[E3-hacking] DC adaptor?

[Cliff Lawson]

Don't know if this'll help y'all but in house we use little boxes with a bit
of veroboard on which sits a MAX232 (and some TTL inversion if being used
for E3). To power it we generally just use the 5V on USB and either stick
this into the E2/E3's own USB (except that they don't have the 5V enabled
until boot has finished) or (more usually) stick it into the USB on a nearby
PC. You don't even need a fancy USB plug to do this - the copper "fingers"
on a piece of veroboard are the same pitch as USB pins anyway so a "4 wide"
bit of veroboard stuffed into a USB is an easy way to get 5V to power a
MAX232. Alternatively you can power the boxes with a 5V "wall wart" or even
a bench PSU but, on the whole, the USB power route is the easy solution.

Cliff

> -----Original Message-----
> From: en4rab [mailto:en4rab at yahoo.com]
> Sent: 03 July 2005 04:51
> To: Discussion of the Amstrad E3 emailer hardware/software
> Subject: Re: [E3-hacking] DC adaptor?
> 
> 
> 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&c
> Path=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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