Announce: 1 Pin Interface - FPGA and HW debug tool

A few years ago I designed a small prototype board to allow access to
an FPGA internal registers via a single bi-directional pin.

This replaces an RS232 type interface but is USB driven so removes the
need for external power supplies for level shifters etc.

This has been invaluable, I've used it with almost every board I have designed
over the last few years, so I have developed the prototype and have come up
with the 1 Pin Interface...


www.1pin-interface.com


This allows easy access to an FPGAs status or control registers via a
simple Excel driven interface.


Any comments, questions or orders are welcome.



Nial

----------------------------------------------------------
Nial Stewart Developments Ltd        Tel: +44 131 516 8883
32/12 Hardengreen Business Park      Fax: +44 131 663 8771
Dalkeith, Midlothian
EH22 3NX
www.nialstewartdevelopments.co.uk

> www.1pin-interface.com

I've been emailed to say that some people are having problems with this.

This is based on a Tiddlywiki, a quick google shows that the Skype plug-in
breaks some wiki-sites. It's in the Skype bug list to be fixed.

If you do have any problems try disabling Skype to view it.


Hardly an auspicious start. :-(


Nial

On Mar 4, 5:31=A0am, "Nial Stewart"
<nial*REMOVE_TH...@nialstewartdevelopments.co.uk> wrote:
> >www.1pin-interface.com
>
> I've been emailed to say that some people are having problems with this.
>
> This is based on a Tiddlywiki, a quick google shows that the Skype plug-i=
n
> breaks some wiki-sites. It's in the Skype bug list to be fixed.
>
> If you do have any problems try disabling Skype to view it.
>
> Hardly an auspicious start. :-(
>
> Nial

Looks interesting. A few administrative observations:

* I get '404' pages for the target VHDL and Schematics on the Download
pages.
* the links in your prior messages are missing the 'http://' so they
need to be cut/pasted into the browser rather than just clicking to
follow.

Conceptually attractive - I like the idea of an inexpensive USB
interface for internal access to FPGAs. Something along the lines of
Chipscope. I don't much care for the need to use Excel as the front-
end. For those of us who don't use Excel or have access to VBA is
there any possibility of a document that describes the protocol so
that other languages & apps can be used to access it, or is that level
of detail proprietary?

Eric

> Looks interesting. A few administrative observations:
> * I get '404' pages for the target VHDL and Schematics on the Download
> pages.

This should be mostly fixed, I don't seem to be able to link to a *.vhd
file for some reason but have changed it to *.txt. Just change the file
ending and it should work.

I'll try it fix it properly later.

> * the links in your prior messages are missing the 'http://' so they
> need to be cut/pasted into the browser rather than just clicking to
> follow.

It looks like this is a Google problem, other newsreaders pick up the
URLs properly, but thanks again.

> Conceptually attractive - I like the idea of an inexpensive USB
> interface for internal access to FPGAs. Something along the lines of
> Chipscope.

Yes, but at a slightly higher functional level.

Chipscope/Signal Tap are for monitoring individual lines/groups (AFAIK).

The 1 Pin Interface is more targeted towards reading or driving
status or control registers.

The idea is to have a convenient/compact interface that replaces
an RS232 type debug interface and removes the need for external
power supplies for level convertors etc. And only uses one pin.

> I don't much care for the need to use Excel as the front-
> end.

I started using C++ builder but switched to Excel because it's
almost universal. BTW, if you have access to Excel the VBA editor
is integrated, just hit Alt-F11.

It's obviously not universal enough!

>  For those of us who don't use Excel or have access to VBA is
> there any possibility of a document that describes the protocol so
> that other languages & apps can be used to access it, or is that level
> of detail proprietary?

Yes no problem, I want to to be as open as possible, as long as you
don't expect support for strange languages. I'll probably publish the
code for the 1 pin module if there's any demand.

I'll add a page to the Web site lising the text of the Excel module
tonight. This is probably the simplest way of explaining what's happening.


Thanks for the feedback.

Nial

On Mar 4, 10:06=A0am, "Nial Stewart"
<nial*REMOVE_TH...@nialstewartdevelopments.co.uk> wrote:
> > Looks interesting. A few administrative observations:
> > * I get '404' pages for the target VHDL and Schematics on the Download
> > pages.
>
> This should be mostly fixed, I don't seem to be able to link to a *.vhd
> file for some reason but have changed it to *.txt. Just change the file
> ending and it should work.

