Micromys V5 Intermittent Functionality

Amiga 500

I've not been using my Micromys V5 very much, but now that the system I built for it is complete, and I'm using it regularly, I've noticed an intermittent problem.

1 out of ever 3 power cycles roughly.

On power-up, once the Amiga has finished loading Workbench, the pointer is found in the top left corner of the screen.

As soon as I try to move the mouse, the pointer moves to the top right of the screen, and pretty well stays there...

I mean... if you play with the mouse, scroll the scroll wheel, etc... you can get the pointer to jump to to the left a bit, but it goes back to the top right soon after.

Initially, I thought...maybe it's not auto detecting the computer 100% correctly, so I moved the Micromys V5 jumpers to the 'Amiga' position

Based on information found here -> http://wiki.icomp.de/wiki/Micromys_V5

But that didn't solve the issue..

Then I thought...maybe the mouse connector (DB9) on the motherboard was worn or damaged, I got lazy and just swapped the A500 motherboard.

But that didn't solve the issue.

Sometimes, I can just unplug the Micromys V5 and plug it back in and the issue goes away

But that's not a solution

When the Micromys V5 'works' at startup, it stays working fine, I've not seen any issue appear after starting up successfully..

If I unplug the Micromys V5 when its malfunctioning at start-up and plug in an original Amiga mouse, the pointer works properly.

I don't experience any weirdness using the original mouse...ever...

Any thoughts on why I'm seeing this odd Micromys V5 behaviour ?

I whipped up a little DB9 adapter to make getting the probe clips on easier

Equipment

Result

4.98V DC

Now...there could be a tiny loss due to the 3m of probe wire and the pinch probes and the DB9 connector...
But it's a pretty good rendition of +5V DC

The power supply in this case is just below the multimeter.
Despite its appearance, It is not an ATX PSU, and it has independent switch mode supplies for +5V, +12V and -12V rails, as well as ample capacity (10A on the +5V rail)

I have the same trouble when I use an original Amiga PSU to power this system.

The A500 has an Indivision ECS V2, ACE2b, Lyra3 and ACA500+, running OS 3.2, not sure if any of those 'variables' could be contributing ?

Truth be told...it's far more an iComp computer than an Amiga at this point

Okay...I'll make an adapter that goes in between with the Micromys loading the line

Okay, so I made a pass-through to measure the voltage

Setup

Results

4.83V DC

Please keep in mind, you asked me:
"Do you have a multimeter so you can measure the 5V at the joystick port?"

The most immediate interpretation of that is:
"Please stick your multimeter probes into the joystick port and measure the 5V rail"
which...does imply no load, but there we go..all fixed.

I am happy to build jigs, and measure things, and wheel the lab up here if need be.

While I disassemble to take more pictures.

4.98V - 4.83V = 0.15V

0.15V / 4.7R = 31.9mA (ignoring connector losses)

What is the expected load of the Micromys V5 contraption ?

Mouse being used is Adesso HC-3003PS, just in case "that's a thing"
I mean ... I suppose the mouse itself could wake up on the wrong side of the PS\2 bed and something goes wrong there..

Unfortunately, I only have one PS\2 mouse....
{adds second PS\2 mouse to shopping list}

Quote from Jens

I'd like to see the grounding/shielding efforts before I do any more support work here.

Okay, totally willing to help on my end.
I've completed a full tear-down and reassembly taking a hundred or so photos of areas of interest.

Your request is 'open ended', there is no way for me to definitively answer, but I'll do my best by showing some of the grounding and shielding and if there is a more specific aspect you'd like to see, I will change focus to that.

Edited, factory lower shield

Factory insulator

Board-in connector shield screws

Star-Topology grounds wires connecting A500 Logic Board and Indivision ECS V2 to the ground at system power entry.

forum.icomp.de/core/index.php?attachment/2384/

Quote from Jens

and while you're at disassembling anyway, why don't you launch the system without the case, just with a normal A500 PSU

"I've completed a full tear-down and reassembly"

Umm...it's all back together again...and funny...did the 'odd' mouse thing described above on first boot

I'm away house shopping today, but "I'll be back"

How about this?
I have the first A500 board, the one where I first saw the issue...
I can stuff it back in it's ugly old plastic coffin, with a second Indivision ECS V2 and a second ACE2b.
Alas...I don't have a second ACA500+ ... so I'll move this ACA500+ and this Micromys over and whip out my decrepit Amiga power brick.

Having already seen this behaviour with the Micromys on that board, using the described setup, I'm reasonably confident "the walk" won't be for nothing, as the odd behaviour is sure to show up...

For a couple of months, this system ran on my desk like this; while I waited for the CM1500 case to show up...

