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84 CY4672 Reference Design Guide, Document # 001-16968 Revision **
Bridge
duration elapses with no change in report data (see the HID Specification for more information on
this topic).
The check_usb_idle() function also checks the timeout for down key and ‘keep alive’ packet. A ‘keep
alive’ packet is transmitted every 65 ms during the time a key is pressed, so that the bridge can
detect if the RF link is lost, and in that unlikely case, the bridge inserts a ‘key up’ event, to prevent a
‘stuck key’ state being transmitted to the PC. The number of milliseconds before upkey reports are
generated is defined by DOWNKEY_TIME_OUT.
5.3.5.1.2 Check the Received Packet
When the bridge receives a valid packet, it parses this packet. If it is a data packet, the bridge for-
mats and sends a USB packet to the USB host. If it is a connect request with an approved device or
a ping request, the bridge sends a response correspondingly.
5.3.5.1.3 Check the Bind Button
The bridge checks the Bind button frequently. If this button is pressed, the bridge goes into the bind
state.
5.3.5.1.4 Check the USB Suspend
The check_usb_suspend() monitors the USB suspend condition on the USB bus and takes proper
actions to put the system into a low power state when no bus activity is observed for 3 ms.
When suspended, the bridge supports remote wakeup by intermittently turning the radio on when the
sleep timer interrupt occurs, checking for valid data from the HID devices, and then turning the radio
off again if no HID traffic was detected.
5.3.5.2 USB Module
This module parses the radio packets, builds the appropriate keyboard and mouse USB packets and
loads these packets into the endpoints.
5.3.5.3 Mfgtest Module
The manufacturing test module may be conditionally compiled in to provide manufacturing test sup-
port. The module configures the radio for reception and then enters a loop waiting for command
packets to be sent from the tester. The test echoes all echo command packets appended with the
number of invalid bits received and all other ‘valid’ command packets (no invalid bits). The manufac-
turing test code can only be exited by cycling power. The manufacturing test code in this bridge is
compatible with the CY3631 Manufacturing Test Kit offered by Cypress Semiconductor.
The manufacturing test mode on the PRoC LP RDK bridge can be entered by three different meth-
ods depending on the compile-time configuration.
Method 1: Press the Bind button during dongle insertion into the USB Host to enter the manufactur-
ing test mode.
Method 2: Force an SE1 condition (D+ and D – are both high) on the USB bus and at the same time
apply power to the bridge.
Method 3: Ground the P0.7 pin during dongle insertion into the USB Host to enter the manufacturing
test mode.
5.3.5.4 Encrypt Module
This module may be conditionally compiled in to provide encryption/decryption support. Encrypted
data transfers are typically used between RDK keyboard devices and the RDK bridge. Contact
Cypress Applications support for the encryption source code.
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