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65C02 Single Board Computer - Dual Channel Servo Controller

Last Update: September 29, 2014

  1. Introduction
  2. Features At a Glance
  3. Block Diagram
  4. Schematic Diagram
  5. Memory Map
  6. Part List


Note: This project is under development; this document is incomplete at this time and may be inconsistent.

Note: This project is part of an ecosystem of boards designed around a 65C02-based single board computer.

The basic platform of the BoE-bot kit (and a number of other Parallax kits) is an aluminum chassis with a caster wheel and two continuous rotation servos with attached wheels. These servos have an interface that is identical to the classic hobby servo:

TODO: Signal waveform diagram

This board follows the general ideal set forth in the 6502sbc project: parts that are cheap, generic, and readily available; through hole construction for easy hand assembly; well documented design to encourage investigation and experimentation.

Features At a Glance

Block Diagram

Schematic Diagram

Schematic in EPS and PNG.

Bill of Materials


Memory Map

A2 A1 A0 Description
0 0 0 8-bit control register (set bits to 1 to active servo channels)
0 0 1 Servo Channel A
0 1 0 Servo Channel B
0 1 1 Reserved For Future Use
1 0 0 Control register (again)
1 0 1 Servo Channel A (again)
1 1 0 Servo Channel B (again)
1 1 1 Reserved (again)

Note that there can be a max of seven servo channels, but this board only implements two.

Setting/clearing bits in the control register enables/disables each servo channel:

Bit Description
0 Servo Channel A
1 Servo Channel B
2 Reserved
3 Reserved
4 Reserved
5 Reserved
6 Reserved
7 User/Status LED (on/off)

A disabled servo channel should be considered 'free-wheeling' i.e. motor is powered but there is no motor drive signal.