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Model I solid state floppy

D

Druid6900

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May 7, 2006
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Hamilton, Ontario, Canada
I'm about to tackle a pile of 16K keyboard units and bare boards. I'm looking for something that may not exist.
A floppy drive emulator that doesn't require an expansion interface to work.
Does such a device exist and, if not, could such a device be built?
Unfortunately, I'm not a Raspberry PI designer nor a programmer, I just fix the stuff.
The idea behind this is to load diagnostic and do burn-in testing of the units.

Any thoughts?

TIA
Druid6900
 
Look up "FReHD" it is a hard drive emulator that uses a SD card for storage. There is a potential issues that I see for you.
1 is that a FReHD needs either a floppy to boot or the ROMs updated to have DOS installed.
How this helps
Rick
 
Something similar to how the Extatron Stringy Floppy interface worked would do you. It didn't need the EI, it could plug right into the card connector on the keyboard unit. Sadly, I can't tell you how it worked.

g.
 
Druid6900 said:
I'm about to tackle a pile of 16K keyboard units and bare boards. I'm looking for something that may not exist.
A floppy drive emulator that doesn't require an expansion interface to work.
Does such a device exist and, if not, could such a device be built?
Click to expand...

I'm vaguely certain that someone has at least partially implemented this; I *think*, but don't have it in front of me, that the "Quinnterface" for interfacing a FreHD to a Model I without an expansion interface uses a PIC(?) MCU to emulate enough of the 1771 disk controller that it can feed the TRS-80 a fake boot sector with code to get things running off the FreHD.

One of the things on my long-term project list is to investigate if it might be reasonably possible to do a full emulation of a 1771/1791 with an MCU so for floppy emulation it'd be possible to skip the middleman of needing the original controller and a separate floppy emulator to use disk images with a machine where the original controller hardware is difficult to lay hands on. It'd be a useful thing to have for a lot of things; expansion-interface-less TRS-80 Model Is, cassette-only Model IIIs (although technically I think both of these use cases have options for using the FreHD), as an S-100 card, etc. I don't imagine it'd be a lot harder than a floppy emulator, of which several open source solutions exist, it might actually be easier because you can skip some timing-critical serialization/deserialization/etc. (Although you do substitute having to reliably interface with the parallel CPU bus on the other side.)
 
I am currently looking into this for the Model 4. The intent is to replace the Floppy Disk Controller (FDC) board and floppy drives with a single board with an SD-Card socket. So far I connected to the connector between the FDC and main board to see what the communication looks like. I designed a board and am waiting for it to come back from manufacture.

At that point I will remove the floppies and the FDC from the system and connect my board to it. Then development will start. It doesn't seem all that complicated from a development standpoint. Just respond to the requests from the main board.

As mentioned this is for the Model 4. I don't know if it would work with the Model I and III. But I will be interested in looking into that once this is working.
 
The Model 1 work fine with the Quinterface and FreHD (no 'real' diskdrive or E.I. needed). Bas in Corfu or Mav in Oz sell them. The UK's answer to the Exatron, the Aculab Floppy Tape is emulated in George & Peter's trs80gp. The real FT has a built in ROM and just plugs into the M1's expansion port.
 
Well, I looked at the FreHD but it's rather expensive for what I want to do. I may as well just hook up and E/I and floppy drive, which I am trying to avoid.
From what I remember of them, the Stringy Floppy was more of a high-speed cassette mechanism than a floppy type mechanism.
Eud, I agree that it would be handy. For my needs, it could have a socket for a real 1771/91 as long as when you plug it it, it says "SOB, look at that, a 32K E/I and a floppy drive" then use a memory card or flash drive to load the image you want.
Michael, sounds promising and I don't see that there would be a problem since several M1 operating systems could handle DSDD floppies.
Dustym, same problem, the Quinterace/FreHD is great if you're going to use it a lot, but, after fixing and testing this pile of boards, we wouldn't use it until another Model I came in for repair.
I guess what I need is something that looks like a floppy that I can load diagnostics on, that I can switch out the memory and FDC on (in case I want to hook up an E/I to the keyboard and hang it on the E/I system bus) to test everything.
 
I saw a device that is basically a "gotek" but for the cassette port. so its a cassette player replacement using an sd card for files storage.
As for price, I have not looked into it, but here are the details I found some times back and I was mildly curious about it. There was someone selling completed kits on eBay some times back, but I don't recall the price of the completed it,/

https://forum.system-cfg.com/viewtopic.php?f=18&t=7700
 
MichaelM01 said:
I am currently looking into this for the Model 4. The intent is to replace the Floppy Disk Controller (FDC) board and floppy drives with a single board with an SD-Card socket. So far I connected to the connector between the FDC and main board to see what the communication looks like. I designed a board and am waiting for it to come back from manufacture.

At that point I will remove the floppies and the FDC from the system and connect my board to it. Then development will start. It doesn't seem all that complicated from a development standpoint. Just respond to the requests from the main board.

As mentioned this is for the Model 4. I don't know if it would work with the Model I and III. But I will be interested in looking into that once this is working.
Click to expand...

I'm looking forward to hearing how your project progresses (maybe in its own forum post). Not sure about the Model I, but it should work with the Model III as the main board to FDC board interface appears identical. Also, Model III units could be upgraded to Model 4 without needing to replace the FDC board.
 
I got it to boot LDOS 5.3 on a NGA Model 4 and also boot LSDOS 6.3 on the same model 4. LDOS 5.3 is stable but still need a bit of work for a stable LDOS 6.3.
 
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