ICL OPD

[Pr0f]

time to unearth my stash of 3.5" DD floppy drives I am sure I've got some 5v only ones too - unless they are HD, not that I would try and power the drive from the dongle, but I am thinking of putting the floppy in the box I use for the power supply and QLPICO VGA interface.

[stephen_usher]

I've written a program to change the C1 floppy boot parameter block to an MSDOS one. Looks like the C1's FAT12 isn't quite as it should be:

Code: Select all

[root@nowhere opd]# mount -t msdos /dev/loop0 /mnt
[root@nowhere opd]# ls /mnt
ls: cannot access '/mnt/myfile.doc': No such file or directory
dr240110.181*  dr240110.181*  dr240110.182*  myfile.doc
[root@nowhere opd]# ls -al /mnt
ls: cannot access '/mnt/myfile.doc': No such file or directory
total 13
drwxr-xr-x  2 root root 3584 Jan  1  1970 ./
drwxr-xr-x 26 root root 4096 Sep 13  2022 ../
-rwxr-xr-x  1 root root 1024 Jan 10 18:11 dr240110.181*
-rwxr-xr-x  1 root root 1024 Jan 10 18:11 dr240110.181*
-rwxr-xr-x  1 root root 3072 Jan 10 18:20 dr240110.182*
-?????????  ? ?    ?       ?            ? myfile.doc

Hmm....

[Derek_Stewart]

Hi,

Do you have the main board schematics, maybe a a new PCB could be made.

[stephen_usher]

Here's the program. From what I can see it should have the correct parameters.

[Pr0f]

Hi,

Do you have the main board schematics, maybe a a new PCB could be made.

Derek - Stephen posted the KiCad files in the thread earlier But note the issue with the clock generator and fix for this.

[Chr$]

Here's the ROM image.

Thanks for sharing that.

I can't find at a glace what the electrolytic capacitor values should be or the details of the resistor network. The chips and resistors are clearly visible. I've ordered some PCBs and am looking forward to setting it up with the OPD. Pr0f, I'm sure any common 1.44mb PC drive will do the trick, it won't need to be an older, scarcer 720k drive.

[Pr0f]

It's just I seem to have more of them than the 1.44MB variety - lol

[stephen_usher]

Here's the ROM image.

Thanks for sharing that.

I can't find at a glace what the electrolytic capacitor values should be or the details of the resistor network. The chips and resistors are clearly visible. I've ordered some PCBs and am looking forward to setting it up with the OPD. Pr0f, I'm sure any common 1.44mb PC drive will do the trick, it won't need to be an older, scarcer 720k drive.

All the decoupling caps are 1pF, the resistor pack should be 1K, but I just used a 2.2K as that's what I had. It's just a pull-up for the floppy lines.

The values are all on the schematic in the KiCAD files.

As for the drive type, I don't know if it requires /READY on pin 34, that would be a software thing. Until I disassemble the ROM I can't tell.

[Pr0f]

On some of the retro brew projects I've seen those as low as 300 Ohms - but that's with a different floppy controller that drives quite a high current - the LS TTL chips are probably not going to want to see that low a load.

I suspect the decoupling capacitors should be 100nF as that's almost a standard size for that job, the electrolytic could be anything between 10 and 100u - depending on what fits - rated at 10V or 16V

[Derek_Stewart]

Hi,

Do you have the main board schematics, maybe a a new PCB could be made.

Derek - Stephen posted the KiCad files in the thread earlier But note the issue with the clock generator and fix for this.

Can't find the main board cad files, only the disk interface.