README.md
tinyDiskII

Homemade floppy disk emulator for Apple II series computers


  
:warning: Work in progress: read carefully the README before trying to reproduce this project!




tinyDiskII is able to simulate an <![CDATA[]]>Apple Disk II<![CDATA[]]> 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.

BOM




  
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




Do Not Place, reserved for future implementations:




  
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


  
:warning: Schematics and PCB layout can be found in /schematics folder. 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

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


Changelog


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.



Contributors and references

The whole projects borns as a custom implementation of Koichi Nishida's SdiskII <![CDATA[]]>[1]<![CDATA[]]> <![CDATA[]]>[2]<![CDATA[]]>, which I used as a starting point for firmware developement.