Powered by the stock power supply...
And I never said a word about the mouse, because, who's gonna show a picture of a system running like that and say "Help me Obi-Wan"

I'd point out that the ACA500+, ACE2b and Indivision ECS V2 have been 'otherwise happy' to live in the case and consume the power that I've provided them...old A500 plastic box, logic board screwed into an A500 bottom shield, new CM1500 case, old Commodore PSU, new PSU made by me, they all worked the same. Having looked at the support history of all the iComp designed contraptions involved here, the Micromys does not seem like it should be anywhere near the 'weakest link'. There are so many other iComp contraptions in this setup that are sensitive to power, shielding, grounding, that they would likely be going haywire, if there was such a problem.

"Fault Isolation" is indeed a good diagnostic practice, but it can also lead to reduction to the absurd if you let it.

I'm going to get a couple other PS/2 mice and start there, because I think that really would be the simplest thing first.
If it turns out it's the mouse, my best guess is it's protocol related, I'll send it to you, so you can see what it does differently, and maybe increase Micromys compatibility with what's available on the market...which isn't a whole lot these days.

If the problem continues with other mice, then I'll proceed with the second A500 in a plastic box as outlined above.

Chat you in a couple days

Good news,

I ordered a couple alternative PS/2 mice from Amazon.

For the last couple days, I've been using a:
Make: Perixx
PERIMICE-209
Part: M-868

So far, I've not seen the 'odd' mouse behaviour...which is great as that was getting frustrating
I'm going to try the Adesso PS/2 mouse on an older Windows machine over a week, and see if I can get it to behave 'odd' at start-up. I feel obliged to help narrow down if this is simply a defective mouse or possibly a Micromys V5 compatibility issue with that mouse at startup.

Yeah, sure, wear-out is a thing, but it's three months old, the problem's been there since it was bought new.

So statistically, lower probability of a wear-out, though still fully possible, bath-tub curve and all that.

As it still could be a bad wire or contact, I'm testing it on a Windows machine, to see if it is the mouse or the interaction with the Micromys V5 that is the issue.

I can build a PS/2 connector test jig to test the idea of a wire being disconnected or high resistance at power-up,

and we should see a similar 'odd' behaviour, though I can't imagine such a mechanism.
That doesn't mean that all of reality is within the scope of my imagination. Testing is better.

Right now...I'm thinking:
Either this mouse is very sensitive to the PS/2 supply voltage requirement of +4.5V <> +5.5V
It's cord is extra thin, so it may suffer meaningful voltage loss over 30AWG wires and the Amiga's 4.7R internal resistance.
So maybe it's not POR'ing correctly ?
Or...

It 'needs something' at power-on \ initialization that it's not getting from Micromys V5.

and as a result it's sending back data that makes no sense, or is not synchronizing with the Micromys V5.

Found someone online talking about the trouble they have had with ensuring that their PS/2 mouse driver is synchronized with their mouse:
"The trick i found to fix this is to use the fact that byte 0 is supposed to have bit 3 always set. So when i receive a byte that is supposed to be #0 with bit 3 cleared, i simply discard it and assume byte 0 will come next. As long as you're on synch, this is completely transparent, and when the mouse comes out of synch, only a few events are sufficient to restore synchronization (especially fast with steady clicks)"

Not aware of what Micromys V5 does to detect and correct out of sync condition, or if it uses PS/2 mouse streaming or a different mode of operation.

I started with a good old probing of the solder joints back to the PS/2 connector, looking for shorts or breaks in the cheap wire.

For sure this mouse is made in China, like 80%+ of all electronic goods.
China is the worlds 'preferred' factory and they have the greatest collective manufacturing experience of any nation.
But we can all pretend, I guess, that only badly made things come from there, if that smoothes over our egos.

It uses the dirt cheap KA2B optical sensor, which complies with the following spec:

Absolute Max is also 5.5V

It has a built-in regulator with 3.6V I/O output, so it may not like being voltage starved, like some of iComp's own devices.

POR is not specific to micro controllers...

Your FPGA NOR configurator, NAND flash and DRAM all have POR circuitry, as will this optical mouse chip.

I'll keep digging until I have a believable failure mechanism.
I'm not confident this mouse is innocent, heck, that optical chip sells for $0.10 in low volumes, so we know how much testing it got and the mouse assembly is about $20, so we know how much testing the whole system got. But that does not mean it's defective, just not vetted, and it can be tested in the field.

I would, at the very least, like to save others from buying a widely available PS/2 mouse on Amazon,

if it's going to cause them the very same grief.

I assume you'd like to save your customers the same.
So, I'll stay on it for a bit, see if I can root cause it.