Hi, I have one of these systems and need a replacement RKP, Long story short i purchased an ADE (Honeywell) G4 system for my daughters house she was buying back in 2020 but what with recent global events the sale fell through and only now has she got another house, the issue is she needs another keypad for upstairs and as you may know these are now impossible to buy so i will be making my own.
So far:
The accenta RKPs send out 3 bytes of data for any key press, the 1st byte is the letter K (ascii), the second byte is the key e.g. 1,2,3 etc as you already know, the 3rd byte is is a combination of both bytes of data (XOR) (guessing for error checking at the controller?) the byte is constructed of 1 start bit, 8 data bits, 1 parity bit and 2 stop bits. the tricky part is the parity bit that is both odd and even that arduino/AVR processors do not natively support nor has anyone written a software serial lib to support differing parity bits within the same message. As a hack i have got around this in hardware by sending the letter J and in hardware sending a single pulse for the first byte of data. This results in the "odd" parity bit required by the alarm but it still sees the letter K (J=01010010 where K is 11010010), doing it this way i can use the default HW serial port set to 1200 baud, 8E2 (8 data bits, even parity and 2 stop bits) and it just needs one diode to combine the 1st bit of data.
Just have to read the LCD and LED data now!
