8235 External FDD port: how to use it

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By ateodoro

Supporter (14)

ateodoro's picture

25-02-2021, 18:21

Hi all,
I'm trying to use the external FDD port in my Philips VG8235.
I've not an user manual and in the Internet I've only found the service manual.
So I've looked here in every possible thread but I've seen that the question is still opened and it's not well known how to use an external drive (if it's possible!!!) with this wonderfull machine.
Does anyone have the user manual for VG8235 or have successed to connect the computer to some external floppy or Gotek drive? How?

I've done the same tests that in some threads have successed for someone, even if they are not so detailed, so I think I have done some not correct steps in my test ones.

I've used for external connection a Shugart ribbon cable but the ony result is that the command "files" reads on prompt the files into my floppy or disk img selected by the Gotek.
If I try to execute or load some files there is the message the disk is off line.
I've tried with Philips VY-0010 floppy drive and with a Gotek configured in Shugart type, with host=msx.
I've also disconnected enterely the internal drive, as someone advices in those threads.
So I think that the connection Shugart type is not correct for the external fdd connection in the VG8235.

The only reference I've found is in this page MSX CONNECTORS AND CABLES and External drive connector VG8235 dosn't seem to be Shugart for the pins 1,2 and 4.

Please, can anyone help me? Smile

Many thanks in advance.
Alberto

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By Meits

Scribe (6328)

Meits's picture

25-02-2021, 20:29

Luck has it I received a """new""" diskdrive by mail yesterday and what better way to test it than with a 8235.
The drive was hardwired as B: drive.
The computer is modded with a double sided disk rom and rewired to actually be able to work with double sided disk drives. The rewiring is at least necessary for internal double sided drives. I'm not sure if the external drive requires it as well.
I used a default 34 pin data cable (no twists or whatsoever) from an NMS8250 and some power from an ATX PSU.

The drive turned out to be ok, so it's an A: drive now and got installed in another computer.

By ateodoro

Supporter (14)

ateodoro's picture

25-02-2021, 21:07

Thank you Meits.
You are very kind for the answer and for sharing your test.
I'm happy you have succeded to connect the external drive Big smile

So in your case there is the mod for the fdd rom suitable for double sided floppy (a 8245 fdd rom).

But I'm curious if the original 8235 could ever have been connected to an external floppy drive and what kind of drive it was
Possibile no information exist in some user manual or rerence book?

Ciao
Alberto

By Meits

Scribe (6328)

Meits's picture

25-02-2021, 23:47

ateodoro wrote:

But I'm curious if the original 8235 could ever have been connected to an external floppy drive and what kind of drive it was
Possibile no information exist in some user manual or rerence book?

I've never tried and I don't have all flavours (roms/drives), though my guess is that a virgin 8235 can only handle single sided diskdrives. I've heard otherwise, but I've never seen it happen.
There are tutorials on how to mod your machine to work with double sided drives.

Have you tested what your internal drive does on the external connector? You do need a cable adapter for that, but they're available.

By sdsnatcher73

Paragon (1646)

sdsnatcher73's picture

26-02-2021, 06:40

Philips sold the VY0010 and VY0011 in those days. The VY0011 is without the interface cartridge and I am sure it works on a VG8235 (I think the OEM drive is even the same as in the VG8235). It reportedly even works on a Sony interface cartridge.

By ateodoro

Supporter (14)

ateodoro's picture

27-02-2021, 13:21

Hi all Smile
Thanks for all helps and advices.

In the end I succeeded to use the external fdd connection of my VG-8235.
Now I put here some details hoping they could be useful to some other ones like me.

I've found the solution for my case here: CREDIT

I've the model VG-8235/20 so I've also connected the CN3 PIN6 to the CN15 PIN10: probably this connection could need to say to the ext fdd to become S0 and the internal fdd to become S1 ... but I'm not sure for this.


Then I've done by myself a Shugart ribbon cable, starting from a PC ribbon cable, and I've paid attention to invert btween themeselves the PIN 10 with the PIN 12.

I've done the first test with a Gotek configured for MSX:
hot=msx and interface = jc into the ff.CFG file and jumpers put to close MO and S0

I've noticed that both the internal fdd and the external Gotek were running when I were doing the commands FILES or RUN "A:" or RUN "B:".
Then I've used the POKE comand:
first test using POKE &hf247,0 to set the default fdd to Α:
second ones using POKE &hf247,1 to set the default fdd to B:
but I had always the internal fdd running.

After these first test the loading from Gotek didn't work anymore: I don't know if could be caused by my ribbon Shugart cable or because the cooesistent internal and external fdds. The connection adviced between CN3 PIN6 and CN15 PIN10 probably does not exclude the internal FDD.

So I've removed the power supply of the internal fdd to exclude it.

