Micromys v3 problems after 15 minutes of use?

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Don't Panic. Please wash hands.
  • Not sure if it‘s my micromys v3 or what but im finding that after a bit of consistent kb & mouse use, my mouse tracking always seems to go crazy. Mostly on the horizontal axis. Like moving in either horizontal direction will only move the cursor one way. I tried a second ps/2 mouse and get the same results. Only a cold boot seems to fix the issue. This converter is fairly old but I’m not sure if I should buy a newer ps/2 converter (fairly cheap) or just bite the bullet and spend the $60+ on an actual atari st compatible mouse.

  • OK, so the important bit of information is that the target computer is an Atari ST - this is not a common case for any of us. However, the Atari mouse protocol is identical to the Amiga mouse protocol, only with two wires swapped. So for moving the pointer into one horizontal direction, both "horizontal" pins must toggle, meaning that we're not talking about a hardware fault.


    In easier words: If the pointer moves properly into three of four directions, then all four direction signals are fine.


    Next, the pin-swapping compared to the Amiga is between one horizontal and one vertical signal, so if MMV3 suffered from a wrong automatic computer identification, you'd be observing both directions to not work properly.


    To be honest, I'd try a genuine ST mouse first (maybe you can borrow one?) and see if have the same issue. And if so, there may be a piece of software that gets in the way, or the keyboard MCU has a problem that shows after 15 minutes. You may know that the keyboard MCU is passing the mouse information to the main system in an ST.

  • To be honest, I'd try a genuine ST mouse first (maybe you can borrow one?) and see if have the same issue. And if so, there may be a piece of software that gets in the way, or the keyboard MCU has a problem that shows after 15 minutes. You may know that the keyboard MCU is passing the mouse information to the main system in an ST.

    Thank you for the troubleshooting Jens. I had a genuine Atari ST mouse but found it to be extremely sluggish, and since put it into storage, and now I can’t find it. Ugh. Anyway, the only software I use is Notator by c-lab. The problem seems to manifest after doing multiple keyboard/mouse combination commands, like “hold control key and move mouse over the value to sweep values” or “click and drag while holding alternate key” , but I’ve been unable to troubleshoot what exactly triggers the problem. Sometimes I’ll just press a few keys and the problem resolves temporarily. But everything will work fine for a while. Are you saying there is no chance it’s the micromys? I know the Notator program has a built in mouse accelerator. I don’t use any extra startup software or drivers.

  • Are you saying there is no chance it’s the micromys?

    Again, if three out of four directions work as expected, it can't possibly be Micromys. One direction always uses two signals at the same time, and a movement always requires both to toggle in a certain sequence. Only the sequence determines "movement or not", and the order of signals toggling will tell the computer (or in case of the ST: The keyboard MCU) the direction. If you are interested in the technical details, look up "in-phase and quadrature signals".


    I know the Notator program has a built in mouse accelerator.

    That means you know more about Notator than I do :-) Jokes aside, I know that Notator is a MIDI sequencer, and I therefore assume that I'm talking to a person who's talents are more on the musical rather than the technical side. Let me know how deep we should dig - a quick google search found issues with the Notator dongle, and the only time I have ever had an Atari ST on the desk for repair was when the power supply failed (that was a 1040ST with the internal power supply). With the high amount of PSU failures that we see in the Amiga market, I would not exclude that you have a similar problem, just because the computer is of a similar age.


    Further, the keyboard and mouse/joystick connectors must be considered a mechanical part: You move them frequently when pressing keys, and solder joints may be bad after all these years. It may therefore be a simple cold solder joint that makes the keyboard MCU crash, and pressing a few keys brings it back to life - until the next crash or a temperature cycle, which may make contact again. This is just speculation, though.

  • Again, if three out of four directions work as expected, it can't possibly be Micromys. One direction always uses two signals at the same time, and a movement always requires both to toggle in a certain sequence. Only the sequence determines "movement or not", and the order of signals toggling will tell the computer (or in case of the ST: The keyboard MCU) the direction. If you are interested in the technical details, look up "in-phase and quadrature signals".

    I don’t think it’s 3 out of 4 directions working normally. The first symptom is usually any horizontal movement of the mouse (ie left or right) will only move the mouse in one direction. So , for example, I could be moving the mouse left or right, but either way moves cursor to the right. Vertical movement will continue to work for a short time but then even the response on that goes wacky too.

  • So , for example, I could be moving the mouse left or right, but either way moves cursor to the right.

    ...which requires both horizontal signal lines to toggle, hence Micromys is OK.

    Vertical movement will continue to work for a short time but then even the response on that goes wacky too.

    This really sounds like we're looking for a problem within the keyboard controller of your computer. Again, let me know how technical you are, if you have amultimeter and feel comfortable making measurements on an open computer.

  • if the problem was the keyboard controller , then the keys would also have problems? Keyboard is 100% all the time.


    If it was cold solder joints , then things tend to get better when heating up, not other way around? Cold boot tends to fix the problem. Although one time it didn’t until I pulled ps/2 mouse from micromys, and reinserted it. Then it worked again.

  • Just checked the ST keyboard schematics - if the whole keyboard continues to work, then the LS244 chip is the culprit. Exchange that, and your problem is most likely gone. You can also use a HC244 or HCT244 chip, whatever the local electronics store has in stock in DIP20 package.


