The microcontroller used is a Microchip PIC18F2550. The PIC18F2550 runs at 48MHz using the internal PLL. R1 is a pull-up resistor necessary for operation.
The microcontroller USART pins need to be connected to a RS-232 Level Converter to connect to a PC for firmware updates using the Tiny PIC Bootloader. Otherwise, after initial programming they can be left disconnected.
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