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Configuration and Operation
M9328MX21ADSE User’s Manual, Rev. A
Freescale Semiconductor 2-9
2.3.8 CD Quality CODEC
The ADS has a Wolfson WM8731SEDS 32-bit linear low power stereo CODEC with a built-in headphone
driver (U24). The CODEC is controlled by the i.MX21, which sends the digital audio data via an SSI2
interface and control data via an I
2
C interface.
The CODEC has stereo line and mono microphone level audio inputs as well as stereo headphone outputs.
It features a mute function, programmable line level volume control, and a bias voltage output suitable for
an electret type microphone. Table 2-5 shows the CODEC connectors and describes their basic functions.
The WM8731SEDS data sheet is available at http://www.wolfsonmicro.com/
2.3.9 Keypad
The ADS includes an external keypad module that connects to the Base board. The keys provide tactile
feedback. The i.MX21 keypad interface reads the pad via the KCOL[5:0] and KROW[5:0] signals. the
interface has chording diodes to prevent ghost key presses. The keys are labeled with numeric, cursor
control, soft key, and spare key functions, but the actual functionality is determined by user software. The
default keypad can be replaced by a custom design. The UART2 signals that are multiplexed internally
with the KCOL[7,6] and KROW[7,6] signals are brought out to keypad connector P5. This allows the use
of an 8x8 keypad matrix. Table 2-6 shows the key switch connections to the keypad signals by function
name (as labeled on the PCB) and the switch reference designators.
Table 2-5. Audio Connectors
Connector Descriptions
P10 Stereo line in jack
P11 Dynamic microphone input jack
P12 Headphone jack for audio out
Table 2-6. Keypad Layout and Connections
KCOL5 KCOL4 KCOL3 KCOL2 KCOL1 KCOL0
KROW5
APP1
SW1
SEND
SW2
KEY 1
SW3
UP
SW4
KEY 2
SW5
END
SW6
KROW4
APP2
SW7
HOME
SW8
LEFT
SW9
ACTION
SW10
RIGHT
SW11
BACK
SW12
KROW3
DOWN
SW13
APP3
SW14
1 -
SW15
2 ABC
SW16
3 DEF
SW17
EXTRA 2
SW18
KROW2
VOL UP
SW19
APP4
SW20
4 GHI
SW21
5 JKL
SW22
6 MNO
SW23
EXTRA 3
SW24
KROW1
VOL DOWN
SW25
EXTRA 1
SW26
7 PQRS
SW27
8 TUV
SW28
9 WXYZ
SW29
EXTRA 4
SW30
KROW0
POWER
SW31
RECORD
SW32
*
SW33
0 +
SW34
#
SW35
EXTRA 5
SW36