i want to use the calculator keypad as an input


Thread Starter

Eng.aladdin eid

the problem is i can't find any datasheet for the calculator and with 29 bit line to the lcd its impossible to know how it works

can any one help me...????

Curt Wuollet

Best way I've found is to get one of the Matrix Orbital displays with a keypad encoder and a keypad and communicate through its serial port. Most calculators would have two places you can access, the keypad crosspoint matrix and the LCD terminals. Niether provides a signal easily convertible to something usable. The keypad is the
best bet, but you need to monitor the scan and a coincidence signal. The LCD stuff is non standard voltages and really busy to deal with. It's quite a bit easier to use the Matrix Orbital as it has the keypad encoder and a serial port with the electronics to do the conversion. I succesfully used these for an input terminal and they were built into a time and attendance system at our plant as well. Bear in mind that this is advice from the ultimate do it yourselfer and I know how to do it both ways.