The secret to searching the net is using a couple of words and trying to think
of unique ones. E.g. in this case - hex bcd keypad. Note that "keypad" is a better
word than "keyboard" in this case. Also try to exclude words that you know will
trigger false hits.
I use
https://www.eniro.se to search and it performs well for me. It's a Swedish site
but you only need to know that "sök" means "search" in swedish. :wink:
Use quotes to search for sentences: "hex to bcd keypad"
And use the minus sign to exclude words: -software
As for the 1111 problem - one should never leave logic inputs floating to avoid
false values. You can either use a pull-up resistor to Vcc to set the input high,
or pull-down resistor to GND to set it low.
In this case four pull-down resistors to GND will give you a 0000 value. You can
use e.g. 10 kOhm for the resistors - it is not critical.
/Rambo