Lpc2000

I've just traced through the circuit of the Wiggler, simplified it (I
didn't see why it needed two buffers in series on most of the signals)
and put it into my PCB package as a schematic. I've uploaded it as a
PDF file, if anyone cares to check it. I've deleted my previous JTAG
interface file, as it isn't compatible with any of the software that
works with the Wiggler (signals were on different DB-25 pins).

Leon

--- In lpc2100@yahoogroups.com, "leon_heller" <leon_heller@h...> wrote:
> I've just traced through the circuit of the Wiggler, simplified it (I
> didn't see why it needed two buffers in series on most of the signals)
> and put it into my PCB package as a schematic. I've uploaded it as a
> PDF file, if anyone cares to check it. I've deleted my previous JTAG
> interface file, as it isn't compatible with any of the software that
> works with the Wiggler (signals were on different DB-25 pins).

I was wrong about my original interface, I'd got the DB25 connected up
incorrectly - I'd designed the PCB for a female instead of a male
connector. Cutting a few tracks and rewiring my home-made prototype
PCB correctly got it working.

It seems to work OK without a connection to nTRST. nTRST on the target
board should be tied high through a 10k resistor and connected to pin
3 of the JTAG connector if you want compatibility with the Wiggler.

I'll upload the corrected files in a day or so when I've made a new
PCB and checked that it works.

Leon

On Sun, Feb 01, 2004 at 06:15:29PM -0000, leon_heller wrote:
> I've just traced through the circuit of the Wiggler, simplified it (I
> didn't see why it needed two buffers in series on most of the signals)
> and put it into my PCB package as a schematic. I've uploaded it as a
> PDF file, if anyone cares to check it.

Don't you have to put the resistors between the parallel port and the
buffer? The buffer gets its power from the target board which is 3.3V.
As far as I know PC parallel ports are still running at 5V, at least
older ones. The AC244 does have the usual input protection diodes, so
I think you need current limiting resistors between PC and buffer.

Or is there some kind of magic going on which I don't understand?

Soeren

>From: Soeren Gust <gust@...>
>Reply-To: lpc2100@yahoogroups.com
>To: lpc2100@yahoogroups.com
>Subject: Re: [lpc2100] JTAG interface
>Date: Mon, 2 Feb 2004 14:57:53 +0100
>
>On Sun, Feb 01, 2004 at 06:15:29PM -0000, leon_heller wrote:
> > I've just traced through the circuit of the Wiggler, simplified it (I
> > didn't see why it needed two buffers in series on most of the signals)
> > and put it into my PCB package as a schematic. I've uploaded it as a
> > PDF file, if anyone cares to check it.
>
>Don't you have to put the resistors between the parallel port and the
>buffer? The buffer gets its power from the target board which is 3.3V.
>As far as I know PC parallel ports are still running at 5V, at least
>older ones. The AC244 does have the usual input protection diodes, so
>I think you need current limiting resistors between PC and buffer.
>
>Or is there some kind of magic going on which I don't understand?


Yes, it probably would be a good idea. The Wiggler doesn't have them, 
though. I'm actually using an HC244 - it works OK. The  parallel port I'm 
using has resistors in series with the outputs, anyway. I think the 
resistors on the JTAG outputs are to stop ringing on the lines.

Leon
--
Leon Heller, G1HSM Tel: +44 1424 423947
Email: aqzf13 at dsl dot pipex dot com
WWW: http://www.geocities.com/leon_heller

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I've just uploaded a file (jtag.zip) to the Files area with pics of my
home-made JTAG interface. It works fine with my LPC210x boards and the Atmel
EB01 ARM board.

The single-sided PCB may easily be made with rudimentary PCB facilities.

I'll be adding the artwork, schematic etc.

Leon
--
Leon Heller, G1HSM
Email: aqzf13@...
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html

I've now included the schematic, PCB layout and artwork laser printer
.prn file for my JTAG interface in file jtag.zip. Just copy jtag.prn
to the laser printer to produce a transparency for making the PCB.
Tracing paper works very well. Red tracks are wire links on top of the
board.

I used a 74HC244 instead of a 74AC244, as I've got lots of them. With
a short cable length like I'm using (about 12 cm) it doesn't really
matter.

Leon