Drive swap on STe without cutting pins/tracks

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Drive swap on STe without cutting pins/tracks

Postby tzok » Wed Dec 27, 2017 8:42 pm

As I can't get the DIN14 plug to make my GOTEK an external drive, I have not tested presented solution, but I believe that there is a way to swap A: and B: without (well, almost) cutting and/or bending any pins. It has two variants (STe only).

* First variant is to install ID switch (1P2T) in the Atari, and in the external drive. ID0 for EPSON SMD380 is by shorting pins 14 & 15, while ID1 is by shorting pins 15 and 16. You have to enable DS0 signal for external floppy by cutting a bridge between pins 2 & 3 of W300 and connecting pin 2 of W300 with pin 1 of W301. The drawback is that you have to move 2 independent switches to swap drives A and B.

* Second variant requires only one switch in the Atari. It has to be a two circuit ON-ON switch (2P2T). One circuit switches the internal drive by shorting jumpers 14 or 16 with 15. Second circuit switches pin 2 of W301 between 1 (DS0) and 3 (DS1), effectively switching external drive between ID0 and ID1. In this case you have to cut bridge between pins 2 & 3 of W301.
Be careful and think what you're doing - it has to be a cross-switch:
- in one position internal drive is ID0 (SMD380 pins 14 & 15 shorted) and DS1 signal is routed to the external drive (W301 pins 2 & 3 shorted),
- in second switch position it should be opposite: internal FDD is ID1 (SMD380 pins 16 & 15 shorted), and DS0 (W301 pins 2 & 1 shorted) is routed to the external FDD.

Pin 1 of W30x is a square pad.

I have noticed that D0SEL signal from YM2149 also goes to the U307 (74LS244) of DMA port to create BD0SEL. If one would swap signals by YM pins 19 & 20, then effectively D1SEL would create the BD0SEL signal (which I can't find where it goes). I'm not sure which method is better (swapping signals directly by YM2149 pins or switching FDDs between ID0 and ID1).

Pinout for selecting SMD-380 as DS0/DS1 is as follows:
Image
Last edited by tzok on Sun Sep 16, 2018 9:03 pm, edited 1 time in total.

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Re: Drive swap on STe without cutting pins/tracks

Postby tzok » Tue Jan 02, 2018 4:15 pm

I have tested that solution (no. 2) and I may confirm that it works flawlessly. The BD0SEL is a signal driving the FDD LED, so after swapping drives, the yellow LED indicates activity of external floppy (which is now drive A:).

The switches (TOS select and FDD swap) are mounted as follows:
Image Image

...and my external Gotek/FF looks like this:
Image Image

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Re: Drive swap on STe without cutting pins/tracks

Postby Dal » Tue Jan 02, 2018 5:09 pm

Nice solution!
Mega"SST" 12, MegaSTE, STE: Desktopper case, IDE interface, UltraSatan (8GB + 512Mb) + HXC floppy emulator. Plus some STE's/STFM's

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Re: Drive swap on STe without cutting pins/tracks

Postby tzok » Sat Mar 03, 2018 10:01 pm

Same option is available in the STf - the jumper is marked W2, and the positions are: 2-3 = DS1->PIN5, 1-2 = DS0->PIN5.

P.S.
Currently my Gotek/HxC looks like this:
Image

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Sun Apr 28, 2019 3:57 am

Dont suppose you have a mega STE to know where this goes on that computer eh? found the yamaha chip.. but no pads.

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Re: Drive swap on STe without cutting pins/tracks

Postby DoG » Sun Apr 28, 2019 5:22 am

W401 and W402 is the corresponding jumper pads on the Mega STe. Look at schematics in the archives.

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Sun Apr 28, 2019 2:24 pm

OH I know.. found them on the schematic.. Hmmm I am at work right now, so not looking at the board.. but I think those are right under the Floppy activity light .. and those have jumpers on them.. so I can just pull the signals right off the pins.. so this might end up being super easy.

