#9776 HIGH Not Tri: XO-1.5 B3 only boots when serial port connected

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#9776: XO-1.5 B3 only boots when serial port connected
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 Reporter:  wad                  |                 Owner:  wmb at firmworks.com
     Type:  defect               |                Status:  new              
 Priority:  high                 |             Milestone:  Not Triaged      
Component:  ofw - open firmware  |               Version:  1.5-B3           
 Keywords:                       |           Next_action:  reproduce        
 Verified:  0                    |   Deployment_affected:                   
Blockedby:                       |              Blocking:                   
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 I have one XO-1.5 B3 prototype (with Q3A16 and OS44 installed) which
 refuses to boot unless there is a serial port connected to the CPU serial
 port.

 This is independent of whether or not a camera is connected, or the
 SERIAL_EN jumper is set or clear (I verified with ohmmeter that the jumper
 is really being cleared.)

 I verified the value of R247 (the damping line on incoming data) and also
 tried reducing it to 4.7K with no effect.

 The EC port shows that with no serial port connected, we get few POST
 codes from OFW.  With a serial port connected, the POST code series is:
  1D  22  2F  40  45  47  48  4C  4D  4E  4F  50  52

 With no serial port connected to the CPU port, no POST codes are reported
 by the EC.

 The connected serial port must be powered on to have a positive effect.

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Ticket URL: <http://dev.laptop.org/ticket/9776>
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