using the SDRIVE-MAX in conjunction with other drives

[_The Doctor__]

I saw this but it looks like it's a bit above my paygrade.

nah it isn't... this is a dead simple fix you don't even need the perf board.... it just makes it tidy...

[Mr Robot]

If you think perfboard is overkill...

 

 

 

 

 

In my quest to be 'ok' at PCB design, every opportunity for practice must be taken!

 

 

[Waynetho]

As a matter of fact, all it would take for this mod would be a little bit of adhesive to attach the 74LS07 to the UNO in "dead-bug" fashion (pins sticking up), the resistors and wires attached to the respective pins and insulated, then the unnecessary pins of the chip either folded over or clipped off.

Edited March 3, 2019 by Waynetho

[manterola]

Here is a couple of interesting article about "open collector outputs" and why the concept is useful when dealing with "data buses". And they talk about the 7407. This open collector output I has been "emulated" before in the sio2pc, sio2bt, sio2wifi and many other cases by using a diode. The basic idea behind this is that the open collector ouputs do not "generate" current , they only "sinks" current to ground. That's why diode looks like is in the opposite direction. I am not sure, but I guess some sio2sd present the same problem: the output is not open collector bus compatible.

 

https://www.evilmadscientist.com/2012/basics-open-collector-outputs/

 

https://electronics.stackexchange.com/questions/181952/why-does-the-i2c-interface-use-the-open-collector-open-drain

[djmat56]

A little late to the chat but ive recently got back into my Atari stuff having purchased an Sdrive max. Couldn't get it to work hooked up on the chain with the 1050. Same as other people. The 1050 won't boot with the sdrive connected no matter if virtual disks are empty. Checking inside it does have the diode and latest firmware. All I want to be able to do is use both drives without having to keep disconnecting one and also copy to real floppies from the sdrive.

 

My solution - I soldered a switch between the arduino and the RX/TX wires from the sio and mounted the switch on the back of the sdrive. The sdrive is not powered from the SIO. Now I flick the switch up and I can use the sdrive and flicking it down means I can use the 1050 and all works fine. This also means that I can now copy to a real floppy simply by flicking the switch once the image is read into the Atari.

[TGB1718]

Sounds like your SDrive doesn't have the 7407 buffer chip mods to make it work with other SIO devices

 

Also, I may be wrong, but I thing Lotherik's SIO splitter will do this for you and also allow more devices so you don't need to keep unpluging

https://lotharek.pl/productdetail.php?id=158

 

I have a splitter, but my SDrive also has the buffer, so can't test this theory

Edited April 4, 2020 by TGB1718
Update

[SS]

1 hour ago, djmat56 said:

Couldn't get it to work hooked up on the chain with the 1050. Same as other people. The 1050 won't boot with the sdrive connected no matter if virtual disks are empty.

What happens if you set the 1050 as D2?

[manterola]

The SIO splitter shouldn't make any difference 

[djmat56]

5 hours ago, SS said:

What happens if you set the 1050 as D2?

I haven't tried to be honest. This would mean having to switch it back again everytime i wanted to boot from the 1050 so too much of a pain. I have successfully created a dozen floppies today having both hooked together and using the switch

[ijor]

On 4/4/2020 at 12:41 PM, TGB1718 said:

Sounds like your SDrive doesn't have the 7407 buffer chip mods to make it work with other SIO devices

 

Anybody tested SIO divisor zero (126 Kbps bitrate) with the 7407 buffer? The problem of using an open collector driver is that the higher speeds probably won't work, at least not with computer that has the "infamous" caps on the SIO signals. A diode should have the same effect, I understand?

[TGB1718]

6 minutes ago, ijor said:

The problem of using an open collector driver is that the higher speeds probably won't work,

Why would that be ? the slew rate of this chip is around 20ns, with pull up resistors it operates

in the MHz range.

