09538: mac128k, mac512k: keyboard occasionally auto-repeats phantom character(s) with no key held

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
09538	DIP/Input	Minor	Random	3 days ago	19 hours ago

Tester	Marcher	View Status	Public	Platform	MAME (Official Binary)
Assigned To		Resolution	Open	OS	Windows (x64)
Status [?]	Confirmed			Driver	apple/mac128.cpp
Version	0.288	Fixed in Version		Build	x64
		Fixed in Git Commit		Github Pull Request #

Summary	09538: mac128k, mac512k: keyboard occasionally auto-repeats phantom character(s) with no key held
Description	On mac128k and mac512k, at an unpredictable moment with no key held down by the user, the emulated keyboard spontaneously begins auto-repeating a character (or a short, fixed cycle of several characters) as if a key were stuck down. This is not triggered by any user input - it has been observed to start while the machine is sitting idle (e.g. with the Key Caps desk accessory open, or a terminal window in the foreground, no typing in progress). The glitch stops as soon as any other key is pressed, but can recur later at another random interval (observed gaps between occurrences range from under a minute to many minutes; it does not reproduce on every session, and can fail to reproduce for many minutes of idle waiting even on an affected machine/software combination). macplus was tested under the same conditions and did not reproduce the issue.
Steps To Reproduce	1. Start mac128k or mac512k with any bootable System floppy. 2. Bring up a state where the keyboard is idle and no typing is in progress - e.g. open the Key Caps desk accessory, or simply leave a terminal application (MacTerminal 1.1 in my testing) in the foreground. 3. Do not touch the keyboard. Wait - anywhere from under a minute to several minutes. 4. Observe: a character (or short fixed sequence of characters) may begin appearing/repeating on its own, at the machine's configured key-repeat rate, with no key held. 5. Press any other key to stop the repeat. The glitch may recur later at another random interval. This is intermittent; multiple attempts and idle-wait periods may be needed to reproduce, and it will not reproduce every time even on an affected configuration.
Additional Information
Github Commit

Flags
Regression Version
Affected Sets / Systems	mac128k, mac512k

Attached Files

No.24629 Robbbert Moderator 3 days ago	Unfortunately it appears that the only bootable system disk is "sys11", and it doesn't contain notepad or any kind of application for typing. There's other system disks, but they are rejected as unknown format by MAME's internals. So I'm not able to confirm your issue.
No.24633 Marcher Tester 3 days ago	I booted from sys11, and it does contain all the desk accessories, including Note Pad and Key Caps. Furthermore, these programs aren't required; just click on the file/disk name within the system, and you can change them (I was able to reproduce the bug even in this filename change field). I'm currently testing the reproducibility of the bug on this (sys11) system and will edit this report as soon as any updates are available.
No.24637 Marcher Tester 3 days ago	I tested the reproducibility of the bug on sys11 and got a positive result. Due to the random nature of this issue, I can't yet provide any definitive information on how to reproduce it with 100% certainty. I ran 20 startups, and in two of them, the bug appeared from the very beginning: the "]" characters would repeat in the floppy disk name field (when booting, the system floppy disk is highlighted as selected, allowing you to change its name with keystrokes). Also, in three of the 20 startups, this problem recurred when opening Control Panel. I then left five MAME sessions running with the Key Caps application open. In four of them, the "]" characters would repeat at varying intervals for 30 minutes. When I deleted them, they would repeat again after a while, as if the "]" key had been pressed. At the same time, in a couple of cases, when I double-clicked text (from numerous "]") in the Key Caps field and pressed Backspace to delete it, the field itself began to fill with "1" characters. I apologize for giving so little detail.
No.24642 Robbbert Moderator 2 days ago edited on: 2 days ago	I clicked on System Disk and erased some of the letters, then I opened the disk and ran the Font Mover, decided it wasn't for me and clicked Quit. The name of the disk filled up with ] character and an error appeared about the name being too long. Clicking OK just made that message keep coming back in an endless loop, making the system unusable. So, it's confirmed.
No.24658 cuavas Administrator 1 day ago	That’s an awful lot of text to say you don’t understand what’s going on at all. The keyboard MCU watchdog can’t be triggered by the host failing to read the keyboard data from the VIA. It triggers if the MCU gets into a state where it isn’t scanning the key matrix. That has nothing to do with this. The phantom stuck key (usually closing bracket) happens when MAME’s scheduling timeslices cause the microcontroller in the M0120 keypad to miss signal transitions from the microcontroller in the main M0110 keyboard. This doesn’t happen for the M0110A Mac Plus keyboard as it’s a single unit with one microcontroller that emulates the combination of the original M0110 keyboard and M0120 keypad, so there aren’t two microcontrollers that can get out of sync with each other. You can avoid the issue by changing the slot option to use an M0110 keyboard without a keypad or to use an M0110A keyboard with its integrated keypad. Actually fixing it without seriously hurting performance is more complicated.
No.24659 cuavas Administrator 19 hours ago	Oh, and for the record, the same thing will happen with macplus is you set the slot option for the same M0120 keypad and M0110 keyboard. It's entirely due to the keypad and keyboard getting out of sync.