Phytec phyCORE-PXA255, Hardware Manual

Page: 75 / 106

Matrix Keyboard

PHYTEC Meßtechnik GmbH 2004 L-657e_0
67
16 Matrix Keyboard
The phyCORE-PXA255 is populated with a GPIO expander, which
can be used for the connection of a matrix keyboard. The signal lines
extend to connector X4 and are arranged in columns and rows. The
column outputs have an in-line resistance of 33R and the row inputs
have an RC combination with R=1 kOhm against VCC and
C = 100 nF against GND to prevent a possible signal bounce.
S S P
G P I O
E X P A N D E R
U 2
K E Y B O A R D
E G P I O 2 1 - 2 7
M A X 7 3 0 1
E G P I O 0 - 2 1
/ I N T ( E G P I O 2 7 )
F R A M
Figure 38: Matric Keyboard Connection