Openmoko Bug #1682: Neo turns off before reaching X

[Openmoko Public Trac]

#1682: Neo turns off before reaching X
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 Reporter:  queen6           |        Owner:  openmoko-kernel
     Type:  defect           |       Status:  new            
 Priority:  high             |    Milestone:  ASU            
Component:  System Software  |      Version:  GTA02v5        
 Severity:  normal           |   Resolution:                 
 Keywords:                   |     Blocking:                 
Blockedby:                   |  
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Comment(by werner):

 This may be the VB_SYS bypass capacitor: GTA02v5 has a very small
 capacitor to
 stabilize the system voltage. It's perfectly conceivable that a different
 pattern of load changes could cause VB_SYS to break down before the USB
 host
 adjusts its output.

 If you like to play with a soldering iron, you could try to modify a USB
 cable
 and put a big capacitor (I'd try about 100uF) between GND and VBUS. The
 whole
 setup won't be USB-compliant (USB 2.0 section 7.2.4.1, page 177, only
 allows
 10uF, and we already exceed that by a considerable margin), but you can
 usually
 get away with that.

 You may also be able to get better results with a shorter or better
 quality
 USB cable, since it may reduce the voltage drop from host to device. Also
 a
 different host may perform better or worse.

-- 
Ticket URL: <https://docs.openmoko.org/trac/ticket/1682#comment:6>
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