After this action the Gotek connected to the external port worked properly again:
it lets the boot from some disk images, such as MSX Hme Office, EASE and other games selected from Gotek

Here I've put some videos about my tests:
Boot test1 from Gotek https://www.youtube.com/watch?v=tPbpLfVHQMk
Boot test2 from Gotek https://youtu.be/dDj2Z7dqfH8
Boot test3 from Gotek https://youtu.be/2LYVB-5eIZk
Boot test4 from Gotek https://youtu.be/cxesFXrrcmM

The Next step will be:
1) to set a switch for choosing the exclusion of the internal fdd when I use the external fdd port
2) test a real fdd device such as the VY-0010

By ateodoro

Supporter (14)

ateodoro's picture

27-02-2021, 14:43

For inserting the images Wink

ateodoro wrote:

Hi all Smile
Thanks for all helps and advices.

In the end I succeeded to use the external fdd connection of my VG-8235.
Now I put here some details hoping they could be useful to some other ones like me.

I've found the solution for my case here: CREDIT

I've the model VG-8235/20 so I've also connected the CN3 PIN6 to the CN15 PIN10: probably this connection could need to say to the ext fdd to become S0 and the internal fdd to become S1 ... but I'm not sure for this.


Then I've done by myself a Shugart ribbon cable, starting from a PC ribbon cable, and I've paid attention to invert btween themeselves the PIN 10 with the PIN 12.

I've done the first test with a Gotek configured for MSX:
hot=msx and interface = jc into the ff.CFG file and jumpers put to close MO and S0

I've noticed that both the internal fdd and the external Gotek were running when I were doing the commands FILES or RUN "A:" or RUN "B:".
Then I've used the POKE comand:
first test using POKE &hf247,0 to set the default fdd to Α:
second ones using POKE &hf247,1 to set the default fdd to B:
but I had always the internal fdd running.

After these first test the loading from Gotek didn't work anymore: I don't know if could be caused by my ribbon Shugart cable or because the cooesistent internal and external fdds. The connection adviced between CN3 PIN6 and CN15 PIN10 probably does not exclude the internal FDD.

So I've removed the power supply of the internal fdd to exclude it.

After this action the Gotek connected to the external port worked properly again:
it lets the boot from some disk images, such as MSX Hme Office, EASE and other games selected from Gotek

Here I've put some videos about my tests:
Boot test1 from Gotek https://www.youtube.com/watch?v=tPbpLfVHQMk
Boot test2 from Gotek https://youtu.be/dDj2Z7dqfH8
Boot test3 from Gotek https://youtu.be/2LYVB-5eIZk
Boot test4 from Gotek https://youtu.be/cxesFXrrcmM

The Next step will be:
1) to set a switch for choosing the exclusion of the internal fdd when I use the external fdd port
2) test a real fdd device such as the VY-0010

By Briqunullus

Champion (318)

Briqunullus's picture

27-02-2021, 20:05

Pin 10 and 12 of the external connector are the drive select signals. Pin 10 is drive select 0 (or A: for us humans) and pin 12 is drive select 1 (BSmile. The Gotek drive will listen to one of these signals, depending on its jumper settings. If you have put the jumper on S0 it will react to drive select 0, if you have put the jumper on S1 it will react to drive select 1.

Apparently the drive select 0 is not connected to the external connector in a 8235/20, that's why you had to make a connection between CN3/PIN6 and CN15/PIN10.

Switching the wires in the ribbon cable is only necessary for drives that don't have jumpers like these. If your drive is hardwired to be A: it will be connected only to drive select 0. By switching the wires you reroute the drive select 1 to that connector pin and that drive can be used as B:.

I use a straight 1:1 ribbon cable to connect the Gotek to the external port of my 8235/00 with S0 jumper set. It works fine, the internal drive has been disconnected as it is broken anyway.

By the way, have you replaced the diskrom of your 8235?

By Meits

Scribe (6328)

Meits's picture

27-02-2021, 20:27

Briqunullus wrote:

By the way, have you replaced the diskrom of your 8235?

Curious to know because the gotek reads two sides.

By ateodoro

Supporter (14)

ateodoro's picture

27-02-2021, 23:23

Hi Briqunullus,
I've tried using a straight 1:1 ribbon cable, before all these tests, but nothing: both Gotek (S0 or S1 or nothing) and the external floppy driver, a VY-0010, only could read the disk contents and nothing all. No run, no load , no boot... nothing ☹️ ... only disk off line message from the prompt.
When I've inverted pin10 and pin12 all worked fine instead.

I didn't replace the diskrom: I have the original one. I want to use the original internal floppy and together an external floppy, because an external port was provided for this model Wink

By ateodoro

Supporter (14)

ateodoro's picture

27-02-2021, 22:22

Meits wrote:
Briqunullus wrote:

By the way, have you replaced the diskrom of your 8235?

Curious to know because the gotek reads two sides.

I think It does not depend because of the Gotek ... probably the external port was enabling the computer to connect to a 720k floppy driver.
The strange thing is that no information about this external port are at dosposal anywhere.

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