Author Topic: DDI-1 DIY  (Read 1097 times)

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Offline khaz

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Re: DDI-1 DIY
« Reply #20 on: 15:11, 14 November 17 »
The disks are not double sided on the original DDI-1? Do I need to add a jumper to switch sides?
I see that an output signal /SIDE1 exists and is driven directly by the uPD765...[/font]

Parados, and other custom DOS can access both sides directly, but only for floppies formatted for it (like ROMDOS format or games with a custom DOS like Orion Prime). If you try to put two standard DATA dsk images on your 3.5, you will only be able to access one.

Offline khaz

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Re: DDI-1 DIY
« Reply #21 on: 15:13, 14 November 17 »
Moving the PCB to the other end of the cable (at the drive end) won't work. The expansion port signals aren't buffered and are too weak to drive a signal down a meter of cable. They are also much more likely to damage the CPC through static discharge - Long plastic cable connected directly to CPU pins = bad idea. The DDI-1 has buffered outputs to allow the cable to the drive to be that long.

A meter haha, I wasn't planning to put the drive on the other side of the room. Even something like 30cm is too long for that?

I had no idea about that sort of challenge.

Offline SilverGreen93

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Re: DDI-1 DIY
« Reply #22 on: 15:18, 14 November 17 »
Parados, and other custom DOS can access both sides directly, but only for floppies formatted for it (like ROMDOS format or games with a custom DOS like Orion Prime). If you try to put two standard DATA dsk images on your 3.5, you will only be able to access one.


Ok, I will add a jumper to ground if you say that it is required for other types of floppies. Does the standard BASIC floppy type require this to use both sides?


@Bryce, is this modification ok for all floppy types?

A 3 pin jumper like this:

/SIDE1 >--------*
                        *--------------> to pin 32
GND >-----------*
« Last Edit: 15:20, 14 November 17 by SilverGreen93 »

Offline Bryce

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Re: DDI-1 DIY
« Reply #23 on: 15:21, 14 November 17 »
Even 30cm could be an issue without buffers / line-drivers.

The side select is fine for 3.5in drives, but it would need to be switched if a 3in drive is connected.

Edit: It's not a simple "jumper to ground". Here's how it has to be connected: http://www.cpcwiki.eu/index.php/Side_Select_Switch

Bryce.
« Last Edit: 15:24, 14 November 17 by Bryce »

Offline SilverGreen93

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Re: DDI-1 DIY
« Reply #24 on: 22:51, 14 November 17 »
Edit: It's not a simple "jumper to ground". Here's how it has to be connected: http://www.cpcwiki.eu/index.php/Side_Select_Switch


Well, isn't that what I suggested above? a switch between GND and /SIDE1 connected to pin 32? I don't quite get the picture from the link, what has it to do with pin 1 and pin 34?

Offline Bryce

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Re: DDI-1 DIY
« Reply #25 on: 10:01, 15 November 17 »
Yes, I didn't read you ASCII art properly. I though you were suggesting grounding pin 32 without cutting it.

Bryce.

Offline SilverGreen93

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Re: DDI-1 DIY
« Reply #26 on: 10:17, 15 November 17 »
Yes, I didn't read you ASCII art properly. I though you were suggesting grounding pin 32 without cutting it.


Well then, I'll try to respin the board in a couple of days, including the side switch/jumper and the lower profile, and come back.

Offline khaz

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Re: DDI-1 DIY
« Reply #27 on: 13:58, 15 November 17 »
Edit: It's not a simple "jumper to ground". Here's how it has to be connected: http://www.cpcwiki.eu/index.php/Side_Select_Switch

What's wrong with simply grounding the connection? This is how most cables are made, and it works. See for example http://www.cpcwiki.eu/index.php/Guide_on_how_to_connect_a_3.5%22_drive_to_a_CPC6128/664

Offline Bryce

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Re: DDI-1 DIY
« Reply #28 on: 14:52, 15 November 17 »
Because you are essentially connecting the output of a 74LS38 in the floppy controller to ground. This output can supply a maximum current of 250µA. So after a while you will have destroyed at least this output channel of the 74LS38 if not the entire IC. Which is why I recommend people to avoid these types of cable (although they provide me with a steady supply of repair work :) ).

Bryce.
« Last Edit: 14:54, 15 November 17 by Bryce »

Offline SilverGreen93

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Re: DDI-1 DIY
« Reply #29 on: 23:04, 16 November 17 »
New design ready! (v2)
Added SIDE selection jumper as discussed above.
Reduced the overall dimensions to (LxH): 97x93mm
Positioned the ROM beneath the expansion connector.