Multimedia Keyboard Transmitter
Designer Reference Manual DRM050 — Rev 0
28 Multimedia Keyboard Transmitter MOTOROLA
Figure 5-1. Keyboard Block Diagram
5.2.1 Microcontroller LK24
The functions of the LK24 are to scan the key matrix and determine what
keys are pressed and released, control the baseband IC to sending out
data, and perform the overall system control.
5.2.2 RF Transmission
The data from MCU will be transferred to the baseband IC for parallel to
serial packet conversion as well as error checking. The encoded data
will be passed to the RF module for ASK modulation in IF band and
frequency spreading with DSSS scheme. The modulated signal will be
further up-converted into the 2.4-GHz ISM band for final transmission.
2.4 GHz RF
Transceiver
Module
LOOP
ANTENNA
Baseband
MAC IC
D100
DC/DC Converter
3.3V
OSC1
OSC2
PTF0-7
PTC0-7
PTB6-7
PTA0-3
PTD4-7
[External
pullup R]
[External
pullup R]
(80-pin LQFP)
RST
ROW[0:7]
COL[0:17]
Key Matrix
(8 rows x 18 columns)
32.768kHz
10pF 10pF
X1
1uF
MC68HC908LK24
PTE7-PTE0
PTA7-PTA4
PTD3-PTD0
2M
DATA BUS
ADDRESS / CTL BUS
RFD_INT
IRQ
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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