[Repairs] [support-gang] Fwd: Serial adapter for repair centers cost question

John Gunkel jgunkel at gmail.com
Fri May 23 15:05:04 EDT 2008

On Fri, May 23, 2008 at 11:23 AM, Ian Daniher <it.daniher at gmail.com> wrote:
> If I can get the XO motherboard cord/connector, I can  build a limited
> number of TTL(5v) to serial and TTL->USB for less than five dollars each

You don't want to do that, as the XO-1 has J1 as a 3.3V port.
A different part would work, but it would need to drive it's outputs at 3.3V

> using MAX233 chips and usb-serial connectors from dealextreme.com. I'd have
> to test to verify that lvttl wold work with this device.  It would be very
> helpful stock repair centers with these cords. An alternative is getting

The $0.50 cables would be ideal. Stick two taped between some
cardstock in an envelope and send it out to all the repair centres.
Those with the appropriate USB or serial converter will be immediately
functional.For the rest, see below, or, a null modem cable (XO->XO)
could be made at "the big end" of the cables by connecting both pins 4
together, connecting one pin 2 to the other pin 3, and finally
connecting the other pin 2 to the first's pin 3.

> crossover cables (double female) allowing for two XOs to be used, rather
> than  an XO and a computer with USB.
> Cautionary words, likely already said: These cables can be used to brick,
> unbrick, and disable the security on XOs. If we're not prepared to deal with
> people who have borked their laptops with these devices, pulled off the
> jumpers on the motherboard, etc, I believe we need to have them available,
> but not just to the general public.
> My .02usd,
> Ian Daniher
> On Fri, May 23, 2008 at 10:37 AM, Steve Holton <sph0lt0n at gmail.com> wrote:
>> ---------- Forwarded message ----------
>> From: Steve Holton <sph0lt0n at gmail.com>
>> Date: Fri, May 23, 2008 at 10:37 AM
>> Subject: Re: [Repairs] Serial adapter for repair centers cost question
>> To: richard at laptop.org
>> On Fri, May 23, 2008 at 9:55 AM, Richard A. Smith <richard at laptop.org>
>> wrote:
>> > I'm going to submit 2 additions to the spare parts list for repair
>> > centers.
>> >
>> > 1 is the cable that you use for connections to the laptop serial port.
>> > Qty 500 I've got a quote for $.50.

Now, If you have a quote for a cable, but have not yet ordered them,
my suggestion would be to have the big end broken out as 3+1, that is,
a female three pin connector on the one end for GND, TX and RX, then a
single for the 3.3V signal. This makes the whole thing significantly
more oops proof

>> These are the 4 slot connector for J1, right?
>> >
>> > The 2nd is the custom usb to serial adapter which in its current form
>> > will cost about $35 bucks or so.  Perhaps less if we buy them in larger
>> > quantities.
>> Are these essentially the same as this:
>>  http://www.ftdichip.com/Products/EvaluationKits/TTL-232R-3V3.htm
>> but with a 4 pin connector?

I can answer this with a definite yes. In fact, if you were to take
one of these cables, and a three post male-to-male header, you have a
complete de-bricking kit. Coincidentally, this is how I built cable
the cable I use.

>> > My question is that is $35 (plus markup) going to be ok for grassroots
>> > repair centers?  They may need several depending on the size.
>> Is the D6 bricking a one-off thing, or do we expect there to be more
>> cases where repair centers will need to access the XO through the
>> serial port?

Picture this, a repair centre gets in a suspected brick, and you don't
see anything on the screen. Is it a D6 brick, or did the "weekend
developer" trash their x config trying to get a USB adapter working?
(or any number of other possibilities) With a serial console, you can
see at what level that problem is.

As repair centres, we are going to be dealing with hardware. By having
access to a mechanisim that we can see with some certainty that "yes,
Linux has started" or even (sigh) "The windows recovery mode prompt
has shown up" Versus "Why does this stop at the ok prompt?" you can
quickly eliminate entire classes of problems. This will mean the
difference between a repair "I fixed your XO by reflashing build 703"
and a replacement "I couldn't tell what the problem was, so I swapped
the mainboard" which is probably a concern for many.

>> Has anyone seen an interest (from XO owners, or weekend developers) in
>> buying these cables for 'home' use?

I would actually expect that at least some of the weekend developers
are people that have such a USB-> 3.3V serial adapter for tweaking
their NSLU2s and WRTs  :)

Thus, the only thing these guys need is an adapter that will fit in J1

>> Is there any thougt about  repair centers selling a kit to build one
>> of these from discrete components and boards? This is beginning to
>> sound like franchising.

In fact, that was the exact thought I had, and why I asked for the
part number ;)


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