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David

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Joined: 13/10/2025
Location: Australia
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Posted: 01:20pm 27 Oct 2025

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hitsware2

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Posted: 01:27pm 27 Oct 2025

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David said

You may have inadvertently used invisible ink .

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David

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Joined: 13/10/2025
Location: Australia
Posts: 11

Posted: 01:38pm 27 Oct 2025

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I have come across an odd issue and was wondering if anyone might shed some light.

I am using a CMM2 G2 V2.

A short while ago I attempted to edit a short programme with a “Print @“ statement, but when I press the Shift 2 to get the @ symbol I instead get the “ symbol printed on the screen. It’s seems these 2 keys have become transposed. They work at their correct jobs, just on the wrong keys.

I tried power off and on, tried the reset button, tried an Option Reset, tried shorting pins 40 and 39 on startup.

I was working on a simple 6 LED Chaser sequence programme with a RaspberryPi 40 pin header plugged into the GPIO port. The programme does as it should, the LEDs flash as they should, but when I attempted an edit to insert a Print @ command it went odd.

Changing keyboard and/or removing circuitry has not made a difference. It’s like the keyboard has been remapped.

Any ideas?

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BarryH

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Joined: 05/01/2025
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Posted: 01:47pm 27 Oct 2025

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BarryH

David

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Posted: 01:52pm 27 Oct 2025

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OK, ignore the above problem.

I actually sorted it out by reinstalling the keyboard with the “Option USBkeyboard US” command.

But why did it happen in the first place?

Could using the GPIO port have anything to do with it?

At least next time I will know what to do.

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hitsware2

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Posts: 734

Posted: 08:16pm 27 Oct 2025

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David said OK, ignore the above problem.

I actually sorted it out by reinstalling the keyboard with the “Option USBkeyboard US” command.

But why did it happen in the first place?

Could using the GPIO port have anything to do with it?

At least next time I will know what to do.

"option" was not set US ?

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David

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Joined: 13/10/2025
Location: Australia
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Posted: 11:15pm 27 Oct 2025

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hitsware2 said

said

"option" was not set US ?

The keyboard option was originally set to US, and all has worked fine until last night when doing an edit with a Print statement I found the @ and “ transposed. I don’t recall doing anything remarkable prior, like flying a kite in a thunder storm or waving a sacrificial chicken over the keyboard. One minute all was good, then next edit the keys exchanged addresses.

The only out of the norm was having the GPIO plugged into a bread board and sequencing a pile of LEDs.

However, as I mentioned, the resetting the keyboard to US fixed the issue.

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PeteCotton

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Joined: 13/08/2020
Location: Canada
Posts: 575

Posted: 11:30pm 27 Oct 2025

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I believe your keyboard setting is retained by the small watch battery on the board (I could be wrong about that). But if it is, then did that possibly get knocked and break contact?

Certainly having the " above the 2 key is the UK keyboard layout.

David

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Joined: 13/10/2025
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Posted: 09:33am 29 Oct 2025

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Interestingly, last night I plugged my breakout cable and breadboard with the LEDs to do some further development on my LED sequencing programme, and a short while into editing it the problem of the transposed @ and “ symbols reappeared. However, this time I could return it back to the US keyboard layout without the panic.

So, not sure why, but it seems that a problem occurs that upsets the set keyboard when I plug my electronics in.

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Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 8256

Posted: 10:14am 29 Oct 2025

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Also, if you can it would be interesting to test the battery on the board (don't take it out). If it's approaching 2V6 then it needs replacing as they tend to die around there.

IIRC the CMM2 doesn't store settings in flash, unlike the Pico. You are dependent on the backup battery. I'm sure someone will correct me if I'm wrong - I've not played with a CMM2 for ages.

Another thing, make sure that the CMM2 and external electronics only share a common GND (not a supply rail). It's also a good idea to put a 470R or 1K resistor in series with any GPIO pins if you can. The CMM2 *must* have a solid supply voltage and won't tolerate poor supply cables.

If pin 40 of the GPIO port has a capacitor to GND it will look like a RESET signal and the whole system will reset. It comes as a surprise. It's a good idea to avoid this pin if you can.

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

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