12-12-2024, 11:23 PM
Another update.
After a big push over the last week, new boards have now been ordered.
Hopefully, production ready. We'll wait and see on that one.
One of things I was struggling with, as to what to do, was to do with the keyboard interface.
With the classic microbees, the keyboard was scanned through the 6545 CRT controller. It was a nice, cheap & effective
way to attach a keyboard back in those days. Moving forward though a better solution had to be found with a keyboard
that could be interrupt driven rather than polled. Complex running software sometime doesn't have the opportunity to
pause to see if there is any keyboard activity, so in some circumstances key strokes can be missed.
The 256TC and Teleterm models, and the Gamma all had keyboards that are interrupt driven, and better for it.
However, most of the software written for earlier Microbees, particularly games, rely on scanning the keyboard
through the 6545 screen controller, polling for keyboard input.
On to the new models - the one with the larger 98 key layout actually uses a PS/2 interface internally. The PS/2
interface is available to both the 68000 (MC68SZ328) and the Z80, but also the key scan codes actuate an
8 x 8 matrix that can still be scanned by the CRT controller for legacy software. This is the same approach as used in our PS/2 interface adapter
that can be added to standard & premium Microbees. It works well, and works with all the older software that scans
via the CRT controller.
The prototype of the new model with the 64 key layout still had the keyboard connected to the scanning circuit on the CRT controller
and it worked perfectly, but then this means that the keyboard scanning is different for each of the 2 new models.
So, I bit the bullet and converted the 64 key layout model to scan the keyboard via a PS/2 keyboard controller, and mapped all the keys
accordingly. This means that software for the new machines will work on each model without having to have different keyboard routines.
If you have a look at the photo of the PCB (above) you will see the PS/2 keyboard keyboard controller just above the keyboard section, just
to the right of the middle of the PCB. I've also put in a way for the processor to tell which size (64 or 98 key) the keyboard is.
Of course, the old matrix scanning will be catered for as well, so all the old software will still work.
The new version of the FPGA board is all done & panelized into a 2 x 2 panel, ready for building on the Pick and Place machine.
If all goes well, I should receive the new boards at the end of next week and then I get to prove them out.
Also, the key caps for the 64 key layout are shipping from the US tomorrow. I should have them at the end of next week
as well.
After a big push over the last week, new boards have now been ordered.
Hopefully, production ready. We'll wait and see on that one.
One of things I was struggling with, as to what to do, was to do with the keyboard interface.
With the classic microbees, the keyboard was scanned through the 6545 CRT controller. It was a nice, cheap & effective
way to attach a keyboard back in those days. Moving forward though a better solution had to be found with a keyboard
that could be interrupt driven rather than polled. Complex running software sometime doesn't have the opportunity to
pause to see if there is any keyboard activity, so in some circumstances key strokes can be missed.
The 256TC and Teleterm models, and the Gamma all had keyboards that are interrupt driven, and better for it.
However, most of the software written for earlier Microbees, particularly games, rely on scanning the keyboard
through the 6545 screen controller, polling for keyboard input.
On to the new models - the one with the larger 98 key layout actually uses a PS/2 interface internally. The PS/2
interface is available to both the 68000 (MC68SZ328) and the Z80, but also the key scan codes actuate an
8 x 8 matrix that can still be scanned by the CRT controller for legacy software. This is the same approach as used in our PS/2 interface adapter
that can be added to standard & premium Microbees. It works well, and works with all the older software that scans
via the CRT controller.
The prototype of the new model with the 64 key layout still had the keyboard connected to the scanning circuit on the CRT controller
and it worked perfectly, but then this means that the keyboard scanning is different for each of the 2 new models.
So, I bit the bullet and converted the 64 key layout model to scan the keyboard via a PS/2 keyboard controller, and mapped all the keys
accordingly. This means that software for the new machines will work on each model without having to have different keyboard routines.
If you have a look at the photo of the PCB (above) you will see the PS/2 keyboard keyboard controller just above the keyboard section, just
to the right of the middle of the PCB. I've also put in a way for the processor to tell which size (64 or 98 key) the keyboard is.
Of course, the old matrix scanning will be catered for as well, so all the old software will still work.
The new version of the FPGA board is all done & panelized into a 2 x 2 panel, ready for building on the Pick and Place machine.
If all goes well, I should receive the new boards at the end of next week and then I get to prove them out.
Also, the key caps for the 64 key layout are shipping from the US tomorrow. I should have them at the end of next week
as well.