Gen 1.5 debug serial port (plus GPIO map)

Mitch Bradley wmb at
Fri Apr 17 16:11:48 EDT 2009

Are you sure we couldn't fit it in one of the existing openings for 
cables to come through?

    Big opening where the mic and backlight cables come out (looks like 
it would fit)

    Somewhat smaller one on the other side near the USB ports (probably 
big enough but might be hard to insert)

    Speaker cable openings (dodgy, but perhaps)

    LED openings near the bottom (dodgy, but perhaps)

I wonder if it's absolutely necessary to physically disconnect the 
camera when using the serial port?

If the connector is not populated, the effort of installing a serial 
port is increased to the point that people (at least me) will think 
thrice before doing it, thus making other solutions more attractive.

Perhaps there is some alternative to the existing connector that is 
easier to hook up to if not populated.  Holes or something.

If we assume the use of the USB version of the serial dongle, we don't 
need to supply power from the XO board, so only 3 pins are needed.

I'm just trying to think of ways to make it "less trouble than it's worth".

John Watlington wrote:
> On Apr 17, 2009, at 3:40 AM, Mitch Bradley wrote:
>> John Watlington wrote:
>>> In my day job (OLPC support), I'm constantly reminded of the importance
>>> of the serial port to repair centers.
>>> Here is the proposed plan of record:
>>> 1) There will be a prominently located (i.e. at the edge of the 
>>> board) jumper
>>>    which indicates to OFW that it should set up the VX855 to provide 
>>> a serial
>>>    port, and not a video capture port.
>>> 2) In order to use the serial port, a user should disconnect the camera
>>>    by removing the ribbon cable from the connector.
>>> 3) In production, both the jumper and the serial connector might be 
>>> depopulated.
>>>    In the process of soldering a serial connector on the board, the 
>>> jumper can be shorted...
>> I wonder if there is some location for the serial connector that 
>> would not require removing the back panel.   Perhaps somewhere near 
>> the backlight cable.  I'd like to eliminate the steps of removing the 
>> 4 screws underneath the display, removing the rocker so it doesn't 
>> fall out, carefully supporting the display while flipping the back 
>> unit to a position where you can release the back panel, then undoing 
>> that and replacing the 4 screws, then remembering to replace the rocker.
> Not without a tooling change, although it would be a
> minor one.  But so far we aren't planning any...
> I'm thinking about right above the rocker switch, where there
> is currently an opening allowing the speaker wire to be snaked
> through.
> Allowing access to the camera connector is a larger problem.
> Leaving the serial connector populated on production XOs was
> "an oversight", and the plan is to remove it this time. The cost is
> a few pennies, but they add up.
> Cheers,
> wad

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