Keyboard debouncing

If you're having problems with the hardware of a DM42, post about them here.
reavy
Posts: 21
Joined: Tue Feb 06, 2018 8:08 pm
Location: Phoenix, AZ

Re: Keyboard debouncing

Post by reavy » Sat Feb 24, 2018 8:32 pm

I had this happen with the ‘2’ key immediately out of the box. It’s definitely not an auto repeat issue because I got two 2s with one press of the button, no delay at all.

It has only happened once and only with the one key, but unfortunately it’s cost some of my confidence in the machine, and I am careful to validate my inputs visually rather than only trusting button clicks.

toml_12953
Posts: 433
Joined: Wed May 03, 2017 5:46 pm
Location: Malone, NY USA

Re: Keyboard debouncing

Post by toml_12953 » Sun Feb 25, 2018 6:41 am

reavy wrote:
Sat Feb 24, 2018 8:32 pm
I had this happen with the ‘2’ key immediately out of the box. It’s definitely not an auto repeat issue because I got two 2s with one press of the button, no delay at all.

It has only happened once and only with the one key, but unfortunately it’s cost some of my confidence in the machine, and I am careful to validate my inputs visually rather than only trusting button clicks.
I have one button (X< >Y) that clicks just like the rest but nothing happens unless I then press just a little harder. Then X and Y are swapped as they should be. I can't rely on the tactile feedback for that key. Unfortunately, it's in the middle of the matrix so I'd have to peel back a lot of membrane to get at it. The chances I'd mess up another key are great!

Addendum: Fool that I am, I tried the peeling back anyway. That sheet is tough stuff! All the domes stuck just where they were and the contacts under the X<>Y dome looked fine. No foreign material or anything. All the domes look dead center over their contacts. After I put the calculator back together, the X<>Y key seems to work a little more reliably. Of course that could be either me subconsciously pressing that key just a little harder or wishful thinking on my part.
Tom L

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kintekobo
Posts: 1
Joined: Thu Jun 28, 2018 12:35 pm

Re: Keyboard debouncing

Post by kintekobo » Tue Jul 03, 2018 11:01 am

Following on from the posts here I am inclined to agree that there is something in the software that is causing the keyboard problems. I have just received my DM42 and while trying to follow along with some of the examples in the user manual I found it quite frustrating that what I was typing in wasn't the same as was appearing on the calculator.

I ran a rather long and boring test where I pressed every key at a rate of about one press per second for about 60 seconds each and observes the result. I was getting missed keystrokes and/or multiple presses on just about every key at some point. It seems to me that the missed keys are most likely because the processor is busy on another task and miss the interrupt since I was very careful to make each press identical The multiple keys are most definitely due to some form of key bounce since I have it on slow repeat.

I haven't noticed any key fail to register or multiple trigger on my DM41L which makes me wonder if there is a difference in the keyboard matrix or the code used to implement the keyboard routine that could point to the problem. As it stands the DM42 is very difficult to use as it behaves erratically and can be very frustrating to use.

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