The Sinclair QL Forum

I finally got an Atari compatible mouse to try out with my custom cased QL having previously tried 2 different ps/2 mice with at Atari to ps/2 adapter (neither of which worked).

The 'proper' Atari mouse is much better, it basically does all it's supposed to do in terms of direction and function. However, the cursor seems to jump around a bit, sometimes to the other end of the screen but mostly just up/down/left/right a few rows at a time, which is a bit annoying. The innards of the mouse are spotless.

Is this likely to be something to do with the connections to the Qimi add-on (which I will of course investigate) or are there any other known problems that may cause this that anyone can remember?

My brain is like a sieve, but according to my own article https://www.kilgus.net/2017/01/30/of-mi ... stly-mice/ I had to add pull-up resistors to my mouse interface to get rid of the jumpiness.

Very interesting, thanks. My mouse comes apart quite easily and there appears to be enough room inside to add pull-up resistors under the pcb between the +5v and the XA, XB, YA, YB. I can't damage anything in doing that, can I? I'm not all that qualified but I imagine the Qimi works in about the same way as your SuperQBoard setup?

Normally QIMI has these resistors, but maybe there are different revisions or whatever, I don't know. Having a second set of pull-ups (10k or more) is not a huge problem, so you could just try. Or at least check if the pins are pulled up to 5V without any mouse attached.

Ah, looked at the schematic again, apparently QIMI only has pull-ups on two of the 4 movement lines So chances are this could really help.

Thanks very much!

This is what I've knocked up:
It all fits perfectly on the solder side with the mouse back together. I popped a bit of insulating tape on just in case, and rather conveniently the 4 movements wires were all in a row and right next to the +5v. I'll give it a try later today.

(if the resistor colours aren't clear, they are all 4.7k ohms)

Looks good enough And 4.7k is okay I guess. And, did it work?

No, still the same!

Chr$ wrote:No, still the same!

I've had similar problems. The first (sudden movement of pointer to display extremes) was due to a flakey moulded 9D connector on the lead of the mouse - the socket clasps were too weak, so the connection was unreliable. The solution was to cut it off and use soldered socket.

The other problem I had was with a Zydec Atari ST replacement mouse with Aurora QIMI. The pointer would occasionally move slowly on its own (very freaky). The Zydec mouse lead was very long so I tried extra pull up resistors, decoupling capacitors etc. but nothing stopped it. The final solution was to wind the mouse lead through a 1 inch ferrite torroid near the socket. It's been OK with that for the last 20 years.

Edit: replaced Zytec with Zydec

Good tips, thanks. I did wonder if some of the pin holes on the plug may have been a bit loose when I was checking what went where on the mouse PCB. I'll replace that first and see how it goes.