Simple PC parallel port OpenServo bootstrap flasher

Presented are two designs for a In Circuit Flasher for the OpenServo boards. These can be used to get the initial software into the board (bootstrapping), as well as reflashing new firmware.

• The buffered design presented below sources it's power from the PC parallel port. It will supply only enough power to flash the board. This may not work with some PC parallel port, and most laptops.

• The unbuffered design requires an external +5V source in order to power the MCU while flashing. This design has no protection for either the PC or the OpenServo, and a bad board could possibly destroy your parallel port.

• Pin 1 is marked on all of the boards, and the corresponding connections can be found on this page OpenServo Pin configuration

• The 8 pin connector I used is a female header type. This allows the OpenServo to slot straight in, but only if you have soldered a male header to the servo. You can substitute the female header onboard with a 8 pin edge connector slot.

Buffered design

A "safe" buffered programmer for the OpenServo.

The schematic.

Both the bottom layer and the top layer. Red on the top layer is a wire link.

The bottom of the PCB. Note this is not to scale.

Unbuffered design

This does away with the buffer, and although will work, it does not protect the OpenServo from potential voltage spikes. There is the possibility that you will fry your PC parallel port if you connect faulty hardware.

The buffered schematic.

Both the bottom layer and the top layer. Red on the top layer is a wire link.

Bottom of PCB. Note this is not to scale.

Download the Eagle PCB files below:

• Simple programmer SimpleProgrammerEagleSch.sch Schematic

• Simple programmer SimpleProgrammerEagleBrd.brd PCB

• Buffered programmer BufferedProgrammerEagleSch.sch Schematic

• Buffered programmer BufferedProgrammerEagleBrd.brd PCB