocked to 96MHz

Maximum Pulse Rate


Peripheral Connections

3.5mm screw terminals for CNC Control, Spindle Control, Limit Switches. 0.1" (2.54) headers for I2C and Digital Outputs.

Stepper Driver Connection

Pololu-style connector socket for driver, 3.5mm screw terminals for motor connection.

External Driver Connection

via External Driver Jumper ED1 board, convert motor connection to STEP, DIR, ENable, GND.


6V to 12V DC. 5.5 * 2.1 mm tip positive connector.


USB mini (on-board CH340). External UART via header pins. 921.6K baud-rate standard. 115.2K optional.

Programming Interface

Serial Wire Debug (SWD) pins on STM32F103C8T6 module using the USB ST-Link V2 programmer.

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