Intermec 073289-001 User Manual

Since KEY_RET0 can toggle PXA255 GPIO1, which is always enabled as 
a system wakeup pin, any key located in keypad Row 0 functions as a 
wakeup key if its column line is driven low during Suspend. 

In the first three keypad styles, the 1, 2, 3, Scan button (where present), 
and handle trigger keys are all placed in Row 0 as potential wakeup keys. 
In future OS releases, these may be user-configured to wake the system 
from Suspend. Current software, though, has no support for this feature. 
All eight-column lines are also set to Hi-Z on Suspend. 

Note that a vulnerability may arise in future releases if the handle trigger is 
enabled as a wakeup “key”: Since the handle trigger is a magnetic reed 
switch that is sensitive to mechanical shock, abruptly snapping a main 
battery in place after a battery swap can unexpectedly wake the system by 
causing the reed switch to bounce. 

The I key (signal IO_KEY*) is a simple contact closure to GND. It is not 
part of the scanned keypad matrix. This signal is debounced in the PSC 
(U38) for between 50 ms and 100 ms. The long debounce period is 
necessary to prevent unwanted suspends in drop. 

The keypad Scan Button (where present) and Handle Trigger are handled 
as scanned keys in the keypad matrix (as opposed to using discrete IO). 
They are placed in Row 0 of the keypad matrix for future “trigger-resume” 
support (See “Wakeup Keys” on page 68). Each returns a unique scan code 
so that they can be used for different scanning functions. 

Multiple keypad formats and overlays are supported. The installed keypad 
is identified through the hardware configuration table stored in non-
volatile memory (flash). The keypad itself has no provision to allow 
software to read a unique keypad ID. 

A Mini PCI bridge is implemented in the FPGA as a high-bandwidth 
interface to support Ethernet and 802.11g cards. The bridge is based on 
“LogiCore” PCI interface IP from Xilinx, and on PCI bridge IP from 
NMI, Ltd.