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Last edited by Bikerbob on Sun Apr 28, 2019 2:27 pm, edited 1 time in total.

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Sun Apr 28, 2019 2:24 pm

Ok, so for a mega STE.. I think this is dead easy. There are two sets of 3 pins W401 and W402 as per this part of the schematics.
Atari_Mega_STe.jpg


SO a DPDT switch - each group of pins on each side of the switch should do it. These are the pins.
w401w402.jpg
mega_ste_wd17726.jpg


So the first picture shows only W401 and W402 is under the SCSI interface board. The 2nd shows the interface removed and the two sets of jumpers.

Just above the battery is a large flat area - should be a great spot to mount a switch. I am also installing 4mbit Eprom in mine, so this is where I will mount the switches for those TOS as well (4x tos)

If anyone sees something I am missing.. please share.

James
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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Fri May 03, 2019 2:53 am

anyone take a look at this for me please?

With 401 and 402 in the 2-3 position everything works.. Internal as A external as be.. in 1-2 position for both I would have thought it would reverse.. but now I get it trying to access both drives.. what am I missing??

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Re: Drive swap on STe without cutting pins/tracks

Postby DoG » Fri May 03, 2019 8:30 am

Sorry for not mention this in my previous post. But as you see on the schematics in the Mega STe, the internal floppy disk controller is always connected to DO select and D1 select no matter what you do with the jumpers. The jumpers only affect the external port.

D0 and D1 goes to pin 19 and 20 on U305 (the sound chip = AY-3-8910/YM2149).

I think most people does the switch on the chip by lifting the two legs (desolder) and then connect wires to the pads and legs and a DPDT switch.

You could also swap D0sel/D1sel on the internal floppy cable AND use the W401/W402 for the external floppy to swap things around. I don't have a Mega STe open at the moment so I can't remember if the floppy cable is soldered to the board. But if I remembered correctly, it is not. So you could do this mod on a new cable if you want. But all this is stated in the first post.

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Fri May 03, 2019 1:34 pm

Not arguing with you DoG, but what is the point of the jumpers then? In effect only 401 is needed.. I have now done tests.. that W402 is pointless because like you say its fixed.. SO.. why did they bother with the jumpers?

So I think I can do the same switch.. I now just need to go from 14,15,16 on the internal floppy on the one.. and then W401 on the other. SO I will give that a try.

OR.. I just thought of something.. on the drive what if I just leave it open.. NO jumper there period.. then the jumper on 402 would intercept the signal from the Yamaha and the drive would not be changing it.

More I think about this .. the more I dont understand why this does not work. In effect is not these jumpers the twisted cable? on a computer with a twisted cable I am not doing anything physical to the drive.. the cable flops the signal.. why does it not work here?

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Re: Drive swap on STe without cutting pins/tracks

Postby tzok » Fri May 03, 2019 2:54 pm

Jumpers only route DS0 and DS1 signals to the external FDD port. By default, in models which have an internal FDD DS0 is not routed to the ext. FDD port at all. That's why I only use one of these jumpers in my STe and I also switch the jumpers on the internal FDD. So in first switch position I route DS1 to the ext. FDD port and choose internal FDD to be D0, and in second switch position I route DS0 to the ext. FDD port, and switch internal FDD to be D1.
Second jumper is only useful when you want to disable the internal FDD and have two external FDDs.

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Fri May 03, 2019 5:58 pm

yeah.. thanks Tzok, just spent some time reading the schematic. On the Mega STE.. the way I read the schematic there is no way to disable DS0. and no ST as far as I am aware can have two external drives as there is no daisy chain on the FDD circuit.

The internal drive gets both D0 and D1, I assume thats so you can copy from Floppy A to Floppy B by swapping disks..

External only gets D1 - so somehow its checking if there is an external drive if so use it as D1 and internal as D0?? is that what SoEL is for??

