[E3-hacking] DC adaptor?

[en4rab]

Im afraid I dont know anywhere that sells a finished product in a nice
box but I have a couple of ideas.
The first idea which im fairly sure will work ok is to buy a max232
interface from either here:
http://www.tailor-madecircuits.com/rs232_max.htm
or here:
http://shop.jabsplace.co.uk/index.php?main_page=product_info&cPath=11&products_id=8

These are meant to draw their power from the target device so they have
a pin for 5v to be applied to, since the E2 doesnt have an easily
accessable supply, unless you dragged the jtag port out to a connector
on the back :), It would probably be possible to power the interface
with a 4.5v cmos backup battery such as this one from maplin:
http://www.maplin.co.uk/Module.aspx?ModuleNo=22787&doy=3m7D
connect the battery accross vcc and gnd, and then make a lead to take
rxd txd and gnd to the exp port.
Just be sure to disconnect the battery when the interface isnt in use.
This is just an idea off the top of my head and it hasnt been tested,
the only issue i can think of is if 4.5v is enough for the max 232 which
is a 5v part i think.

Im still not 100% sure what voltage the exp port is supposed to work at,
from reading other arm documentation i was under the impression that arm
devices I/O was 3.3v or there abouts so when i built my interface I used
a max3232 which is designed for operation from about 3v to 5v and i took
my supply from the the same point I used for Vref for the jtag, but
others on this list are using 5v so i guess that is ok.
(I must read the docs sometime lol)

A slightly more off the wall idea might be to sacrifice a datacable for
a nokia phone, i *think* that would work, and as a bonus should draw its
power from the PC's serial port, but i would have to look into it some
more.
The 2 shops above are selling the max232 interfaces because they are
being used by people to communicate with a pace set top box, but others
have used nokia data cables with the ends chopped off to achieve the
same results.
Im off work on monday if i get a chance i wiil have a root about and see
if i can find a data cable to try it.
If you wanted to have a go, try to find the oldest nokia cable you can
and preferably an fbus only type (or one you can switch between f and m
bus)
The F bus type has txd rxd and gnd (mbus has rxd and txd as one wire i
think) I think a 3210 cable should work ok but other types should too.

This is all untested though so dont hold me responsible if your E2 blows
up or it doesnt work.
your mileage will vary.
en4rab

--- David Given <dg at cowlark.com> wrote:

> Now I've discovered that my TTL line level converter board seems to
> have died. 
> Given that I had endless grief getting this to work in the first
> place, does 
> anyone know where I can get a ready-made converter that comes in,
> like, a 
> box? I know that the radio HAM community uses these things a lot, so
> they 
> might be a good source --- any suggestions?
> 
> -- 
> "Curses! Foiled by the chilled dairy treats of righteousness!" ---
> Earthworm 
> Jim (evil)
> > _______________________________________________
> e3-hacking mailing list
> e3-hacking at earth.li
> http://www.earth.li/cgi-bin/mailman/listinfo/e3-hacking
> 


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