SOLUTIONS CUBED MEMKey Quick Start Manual

Electronics Prototyping, Custom Design, Product Development
MEMKey
Keypad Encoder
*4X5 Matrix
*Programmable Rows & Columns
*PC/AT or Serial Output
AN-303 A Simple Calculator Using a Basic Stamp II
This application demonstrates the use of a MEMKey in a 7 digit decimal
calculator consisting of a 2x8 LCD screen and a Grayhill 4x4 keypad. The LCD,
operating in 4-bit mode, is driven by a Basic Stamp II while a MEMKey serial
keypad encoder interfaces to the keypad.
The calculator performs binary addition and subtraction. Subtraction is
accomplished by taking the 9's complement of one operand and adding it to
another. The keypad, a Grayhill 96 series, has four function keys. "A" (location
3) is the addition key, "B" (location 7) is the subtraction key, "C" (location 11) is
the equals key, while "D" (location 15) serves as a reset button.
When overflow occurs (result is greater than 7 digits), "OVERFLOW" appears at
the top of the screen and the calculator waits for a reset signal.
The MEMKey's row and column configuration defaults to the low cost Grayhill 96
series keypads, which are available from both Parallax and Digi-Key. The 2x8
LCD screen (Optrex DMC-50448N) that this application uses is also available
from Digi-Key. A hardware schematic follows:
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