But in the way we are doing the MOD.. we are now supplying both drives with D0 and D1?? .. until I get to the drive itself.. where I can flip the signal to DS1 via the jumpers on the drive. SO the drive will ignore the D0 signal now???

This must be why I am not an electronics engineer.

James

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Re: Drive swap on STe without cutting pins/tracks

Postby tzok » Fri May 03, 2019 6:25 pm

Bikerbob wrote:The internal drive gets both D0 and D1, I assume thats so you can copy from Floppy A to Floppy B by swapping disks..
No, disk swapping in single drive machines is done completely by software, DS1 is never active there.

According to the Shugart standard there are 4 drive select lines routed to all drives, but each drive reacts only to one DSn signal. This signal is chosen using jumpers or bridges on the drive PCB.

On PC there are only two DSn signals (but there is also a separate MOTOR ON signal for each drive), and usually both drives are set to DS1 (so active signal on DS1 pin enables the drive), but due to ribbon twist DS0 signal goes to DS1 pin. Drive doesn't care about remaining DSn signals, they are not connected. Only DSn signal (pin) chosen by the DRIVE ID jumper is connected to the circuit. All other signals are shared among all drives in the chain. So the jumper/bridge on the drive just route the Enable signal from appropriate pin on the Shugart connector to the Chip Enable input of the drive controller IC.

DSn signal are nothing special - just on/off, so it doesn't matter if you will connect DS0 signal to DS3 pin on the floppy, as long as the floppy will be set ID3 it will recognize this signal and act as DRIVE 0.

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Fri May 03, 2019 8:30 pm

ok, so next chance I get.. I will wire in the drives D0 and D1 jumpers into my switch and try again.. fingers crossed.

James

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Sat May 04, 2019 3:39 am

OH well.. looks like I pooched the drive somehow.. not sure how.. guess when its that old.. connecting and disconnecting can hurt.. Now the drive only works intermittend

:(

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Re: Drive swap on STe without cutting pins/tracks

Postby deltamc2000 » Sun May 05, 2019 3:42 pm

Finally got around to trying this mod out, starting with a selection of early STF, nice and simple to mount the header pins.


3 of these STF (big button) floppy drives (Chinon 347 rev A) are hardwired to be DS0. Irritatingly, there are solder pads for DS0 - DS4, but by the looks of it, DS0 track leads to a wire on the other side of the board that jumps to a IO chip pin. I am going to add some pins, but I suspect it will still send DS0. Could try and cut the wire and jump the DS1 to it, but its a long shot and I have found a few people complaining about this particular model being hard wired.

If I start the Atari up with W2 pin 1 & 2, the internal drive starts trying to read the disk, it seems that the fact is DS0, the external floppy does not boot. If I remove the power from the internal drive, the external boots fine. This tells me the mod is working.

I understand that I cannot use the internal drive when booting from the external drive with no option to DS select, but I hoped that W2 2&3 would still allow a boot. With the sound chip version, I can do the swap without using the internal floppy,

One other option would be to cut the power to the internal drive while, which will loose internal floppy support via switch, at least the option of booting from a Hxc or PooTek.

Anyone have any hints on how to get around this? on the 4 wire power cable to the floppy, cut the 12v and add to the switch when its on W2 pin 2 & 3?

Thanks guys

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Mon May 06, 2019 6:54 pm

Not tried it on an STF. Cant help with that. But I thought of cutting the power as well. because if I route the jumpers one way or the other both are on.. if I turn off the internal.. then the external just works as A.

James

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Tue May 07, 2019 4:56 am

Well, on my Mega STE, I have got the external Gotek working.. but in order to do it I had to kill the power to the internal drive.

If I leave the drive on, and have it set to Drive 2 it still operates.. drive 1 the external also operates.. and the real floppy drive head will move and I am thinking that cant be good. If I switch back to internal drive as A: with external gotek attached, no reads.. unplug the external.. works fine..

Ideas?

