Velesoft,
Nice idea, I was thinking of reusing a PC standard keyboard membrane, but it is hard to find one with a layout similar to this of ZX. There are 3 things that bother me when I look at your project:
- How are you going to use a membrane with a different cols/rows layout, keeping a 100% compatibility to the ZX keyboard?
This membrane is absolutly different than ZX membrane and need own decoder (CPLD). CPLD will convert this toshiba matrix to ZX/SAM COUPE membrane matrix. But in my clone will used sram memory with conversion table. Thanks to sram can be table rewrited and we can connect any other laptop keyboards with different membrane. Clone can contain in main rom BIOS page with small routine for keyboard calibration (you must press separately each key and routine automatically detect position in new membrane and after press all keys can be saved new conversion table to eeprom/flash eprom memory. Theoretically will possible connect all existing laptop keyboards :-)
- How is it supposed to work with any ZX software if you use a 251 port? Custom ROM?
This schematic is only example of connection to ZX bus = for testing. Port can be changed to any other value but with this schematic can't be keyboard use as ZX keyboard replacement, because matrix and communication are different. ZX keyboard is readable direct via single IN command, but this toshiba membrane contain too much solumns and must be used different method of reading = before reading data must be writed column number to port 251.... If we rewrite keyboard routine in ZX rom, then will possible use this laptop keyboard in ZX basic or with some old ZX software using rom routines for reading keys.
- Are you going to adapt a SAM Coupe case for this? Meaning - you are about to destroy a good SAM keyboard in order to build yours?
This is only idea. I plan make own case, similar as on picture.
Or we can use original case for laptop Toshiba Satellite C660 because this keyboard size is designad specially for it (ZX clone in laptop case) :-)
More photos here:
http://oldcomp.cz/viewtopic.php?f=65&t=1097#p12877