Retro tool to read Apple II formatted DOS 3.3 disk content using Arduino Mega2560 and store it via USB on a host PC

treckr: Retro tool to read Apple II DOS 3.3 formatted 5.25 inch disks using disk drive, Arduino board and host PC. Designed for (former) Apple II hobby enthusiasts who would like to recover private disk content.

Version: 0.5 - May 30, 2019 - Eckhard Delfs

Which equipment is needed?

To be able to read DOS 3.3 disks and store them on a PC host via USB, the following equipment is needed:

How are the HW components connected to each other?

For connecting the 20-pin HW drive connector to the Arduino board, please have a look at the suggested schematic using a custom power supply. The overall HW tool kit used during development is shown here.

Required wiring between Arduino and disk drive:

The host PC is interfacing with Arduino via USB. PC needs to support Python 3.5. Only W10 has been tested, but other OS should work as well.

Arduino PIN configuration

The Arduino board PIN configuration is as follows:

This PIN configuration can be changed in the Arduino SW if needed.

Disk drive power supply

The following choices are suggested:

For prototyping, the second option was used. A standard power supply (18W) providing 15V DC output has been chosen. The +12V and +5V rails can be generated easily using 7812 and 7805 voltage regulators and additional capacitors for input/output. Note that decent heat sinks are needed, in particular for the 5V rail feeding the disk drive logic even when the motor is powered off. The negative voltage (-12V) was realized using a charge pump DC->DC converter, such as IC7662A. Two addditional 10uF capacitors are required for the charge pump. The 12V rail needs to be connected to the Arduino board as well.

NOTE: Before enabling the power supply to the drive and connecting the drive control signals to the Arduino board, check the wiring. Info can be found in online Apple-2 material, also see below hints for literature. Incorrect wiring may damage your Hardware! Please note treckr is not designed to modify the disk content. However, it is strongly recommended to write protect disks before inserting them in the drive.

Software Description

The general concept of treckr is shortly described as follows:

Note: treckr only supports reading DOS 3.3 disks. Writing is not supported.

The following books were considered very helpful:

The author reserves the right not to be responsible for the topicality, correctness, completeness or quality of the information provided. Liability claims regarding damage caused by the use of any information provided, including any kind of information which is incomplete or incorrect, will therefore be rejected. The tool is intended to be used for personal purposes only.