#11887 LOW Not Tri: XO-1.75 Open Firmware reports continuous Keyboard interrupt if a GPS with PL2303 is attached

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#11887: XO-1.75 Open Firmware reports continuous Keyboard interrupt if a GPS with
PL2303 is attached
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           Reporter:  Quozl                |       Owner:  wmb at firmworks.com                
               Type:  defect               |      Status:  new                              
           Priority:  low                  |   Milestone:  Not Triaged                      
          Component:  ofw - open firmware  |     Version:  Development build as of this date
         Resolution:                       |    Keywords:                                   
        Next_action:  review               |    Verified:  0                                
Deployment_affected:                       |   Blockedby:                                   
           Blocking:                       |  
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Changes (by Quozl):

  * next_action:  diagnose => review


Comment:

 Summary: data sent by the GPS, such as the end of line marker (0x0d or
 0x0a), if sent at a low baud rate that is not 115200 baud, will be
 received as a NUL (0x00) or BREAK, and generate the ''Keyboard
 interrupt''.

 Tested with an XO-1.75 Q4D14ja, a USB serial adapter based on PL2303, a
 serial DE9 female to DE9 female crossover "null modem" cable, to another
 computer.

 With the other computer configured for 115200 baud, using ''screen
 /dev/ttyS0 115200'', the screen instance becomes a keyboard for the
 XO-1.75, and Ctrl/Space is treated by Open Firmware as a ''Keyboard
 interrupt''.

 With the other computer reconfigured for 1200 baud, pressing enter is
 treated as a ''Keyboard interrupt''.

 Open Firmware initialises the USB serial adapter to 115200 baud.  This is
 hard coded, but can be changed before inserting the adapter, like this:
 {{{
 \ boot
 \ insert adapter
 probe-usb
 dev /usb/serial
 patch 2580 1c200 pl2303-set-baud
 ?usb-keyboard
 }}}

 I suggest that in an application where a USB serial adapter is permanently
 connected with a device that is not generating data at 115200 baud, that a
 custom build of Open Firmware be prepared with a suitable change to pl2303
 -set-baud.  The olpc-firmware git repository has the procedures for
 building.

 We might also restore the behaviour to XO-1 and XO-1.5, as mentioned in
 #11871.

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Ticket URL: <http://dev.laptop.org/ticket/11887#comment:1>
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