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Re: Drive swap on STe without cutting pins/tracks

Postby scsilord » Tue May 07, 2019 6:39 am

The way I got swappable drives working on MEGAST and MEGASTE was to separate and cut the DS0 wire in the ribbon cable.
And then i got creative by having 2x 3-dipswitchblocks. #1 with DS0, #2 with DS1 and let them switch between the cut ribbon cable and the 2 external DS's.

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Tue May 07, 2019 12:01 pm

Disassembled the floppy ..blew through it and we are working again. I have the external drive working as drive A with w401 and w402 pins 1-2 connected and also internal drive ID set to 1....but the internal is receiving all the same signals and I can see the heads move etc. So all I am doing is sending signals to both drives not one or the other. I can pull the power on the internal.. still have the ribbon cable connected and the external works fine. If I have the external connected to the machine with internal set to d0 or drive A I get 4 bombs-external power on or off.

So scsilord your saying you did not play with the w4 jumpers at all? I wonder if I do the w4 jumpers the way I am.. and instead of trying to set ID on the internal I do like you did and disconnect the d0 in the ribbon ..and the d1 going to the external. From the bomb issue I am having it would seem in the default setting I am getting the d0 signal to the external as well.

James

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Re: Drive swap on STe without cutting pins/tracks

Postby scsilord » Tue May 07, 2019 12:41 pm

I have never actually checked if the drive heads move simultaneously. I did notice that the drive motors spin together and with 2 goteks A and B, that both displays update the current track and disk side. I will check if the heads all move at the same time or not.

I slapped some arduino jumper wires on the W4's so i have the DS0/1 from controller and the 2 DS's to the connector available on wire, now i have free reign to set what goes to the 2 external DS wires and the cut internal ribbon.
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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Tue May 07, 2019 7:07 pm

Thanks for the attempt scsilord, but that diagram confuses me a bit more.. lol

The internal floppy gets both D0sel and D1sel to pins 10 and 12 respectively ALWAYS.

W401 and W402 as stated before, only control the external port.

The 14pin external port Pin 5 and Pin 6 seem to be the D0sel and the D1sel.

I can try an external floppy.. because I have one to go with an STF I have. I wonder if I will get 4 bombs with that?

I agree The key is the pin 10.. when I move D0sel to to pin 5 of the external.. I need to kill it from the internal or they will both operate at the same time.

The only thing I am not understanding is the Gotek SHOULD just operate as a B: drive in the Default setup no??? if so.. why am I getting 4 bombs.

James

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Re: Drive swap on STe without cutting pins/tracks

Postby tzok » Tue May 07, 2019 8:00 pm

If the Gotek is installed as internal drive, and there is no external drive configured as drive 0, it has to be set at ID0. Also please notice the location of pin1 on Gotek. Everything is explained in my first post in this topic, please read it carefully. Gotek is no different than a regular FDD.

The easiest method to swap drives is to cut two pins of YM responsible for issuing DnSEL signals and cross them via the switch. My method requires switching 2 things at once: a) signal sent to the external floppy, b) jumper on FDD. Result is the same. If one drive is internal, pin 6 on external FDD connector should be always high, and is not used. You should switch only signal on pin 5 between D0SEL and D1SEL, and on the same time you have to switch an internal FDD to react on the opposite signal.

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Re: Drive swap on STe without cutting pins/tracks

Postby Bikerbob » Tue May 07, 2019 8:27 pm

I tried you method Tzok, it did not work for me. changing the jumper on the FDD did nothing. Sorry I followed your post and it did not work for me on my Mega STE.

you say if one drive is internal.. then pin 6 should always be grounded. SO you are says W401 - AS LONG AS THERE IS AN INTERNAL DRIVE.. should stay in the 2-3 position.. and only W402 should switch.

This still does not prevent the internal drive from receiving the D0sel when I want to use the external drive as D0sel my observations show that I am running the internal drive the same time.. with a Gotek this is bad.. because it is not a std drive with 40/80 tracks etc.. the first time this happened to me it tried to run the head right off the rails.

James


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