Keyboard replacement
Posted: 08 Feb 2018 11:47
How often these days do we hear of MTXs with keyboard problems, repeating keys, "sticky" keys, plain dead keys ?
From the inventive mind of Bill Brending, here's the solution.
Use a PS2 keyboard instead!
Bill's idea is to use a Propeller to provide an interface between the serial PS2 protocol and the matrix based MTX keyboard header.
I've build a prototype to test the idea on a real MTX The 40 pin socket is for the propeller, with the usual 8 pin serial eeprom holding the boot code and a 3v LDO regulator to power both. The 2, 14 pin, sockets are for a pair of 7407 or 7417 open collector drivers to convert the 3v propeller output to 5v and cope with the resistors connected to the keyboard header in the MTX.
The reset button is now redundant, as a later revision of Bill's code allows reset from the keyboard just like the MTX.
In place, on a real MTX, with a keyboard attached. The flying lead to the central I/O socket is the 5v power source, as that's the only thing needed that's not available on the 20 way keyboard header. Having proved it works, Dave's been working on a layout that will fit under the keyboard to allow the case to be closed. The position of the propeller on the prototype prevents that.
On Dave's wish list, and there are hints that Bill may be able to get it to work, is adding USB keyboard support.
From the inventive mind of Bill Brending, here's the solution.
Use a PS2 keyboard instead!
Bill's idea is to use a Propeller to provide an interface between the serial PS2 protocol and the matrix based MTX keyboard header.
I've build a prototype to test the idea on a real MTX The 40 pin socket is for the propeller, with the usual 8 pin serial eeprom holding the boot code and a 3v LDO regulator to power both. The 2, 14 pin, sockets are for a pair of 7407 or 7417 open collector drivers to convert the 3v propeller output to 5v and cope with the resistors connected to the keyboard header in the MTX.
The reset button is now redundant, as a later revision of Bill's code allows reset from the keyboard just like the MTX.
In place, on a real MTX, with a keyboard attached. The flying lead to the central I/O socket is the 5v power source, as that's the only thing needed that's not available on the 20 way keyboard header. Having proved it works, Dave's been working on a layout that will fit under the keyboard to allow the case to be closed. The position of the propeller on the prototype prevents that.
On Dave's wish list, and there are hints that Bill may be able to get it to work, is adding USB keyboard support.