v1.1

Numerous improvements to the control board PCB:

• Change MCU to STM32F103CBT6.
• Add USB D+ pull-up resistor.
• Remove copper fill around mounting holes.
• Use a different buzzer.
• Add a snubber diode to the buzzer circuit.
• Use Schottky flyback diode for the heatbed.
• Miscellaneous changes.

Other PCBs were not changed.

v1.0

The first revision of the hardware.