Q68 New users and general usage thread

[BSJR]

The HP keyboard works OK on my PC, so may be too much power is drawn by the old keys?

Not if your 5V power supply is stabilized and delivers at least 1A as recommended.

This is the first time I ever hear about a non-working keyboard. Especially that mouse was affected is weird - both ports are completely separate electrically and logically, except power supply. Are you sure it was not a mouse/keyboard mismatch?

The PSU claims to be 2A.
The old HP keyboard is rated 500mA max.
The newer keyboard doesn't show any details but another working one says 35mA.
The optical mouse is 100mA but an old ball mouse is only 15mA.
All are original with PS/2 plugs, no converters are involved.
The "mismatch" (HP keys & ball mouse) worked on my PC hardware.

Bob

[Dave]

One quirk of the design of the Q68 is that the 5V input is passed directly to the keyboard/mouse. If the supply is under around 4V or over about 6V the keyboard and/or mouse may not work or may partially work.

A lot of people assume there's a voltage regulator and will use any higher capacity supply that fits, but on the Q68 this is potentially devastating to your keyboard/mouse. It *must* be a 5V supply, and that 5V actually *must* be 5V +/- 10%.

[tofro]

Hmm. I wouldn't necessary call it "a quirk" when a Computer is not properly working with a power supply which is not to specs.

It also will not work from an AC 110V power outlet...

Tobias

[Peter]

One quirk of the design of the Q68 is that the 5V input is passed directly to the keyboard/mouse.

No. It is absolutly normal to expect that regulated power supply, as the manual demands, is regulated.
If not, no USB device or smarthpone could be designed the way they are.

[Peter]

All are original with PS/2 plugs, no converters are involved.

USB-PS/2 converters are no problem, if used with the combo devices they were made for. No point in avoiding those.

The "mismatch" (HP keys & ball mouse) worked on my PC hardware.

I know. I meant if you are sure keyboard and mouse had not been swapped on the Q68 splitter?

I asked, because except power supply, there is no reason why keyboard should affect mouse or vice versa.

If we assume the Q68 does not accept your keyboard, that still does not explain why the mouse did also not work. (If I understood correctly, the same mouse worked with different keyboard on Q68.)

[Dave]

One quirk of the design of the Q68 is that the 5V input is passed directly to the keyboard/mouse.

No. It is absolutly normal to expect that regulated power supply, as the manual demands, is regulated.
If not, no USB device or smarthpone could be designed the way they are.

There's no flaw in your assumptions. There is a flaw in what happens in the marketplace.

Many USB and generic wall wart type adapters give 5V at 1A or 2.1A and well regulated. However, many times more cheap Chinese supplies provide a nominal 5V that is typically 5.5 to 6.5V, and the voltage varying under different loads due to poor design. They also have a fair amount of ripple due to corner-cutting with capacitors.

This doesn't matter to cellphones or devices that use 3.3V or less and that can regulate the noise and excess voltage, but it does matter on the Q68.

This isn't a flaw of the Q68, but of the poor general quality of generic power supplies. Which is incomprehensible, considering good reference designs and component sets cost only a fraction more.

That said, people have years of experience of it being "ok" to use a higher voltage supply because in 99% of cases it's going into a regulator and it just works. On the Q68 this is potentially harmful to external devices, but not to the Q68 itself. This again is no fault of the design, but people not following the manual.

[Peter]

Originally, I was for delivering a known power supply with each board. But Derek rightfully saw the internationalization issues.

There was not a single case of a problem which could be traced to an unregulated supply yet. So I guess Derek made the right decision.

[Dave]

It was the only reasonable decision. It actually changed my design for Issue 8, and I now power it the same way, with the same "provide your own PSU" policy. The only small change I made is including a 5V regulator and suggesting a power supply that delivers 9V at 2A or greater. As issue 8 takes traditional QL expansions, this makes sense. There's no need for it on the Q68.

[Pr0f]

Is there a definitive list of I/O addresses for the Q68 - I know some of them are in the Q68 manual, and I know also that there is a specific address range set aside for the expansion port area.

But given the boot loader potentially allows other ROM images to be loaded, how does one interface to the PS/2 port, serial port and the Screen 1 area control registers for instance?

Would it be possible to publish a full list of the decoded addresses and their function? (pretty please)

[tofro]

Would it be possible to publish a full list of the decoded addresses and their function? (pretty please)

"Use the source, Luke" - http://www.wlenerz.com/smsqe/

Download, find a file keys_q68

Tobias