Receiver Firmware
DRM055
36
Freescale Semiconductor, Inc.
For this short detection period, there is the possibility that the noise hit into the
RF front end would have a pattern like a packet portion. Therefore, if a packet
portion is detected, the MCU will turn on for a longer duty cycle. This duty cycle
is for receiving the next complete RF packet that can wake up the host.
The mechanism and the timing parameters for detecting a wakeup packet are
shown in
Figure
7-7,
Figure
TRANSMITTER
MOUSE PACKET
JB12 IRQ
JB12 WAKEUP
DUTY CYCLE
t
: Length of one complete RF packet
PKT
t
: Time interval of successive IRQ wakeup periods during device suspend.
IRQ
t
: Duration of MCU being turned on in each IRQ wakeup period. MCU is turned
ON1
on in this period to detect a (portion of) RF packet has been received.
Figure 7-7. Timing Parameters for Packet Detection
TRANSMITTER
RF PACKET
MOUSE PACKET
JB12 IRQ
JB12 WAKEUP
DUTY CYCLE
PORTION OF
PACKET DETECTED
If during a t
period a portion of a RF packet is detected, the RF receiver will turn on (t
ON1
for a longer time to detect a complete RF packet.
If one complete RF packet is received, the MCU will wake up the host.
Figure 7-8. Detection of Valid Wakeup Packets
Receiver Firmware
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7-8, and
Figure
7-9.
RF PACKET
t
PKT
t
IRQ
t
ON1
t
Sleep
RF PACKET
t
ON1
t
ON2
High Data Rate Wireless USB Optical Mouse Solution
NEXT MOUSE PACKET
VALID DATA DETECTED
JB12 WILL WAKE UP
THE HOST
)
ON2
MOTOROLA