MTX Pi

[Dave]

Extensive modifications done to MTX keyboard to support separate functions for the reset keys for MTX Pi

keyboard_mod_wire_640.jpg (98.65 KiB) Viewed 37774 times

keyboard_mod_640.jpg (70.85 KiB) Viewed 37774 times

[Bill B]

Dave,

I made three suggestions for modifying the keyboard:

1. Connect the mid point between the reset switches to one of the keyboard drive lines.
2. Add a 21st connection to the mid point between the reset switches.
3. Connect back to back diodes across the reset switches.

If I understand your photos, you have opted for option 2. Is that correct?

I will probably try and support both options 1 & 2 in the software. Probably not option 3 unless there is much demand.

Bill.

[Dave]

Hi Bill,

I wanted to minimise any messing with the original keyboard, so have only made a single connection as shown in the photo, although wired to one of the switch terminals, it is logically in in the middle of the two switches - Option 1. The new connection is wired to DR7, but not on the keyboard PCB, it's done on my breakout board so that I can remove the connection by just removing a link.

regards
Dave

split_reset_640.png (11.28 KiB) Viewed 37770 times

Kbd_mods_640.png (21.27 KiB) Viewed 37770 times

[Bill B]

Dave,

OK.

The point of option 1 is that it could be done with a point to point wire on the back of the keyboard PCB, and does not require a flying lead. Probably neater, although it does require two solder connections to the PCB.

Having bought the mid-point off board (option 2), then the obvious thing to do would be to connect the mid-point to 0v, and the two end points to GPIO pins. This saves having to output anything to the drive lines before testing for a reset key press.

But as you say, what you are proposing is electrically equivalent to option 1, and will also work.

Bill.

[Dave]

Hi Bill,

it would not have been a problem, but I wanted the ability to disconnect the mod without having to do it at the back if the keyboard - hence the off board jumpers. I can make the DR7 off board connection to ground if you like? It sounds like it will make the software slightly simpler.

regards
Dave

[Bill B]

Dave,

Up to you. It is worthwhile supporting both options in the software anyway.

Bill.

[Crazyboss]

anyone tried PI Zero, as I understand its a very cheap PI ? but should be powerful enough.

[Bill B]

Claus,

I agree that the RPi Zero should be powerful enough to run MEMU, particularly with offloading the video scaling to the GPU.

I haven't actually tried MEMU on an RPi Zero (although I do have one). I have used it on an old RPi B+, which I think has the same processor, and that works fine.

Bill.