Symptoms: mouse stops moving or jumps around or stalls.
I’m on a Mac Mini, and the Logitech M310 mouse stopped working. I went through the usual troubleshooting steps:
- Replace the battery with a fresh one. Result: no change.
- Try using a different surface. I changed from paper to the inside of a security envelope. Result: no change.
- Try to re-pair. It didn’t re-pair, but it still partially worked.
- Tried to pair a different M310 mouse with the receiver. It had been paired before. However, it had the same symptoms as the first mouse. (First clue it’s the receiver or the radio.)
- Rebooted the computer. No change.
- Tried to use a different receiver. The new receiver had some pairing problems.
- I tried moving the mouse closer to the computer, and it paired! This was a big indicator that it was a radio problem.
At around #3 or #4, I messed around with the mouse optical sensor, blowing into it to remove dust. While this seemed to help, it also didn’t fix the problem. So, some dust may have interfered with performance, but this was not the issue.
However, I did notice something extremely strange – and it remained consistent – if I moved my fingertip over the sensor, the mouse pointer moved smoothly.
I tried using other parts of my body, like my arm, thigh, and palm as a mousing surface. They all worked better than paper, but none were as smooth as my fingertip.
Why was the fingertip the best surface? I suspect three things:
- Heat – more heat at the fingertips. The mouse uses an infrared light.
- Distance – the fingertip gets closer to the sensor.
- Texture – the fingerprint is a rough surface.
It still didn’t explain why the fingertip worked, while paper utterly failed.
Getting back to the symptom list about radio: this fingertip fix/failure felt very “digital” to me – the signal works great, or fails completely.
So I first shut off all other 2.4Ghz devices under my control, except one WiFi signal (which is probably 5Ghz).
- Put phones into airplane mode.
- Unplugged the WiFi signal booster.
This didn’t change the mouse behavior. So maybe it wasn’t interference – or the interference is coming from outside of my control, which is possible. (Perhaps a radio tower is beaming microwaves.)
I then put the mouse different distances, and tried to mouse on a cardboard surface. It worked!
On a pebbled cardboard notebook cover, I could get the mouse working around 1 foot from the Unify receiver.
Using my finger, doing the same distance test, I could mouse around 3 feet away from the Unifying receiver.
If distance changes, the quality of mouse motion changes. If it’s closer, it works, and if it’s farther away, it fails. I think this points to radio reception as the problem, and interference as a likely cause.
So, why this discrepancy between the fingertip and the cardboard?
Getting back to “digital”, I suspect that the mouse is doing some image processing to determine direction and velocity. It’s not sending images over to the computer. It sends position and/or velocity information.
So, I started to think about how to determine how much data to shoot over to the computer.
I think the fingertip probably causes the mouse to go into a mode that sends more data.
I tested this idea by mousing from my fingertip to my palm – the mouse worked across the entire surface.
When I started on my palm and moved toward my finger, it didn’t work at all. (I eventually got it working by moving the mouse closer to the computer.)
My best guess is that, when I started with the fingertip, it assumes I am mousing on a detailed surface, and sends more data. Though the signal is experiencing interference, enough data gets through to the receiver that you experience smooth movement.
When I started with the palm, there was less detail, and maybe it was blurry. So the mouse adapted to a lower-detail surface. It might be sending less data over to the receiver, and even less gets through.
Now, I may have this completely backwards. It could be that the fingertip is interpreted as a rough, shiny, bumpy surface with less detail. It may resort to a different way of detecting motion, based on how light bounces off a round surface.
Whatever the case is, I have a strong feeling that the fingertip produces more data, and thus, overcomes problems with 2.4Ghz signal reception.
I also have a strong feeling that the mouse implements different motion detection techniques based on the “mousepad” surface.
I have no tools to detect radio signals in the 2.4Ghz band, so I cannot definitively say that interference is the problem.
However, I feel I’ve eliminated following as problems:
- The computer. (It works with the Bluetooth trackpad.)
- The receivers.
- The mice.
- The batteries.
- The surface.
That leaves radio interference as a possible problem.
What’s the Solution?
Use a corded mouse.
I’ve already wasted an hour on this problem. That’s more than the cost of a corded mouse.
I’d also consider using a corded keyboard again, though it’s hard to find one that uses scissor switch, laptop style keys.
Another, funny, solution would be to get a USB extension cable, and put the receiver closer to the mouse (or keyboard).