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 rev1.0 hardware requires some physical changes, so if you are interested to fabricare the PCB, check out the following updated schematic first.
Manual fixes are highlighed with red lines:
- 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.
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
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.