gnupic: 555 code dumper testing (was DIY USB programmer?)
Subject:
Re: 555 code dumper testing (was DIY USB programmer?)
From:
Byron A Jeff ####@####.####
Date:
21 Jan 2005 12:15:19 +0000
Message-Id: <20050121121515.GA22457@cleon.cc.gatech.edu>
On Fri, Jan 21, 2005 at 09:19:47AM +0000, Laurence Withers wrote:
> On Friday 21 January 2005 00:15, Byron A Jeff wrote:
> > I finally have a schematic for folks to examine and comment upon:
> >
> > http://www.finitesite.com/d3jsys/tbs555
> >
> > Any comments welcome. Be aware that the RX circuit in the top right
> > corner hasn't been wired or tested.
> >
> > Also there's no software yet. Alain and I are working together to see
> > if we can get a pkp that will drive it.
> >
> > Note that I didn't address the Vpp/Vcc issue. It's something that
> > will need some further discussion.
>
> Hi Byron,
>
> Wouldn't it be sensible to use a MAX-232? (note I didn't follow this
> discussion in great detail, so sorry if I missed some reasoning against
> it). Not only does it take care of the RS232 level conversion, you
> could also use the +12V charge pump which might well supply enough
> current for HVP.
>
> In terms of pricing/availability, at least in the UK, Rapid Electronics
> (http://www.rapidelectronics.co.uk/) sell the MAX-232 for UKP1.35; they
> also accept credit card orders with no minimum charge so that's quite
> useful for the hobbyists among us.
A MAX232 design certainly could be useful. The design is based on being able
to obtain readily available local components. I use what I call the Radio
Shack test: If I can find the component in my local Radio Shack here in
Atlanta, then it passes the test.
The reasoning is by using junkbox components, it'll be possible to put
together the programmer immediately instead of having to order and wait
for yet more components.
Also David was planning on repurposing a 555 in the intelligent USB part
of the design as a charge pump.
As designed the resistor/zener/transistor combo in the TX conditioning
circuit is reliable for RS-232 voltages.
BAJ
