Forums

Building DIY wiggler w/74VHC08

Started by Ed Schlunder January 16, 2006
I'm thinking of building the DIY wiggler so that I can program and
debug some LPC2103 chips on the cheap.

I see the wiggler.txt schematic in the files area. It is using a
74AC244 chip to do voltage level conversion between the PC and the
LPC21xx chip. It only seems to use 4 line drivers of the 74AC244 chip
(half the chip is left unused).

Would there be any problem with using a 74VHC08 quad 2 input AND gate
chip instead? I would just tie one side of each AND gate high so that
it can be used as 4 line drivers. This chip is cheaper and smaller
than the 74AC244.

The schematic also uses a DTC114 NPN transistor. I don't have any
DTC114 transistors. Would MMBT3904 work okay instead?

Any other tips for a DIY wiggler?


An Engineer's Guide to the LPC2100 Series

--- In lpc2000@lpc2..., "Ed Schlunder" <zilym@y...> wrote:
>
> I'm thinking of building the DIY wiggler so that I can program and
> debug some LPC2103 chips on the cheap.
>
> I see the wiggler.txt schematic in the files area. It is using a
> 74AC244 chip to do voltage level conversion between the PC and the
> LPC21xx chip. It only seems to use 4 line drivers of the 74AC244
chip
> (half the chip is left unused).
>
> Would there be any problem with using a 74VHC08 quad 2 input AND
gate
> chip instead? I would just tie one side of each AND gate high so
that
> it can be used as 4 line drivers. This chip is cheaper and smaller
> than the 74AC244.
>
> The schematic also uses a DTC114 NPN transistor. I don't have any
> DTC114 transistors. Would MMBT3904 work okay instead?
>
> Any other tips for a DIY wiggler?
>

Unless actually building/debugger a wiggler is your gig, you might
consider purchasing a cheap clone e.g. http://olimex.com/dev/arm-
jtag.html


----- Original Message -----
From: "Ed Schlunder" <zilym@zily...>
To: <lpc2000@lpc2...>
Sent: Monday, January 16, 2006 7:09 PM
Subject: [lpc2000] Building DIY wiggler w/74VHC08 > I'm thinking of building the DIY wiggler so that I can program and
> debug some LPC2103 chips on the cheap.
>
> I see the wiggler.txt schematic in the files area. It is using a
> 74AC244 chip to do voltage level conversion between the PC and the
> LPC21xx chip. It only seems to use 4 line drivers of the 74AC244 chip
> (half the chip is left unused).
>
> Would there be any problem with using a 74VHC08 quad 2 input AND gate
> chip instead? I would just tie one side of each AND gate high so that
> it can be used as 4 line drivers. This chip is cheaper and smaller
> than the 74AC244.
>
> The schematic also uses a DTC114 NPN transistor. I don't have any
> DTC114 transistors. Would MMBT3904 work okay instead?
>
> Any other tips for a DIY wiggler?

My version in jtag.zip definitely works!

What you propose should be OK. Don't forget to link pins 8 and 15 on the
DB25 connector if you are using the Macraigor software.

Leon


Leon:

Do you find any instability with your JTAG debugger? I'm very confused as
to why this would be instable, and if it is, why hasn't anyone figured out
why and fixed it? Considering the cheapest alternatives are several
hundred dollars more expensive, I'm confused why we don't have a rock solid
wiggler compatible JTAG debugger developed.

-- Sean

At 02:31 PM 1/16/2006, you wrote:
>----- Original Message -----
>From: "Ed Schlunder" <zilym@zily...>
>To: <lpc2000@lpc2...>
>Sent: Monday, January 16, 2006 7:09 PM
>Subject: [lpc2000] Building DIY wiggler w/74VHC08 > > I'm thinking of building the DIY wiggler so that I can program and
> > debug some LPC2103 chips on the cheap.
> >
> > I see the wiggler.txt schematic in the files area. It is using a
> > 74AC244 chip to do voltage level conversion between the PC and the
> > LPC21xx chip. It only seems to use 4 line drivers of the 74AC244 chip
> > (half the chip is left unused).
> >
> > Would there be any problem with using a 74VHC08 quad 2 input AND gate
> > chip instead? I would just tie one side of each AND gate high so that
> > it can be used as 4 line drivers. This chip is cheaper and smaller
> > than the 74AC244.
> >
> > The schematic also uses a DTC114 NPN transistor. I don't have any
> > DTC114 transistors. Would MMBT3904 work okay instead?
> >
> > Any other tips for a DIY wiggler?
>
>My version in jtag.zip definitely works!
>
>What you propose should be OK. Don't forget to link pins 8 and 15 on the
>DB25 connector if you are using the Macraigor software.
>
>Leon




--- In lpc2000@lpc2..., Sean <embeddedrelated@w...> wrote:
>
> Leon:
>
> Do you find any instability with your JTAG debugger? I'm very
confused as
> to why this would be instable, and if it is, why hasn't anyone
figured out
> why and fixed it? Considering the cheapest alternatives are several
> hundred dollars more expensive, I'm confused why we don't have a
rock solid
> wiggler compatible JTAG debugger developed.
>
> -- Sean
>

History has shown that when people build their own, problems acure.
When those same people buy a working wiggler, problems are solved.