 

I recently used one of these in my Atari STE debugging problems on the Read data line from the floppy

drive, I put it between the floppy drive and the FDC chip to clean up the signal and it performed very

well indeed and that's a much higher bit rate than the 8 bit SIO.

[+DrVenkman]

15 minutes ago, ijor said:

 

Anybody tested SIO divisor zero (126 Kbps bitrate) with the 7407 buffer? The problem of using an open collector driver is that the higher speeds probably won't work, at least not with computer that has the "infamous" caps on the SIO signals. A diode should have the same effect, I understand?

Normally I run mine no faster than about Divisor 6 for SpartaDOS 3.x compatibility, but I just set mine to Divisor 0 and loaded a game - worked great. 

[ijor]

1 hour ago, TGB1718 said:

Why would that be ? the slew rate of this chip is around 20ns, with pull up resistors it operates

in the MHz range.

The slew rate for an open collector is relevant for the falling edge only, it has no raising edge by itself. The raising edge and the maximum frequency depends on the pullup resistor value and capacitance.

 

1 hour ago, TGB1718 said:

I recently used one of these in my Atari STE debugging problems on the Read data line from the floppy

drive, I put it between the floppy drive and the FDC chip to clean up the signal and it performed very

well indeed and that's a much higher bit rate than the 8 bit SIO.

 

Yes, of course, every ST has an open collector chip at the FDC outputs. But the analog components are designed specifically with this in mind. The Read data line from the floppy has a very strong pullup, 220ohm, and no capacitor. In comparison, the 8-bit machines have 4K7 pullups and most models include capacitors.

 

Besides, it is a fact that even at USD rates, drives already have problems on computers with capacitors on the SIO lines. USD bitrate is less than half the bitrate than divisor zero.

 

1 hour ago, DrVenkman said:

Normally I run mine no faster than about Divisor 6 for SpartaDOS 3.x compatibility, but I just set mine to Divisor 0 and loaded a game - worked great.

 

Thanks. On which computer exactly? Or more important, with or without the capacitors?

 

Edited September 3, 2020 by ijor

[+DrVenkman]

3 hours ago, ijor said:

Thanks. On which computer exactly? Or more important, with or without the capacitors?

My 1088XLD beta machine - no speed-limiting caps on the SIO lines. 

 

In fact, the only machine I owned that those things was a 130XE that I disassembled for parts a few years ago. None of my other machines (all 400s, 800's, and XLs) have them.

[archeocomp]

Shouldnt this type of bus (like floppy) be always terminated with pullup resistor pack at the very end?

[TGB1718]

4 hours ago, archeocomp said:

Shouldnt this type of bus (like floppy) be always terminated with pullup resistor pack at the very end?

Yes you are correct, and they are, using OC outputs with no terminators wouldn't work very well if at all.

 

On the Arduino end of the SDrive they would be set to INPUT PULLUP terminals

 

and the line to the SIO data has it's own pullup as per the circuit diagram.

[ijor]

On 9/3/2020 at 7:29 PM, DrVenkman said:

My 1088XLD beta machine - no speed-limiting caps on the SIO lines.

Thanks. An 1088XLD is not the typical machine, though. But it might be a clue that it is probably ok for machines without the caps.

 

I still think that it has good chances to fail on computers with those caps. I realize that it is always possible to remove the caps. I just think that it should be noted that using an open collector buffer has its drawback. It might be a non issue for some people. Important to be aware about it, nevertheless.

Edited September 6, 2020 by ijor

[+mytek]

Atari probably was forced to put in the caps to appease the FCC and to help protect the inputs from static electricity when a kid slid across the carpet just before touching the computer. Although I have yet to hear of a 1088's Pokey or PIA chip getting zapped.

 

Maybe they should have used capacitors that would vaporize after a couple of weeks of use ?.

 

[Peter Kmet]

If I understand correctly the issue of SDriveMAX blocking real floppy drive is Ardunino-UNO USB-to-serial chip [used for programming] ?