    The circuit board is only single-sided, so the soldering work is pretty simple - no pump required, I'd start with solder braid to get the old solder off and remove the chip.

  • Just checked the ST keyboard schematics - if the whole keyboard continues to work, then the LS244 chip is the culprit. Exchange that, and your problem is most likely gone. You can also use a HC244 or HCT244 chip, whatever the local electronics store has in stock in DIP20 package.

    Thank you kindly for that information. Is it at all common for these chips to burn out?. Could the chip get confused if being sent information too fast? I remember the original Atari mouse was very slow and this ps/2 mouse feels like 4 times as fast. Could a buffer overflow be causing the problems I’ve described? I was thinking to still buy a native Atari compatible mouse to give it a go before doing this chip change.

  • Is it at all common for these chips to burn out?.

    THis particular one has a connection to the outside world - and that's "evil" in terms of electrostatic discharge. So yes, any chip that has a connection to the outside world is prone to die prematurely.


    Could the chip get confused if being sent information too fast?

    No, speed is not a problem for these chips. It's only voltage outside the range that it can withstand. There are no protection diodes on the keyboard PCB, but the chip is cheap enough not to worry about that.


    Could a buffer overflow be causing the problems I’ve described?

    No. As I wrote earlier, if you're interested in the technical details, you should look up in-phase quadrature signalling. With the keyboard MCU only looking at one edge of the mouse signals, there is a chance that one of the two direction signals being stuck causes the exact behaviour you're describing.


    Also there are many LS244 chips on the ste motherboard. I have no idea which one controls the mouse. It will require more research and maybe a post to the Atari forums. Thx

    You're looking at the wrong board - not the motherboard, but the keyboard PCB is where you need to look for the 74LS244 chip.

  • Interesting that my issue is always after like a period of consistent use. Ie it always works fine in the beginning.

    Static discharge doesn't always blow the chip out completely. It may just result in faults that only show after the chip has warmed up. If you happen to have ice spray at hand (don't buy - too expensive compared to the price of the LS244 chip), you could use it until it fails and then try to make it work again by cooling the chip down - just to be sure that it's really this chip, and not Micromys.

  • yeah I don’t have any ice spray. But you’ve helped narrow down the mostly likely problem!


    MM74HCT244N


    I ordered these at an excellent price along with some dip20 sockets. Hopefully these are the compatible chips and will solve the problem. I’ll still wait for the Truemouse and see if that solves it before I go soldering the keyboard. It looks like an easy procedure, but the last thing I need is to lift a tracing or do something stupid that causes more problems.

    Edited once, last by Jens: (link removed - please don't link to any shop sites, I don't want to deal with the legal implications) ().

  • Two dollars for a DIL-TTL chip is a lot of money, and shipping was quoted really high when I looked at the link (now deleted), but that may be because you've looked for a seller closer to your location (other side of the pond?). I'm aware that times of a "local electronics store" that carries 74-TTL chips are over, and it's "everything online" these days. However, the basic concept of these 74xxyyy chips remains the same: If not operated at/near their limits (which is not the case here), the manufacturer and sometimes even the logic family (LS, HC, HCT or even F) are interchangable, and you won't notice a difference.


    Choosing HCT is the correct thing to do, as it consumes less power, is probably more rugged in terms of static discharge (most of them withstand the 2000V human body model) and they come closest to the switching levels of the LS family - not that it matters on signals that swing at kHz frequencies, but it's good practise :-)

  • Very informative! Thanks. :)

    The price is for 5 chips, so maybe it’s not quite as bad as you suspect.

    I’ll report back in 1-2 weeks with the results of the new mouse and/or chip replacement.

  • oops - my bad :-)


    Yes, please report back. We don't have too many Atari customers yet, and this would be my first-ever-remote-repair of an ST.

    I was shocked when the mouse showed up yesterday, after only one or two days in shipping. But the mystery is slowly unraveling here. Yes, the problem still occurs with the Atari mouse. (A pricy rule out for sure). But then something you said before triggered my mind to start pressing on the keyboard. And Eureka! It seems that when I put any significant amount of pressure just above the number pad, the problem corrects itself. This area is around where the LS244N chip would be, and also the mouse port connectors. So this would lead me to believe that yes, the problem may just be a cold solder joint. Why couldn’t I have tried that last week? <facepalm>. So the conclusion is that micromys didn’t cause the problem. Or did it?! Now that I’m thinking about it, the device never quite fit properly on the underside of the keyboard. I always thought to myself, it’s not really made for Atari ST, because it was always rather forced into position with the black box hardly able to make it out from underneath the front of the computer. I.e. it was definitely putting undue pressure on the mouse port itself. Until I got a DB9 ribbon extension to fix the problem a few years later.


    Anyway I’m not here to blame, and I understand you’re on v5 now anyway. And it may all just be due to old age for all we know. I’ll open her up and check for cold solder joints and that should fix the problem I hope. :)

  • Yes, the cable for Micromys V3 was a bit short for the ST, and we've made it longer for the newer versions. Also, V5 has an option to get a "slim" DB9 connector without the screws on the sides, though that's mainly meant for the Amiga 600 computer where there is just no space for the wider plug.


    That said, we really don't have that many ST customers - maybe because we hardly offer anything else for that computer, or because too many people found that the cable was too short?


    In any case, it seems like you're close to a solution, just by adding some fresh solder to all solder joints involved.

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