Normally,we need to connect 8 pins of 4x4 keypad to micro,occupying 8 pins on micro such as Arduino. But when we use the onewirekeypad technique, we need only one ADC pin. This adapter reduces the hassle to connect the divider resistors and keypad on breadboard,instead it plugs right into the keypad and can directly wired to the micro.
I built the circuit on a prefboard. Works nicely. Keys in bottom row don't work. All print 'D' when pressed. Need to see what's wrong.
Still using old resistor values. Ill change resistors when order reaches me. Photos of build posted. Other side of board will be posted when it arrives on my OneDrive.
I used the 4700 and 1000 Ohm resistor layout the author shows, and only keys 1-7 work correctly.. 8,9 are shifted to 7,8 and 0,# are shifted to *,0, so different values must be required. Or its very sensitive to supply voltage? or keypad resistance.. not sure. Welcome to Analog troubleshooting! :) Let me know if you found a solution, I'll post mine (if I find one).
Update - in increased the voltage on my 5v bus to 4.96 from 4.5, (which matches the 5v output from my nano) and it works better. only 0,# are unstable now. I suppose altering the entire set of resistors (shift them down perhaps? to counteract keypad resistance) or just all the column resistors? Or perhaps this helps - looks like the author is responding here: https://brainy-bits.com/forums/topic/onewire-keypad/
Update - with USB and external power connected, the keypad works.. unplug the USB from my nano and it doesent read the last 2 keys.. i havent given up yet. :) I need those extra pins!
Tnx a lot. All works fine!!!
4k7 + 1k
library: https://github.com/AndrewMascolo/OnewireKeypad