Homemade floppy disk emulator for Apple II series computers
⚠️ Work in progress: read carefully the README before trying to reproduce this project!
tinyDiskII is able to simulate an Apple Disk II both in reading and writing. Disk images are stored into a FAT16 formatted SD Card. Each disk image must be a DOS 3.3 floppy image, saved as .NIC. A cross platform .NIC <-> .DSK conversion tool will be available soon on this repository. Floppy formatting is currently not supported, but it is currently under developement.
| Reference(s) | Description | Notes |
|---|---|---|
| C1, C2, C3, C4, C5, C6, C8, C9, C10, C11, C12 | 0805 100n Capacitor | |
| D1, D2 | 0805 Red LED | |
| J1 | 2x3 male jumper | ICSP connector |
| J2 | SMD SD Card slot | |
| J3 | THT USB B Mini connector | Mount for USB debug |
| J4 | 2x10 male connector | DiskII connector |
| R5, R6 | 330 | |
| R2, R3, R4, R7, R8, R9, R10, R11, R12, R15 | 10k | |
| R13, R14 | 0 | Replaced with a bridge |
| SW1 | RotaryEncoder with switch | |
| U2 | SN74LVC244 | 5V tolerant buffer |
| U3 | CH340C | Mount for USB debug |
| U4 | ATxmega16A4U-A | MCU |
| U5 | 74AHCT125 | Level shifter |
| U7 | 0.96" OLED I2C | 7-pin model |
| U10 | AP1117-33 | 3v3 linear regulator |
| Reference(s) | Feature |
|---|---|
| U1 | Flash/EEPROM interface |
| C12 | " |
| R1 | " |
| C13, C14 | USB ESD |
| R13, R14 | " |
| D3, D4 | " |
| C7 | USB self reset |
| J5 | Debugging connector |
⚠️ Schematics and PCB layout can be found in/schematicsfolder. Please note that I had physically implemented only rev1.0, which requires some hardware patches. The issues were fixed in rev1.1, but I never put it into production. Build it at your own risk.
Firmware source code is in /firmware folder.
Code can be compiled on a linux/wsl machine through make command.
Make sure you have make and avr-gcc toolchanin installed.
Output binary will be generated as /firmware/output/tinyDiskII.hex.
In /firmware/tests there are some unit tests that can run on host system.
They can be compiled and executed with:
cd firmware/tests
cmake -B build .
cd build
cmake --build .
./tinyDiskII-tests
-
rev1.0: first version
-
rev1.1: fixes the issues present in rev1.0:
- LV_DISK_READ connected to U4 pin 21;
- SD_WP connected to U4 pin 22;
- SD_DETECT connected to U4 pin 23;
- Added 10K pull-up resistor to DISK_WRITE_EN;
- Pin 4 and 16 of U3 are shorted together.
The whole projects borns as a custom implementation of Koichi Nishida's SdiskII [1] [2], which I used as a starting point for firmware developement.