Please, build your own. But if you start have problems, buy a
pre-built one and check your work.

I had built 2 wigglers from scratch. Bought one, then built a third.
Only the last two worked.

I think the problem is the design is _too_ simple. So it looks like it
should always work.

Good Luck

Let us know if yours works.

hamilton


----- Original Message -----
From: "Sean" <embeddedrelated@embe...>
To: <lpc2000@lpc2...>
Sent: Monday, January 16, 2006 7:44 PM
Subject: Re: [lpc2000] Building DIY wiggler w/74VHC08 > Leon:
>
> Do you find any instability with your JTAG debugger? I'm very confused as
> to why this would be instable, and if it is, why hasn't anyone figured out
> why and fixed it? Considering the cheapest alternatives are several
> hundred dollars more expensive, I'm confused why we don't have a rock
> solid
> wiggler compatible JTAG debugger developed.

Mine works very well, better than the real Wiggler I've got.

Leon


Hamilton:

What did you do differently between the two that you built?

-- Sean At 03:15 PM 1/16/2006, you wrote:
>--- In lpc2000@lpc2..., Sean <embeddedrelated@w...> wrote:
> >
> > Leon:
> >
> > Do you find any instability with your JTAG debugger? I'm very
>confused as
> > to why this would be instable, and if it is, why hasn't anyone
>figured out
> > why and fixed it? Considering the cheapest alternatives are several
> > hundred dollars more expensive, I'm confused why we don't have a
>rock solid
> > wiggler compatible JTAG debugger developed.
> >
> > -- Sean
> >
>
>History has shown that when people build their own, problems acure.
>When those same people buy a working wiggler, problems are solved.
>
>Please, build your own. But if you start have problems, buy a
>pre-built one and check your work.
>
>I had built 2 wigglers from scratch. Bought one, then built a third.
>Only the last two worked.
>
>I think the problem is the design is _too_ simple. So it looks like it
>should always work.
>
>Good Luck
>
>Let us know if yours works.
>
>hamilton >
>
>----------
>>Yahoo! Terms of Service. >----------




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Hash: SHA1

Ed Schlunder wrote:
> I'm thinking of building the DIY wiggler so that I can program and
> debug some LPC2103 chips on the cheap.
>
> I see the wiggler.txt schematic in the files area. It is using a
> 74AC244 chip to do voltage level conversion between the PC and the
> LPC21xx chip. It only seems to use 4 line drivers of the 74AC244 chip
> (half the chip is left unused).
>
> Would there be any problem with using a 74VHC08 quad 2 input AND gate
> chip instead? I would just tie one side of each AND gate high so that
> it can be used as 4 line drivers. This chip is cheaper and smaller
> than the 74AC244.
>
> The schematic also uses a DTC114 NPN transistor. I don't have any
> DTC114 transistors. Would MMBT3904 work okay instead?
>
> Any other tips for a DIY wiggler?

I just bought an Olimex Wiggler clone, it cost about 24 euros.
It can't make it work very well with OCDRemote (only at the
lowest speed), but it works without any problems with OpenOCD.

Perhaps we can improve upon the existing designs and create
the ultimate low-cost ARM JTAG cable, yet keeping it simple.
Some ideas:
* provide proper current limiting for all lines
* add readback of the RTCK signal (return clock)
* add readback of the targets' VCC (like the Olimex clone does)

Regards,
Bertrik
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--- In lpc2000@lpc2..., Sean <embeddedrelated@w...> wrote:
>
> Hamilton:
>
> What did you do differently between the two that you built?
>
> -- Sean
This first one I built was from parts in my junk box.
A scrap vector board and a db-25 connector.

Through it together one late night.
Looked like hell, but its such a simple circuit.

Never worked.

Second one, I built with a little more care.
Some new parts, some scrap parts.

It looked like it worked, and the slowest speed. But it was flakey.
Failed more then it worked. ( Atmel demo board)
So I bought one from sparkfun.com

That one worked fine. So I built another just to see if I lost
my knack in building things.

The last one seemed to work OK, but still flakey.
I just gave up and use the pre-built one.

I have been building things for 20 years. This is not new.
Whenever I see someone posting a message that they can not get
a wiggler working, I have to ask "did you build it yourself ?".
Most times its yes, "but its such a simple circuit !!"

go figure.

hamilton


Ed Schlunder wrote:

>I'm thinking of building the DIY wiggler so that I can program and
>debug some LPC2103 chips on the cheap.
>
>I see the wiggler.txt schematic in the files area. It is using a
>74AC244 chip to do voltage level conversion between the PC and the
>LPC21xx chip. It only seems to use 4 line drivers of the 74AC244 chip
>(half the chip is left unused).
>
>Would there be any problem with using a 74VHC08 quad 2 input AND gate
>chip instead? I would just tie one side of each AND gate high so that
>it can be used as 4 line drivers. This chip is cheaper and smaller
>than the 74AC244. >
However, it may not have the same drive levels (output current). The
'244 series is a buffer / driver, typically producting 12ma sink and 4ma
source. The '08 is a logic device, not a driver, you will probably
only find that it can do +/- 4ma (if you are lucky).

Output impedance would dictate how quickly signals may be driven high /
low on the JTAG interface. Too high an impedance == lousy signal edges
/ ring / overshoot.

TomW --
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
----------------