Yep - I'm now able to get both of those items.

> > Conceptually attractive - I like the idea of an inexpensive USB
> > interface for internal access to FPGAs. Something along the lines of
> > Chipscope.
>
> Yes, but at a slightly higher functional level.
>
> Chipscope/Signal Tap are for monitoring individual lines/groups (AFAIK).

Yes, now that I've seen the way the target works it appears to be a 4k
bank of 16-bit read/write registers. Chipscope gives a more fine-
grained access than that, although one can build similar structures in
the GUI. Any other debugging function (bit access, logic analyzers,
etc) could be easily layered on top of the register structure so it's
functionally complete.

As I've mentioned elsewhere, one of my gripes with Chipscope is that
all access to the Virtual I/O and Internal Logic Analyzers is mediated
by their WinXX GUI app, and that can't be scripted or controlled by
anything except user mouse clicks. They have a rudimentary TCL
interface, but it doesn't know how to access the VIOs and ILAs - it
just gives access to the JTAG TAP controller. Having algorithmic
access to the FPGA guts would be a big help, and right now I have to
do that via other means (extra logic on the board that's controlled by
the PC, etc).

> > there any possibility of a document that describes the protocol so
> > that other languages & apps can be used to access it, or is that level
> > of detail proprietary?
>
> Yes no problem, I want to to be as open as possible, as long as you
> don't expect support for strange languages. I'll probably publish the
> code for the 1 pin module if there's any demand.
>
> I'll add a page to the Web site lising the text of the Excel module
> tonight. This is probably the simplest way of explaining what's happening=
.

Sounds good. Thanks for making this available.

Eric

On Mar 5, 6:06=A0am, "Nial Stewart"
<nial*REMOVE_TH...@nialstewartdevelopments.co.uk> wrote:
> > I don't much care for the need to use Excel as the front-
> > end.
>
> I started using C++ builder but switched to Excel because it's
> almost universal. BTW, if you have access to Excel the VBA editor
> is integrated, just hit Alt-F11.
>
> It's obviously not universal enough!

So, does it work with OpenOffice ?


> Yes no problem, I want to to be as open as possible, as long as you
> don't expect support for strange languages. I'll probably publish the
> code for the 1 pin module if there's any demand.

I could not see an example timing/protocol diagram ?

The other uses that spring to mind are

* Use with a Microcontroller, in which case a SW-pin version on the
target would be needed.
Might be as simple as a slow enough clock ?

* Use with CPLDs, in this case, minimal-logic is the requirement.

-jg

> > Yes, but at a slightly higher functional level.
> > Chipscope/Signal Tap are for monitoring individual lines/groups (AFAIK).

> Yes, now that I've seen the way the target works it appears to be a 4k
> bank of 16-bit read/write registers.

Yes, but you only need to implement the address span and data depth in
the Target FPGA that's required.

I've often used it with fewer than 8 target registers.

Your synthesis tool should then optimise out any logic that isn't
required.

> > I'll add a page to the Web site lising the text of the Excel module
> > tonight. This is probably the simplest way of explaining what's happening.

> Sounds good. Thanks for making this available.


OK, it's not a seperate page but I've added the VBA OnePinModule as
a text file in Downloads with a note in Host Software.

Please no sniggering about my software 'prowess', it took me a while to
get it all going.


Nial

> > It's obviously not universal enough!
> So, does it work with OpenOffice ?

No, the OpenOffice spreadsheet doesn't have any VBA capability as fair
as I'm aware.

> I could not see an example timing/protocol diagram ?

It's _very_ simple.

If you look at the Quick Start Guide section of the web page you'll
see the process in the target FPGA that implements the read and
writes functionality.

That's all you need to worry about, all the rest of the functionality
_should_ work end to end.

(I can add a Modelsim screen capture to deomonstrate this but it's so
simple this shouldn't be needed).


> The other uses that spring to mind are
> * Use with a Microcontroller, in which case a SW-pin version on the
> target would be needed.
> Might be as simple as a slow enough clock ?

Aye perhaps, but do most uCs not have decent in-circuit debuggers
etc these days?


The serial clock speed is set via a constant in the 1 Pin Module design.
This could be changed to something that can be set with an internal
write, but I had to decide on a set of functionality to get done and
tested and this was way down the list.

> * Use with CPLDs, in this case, minimal-logic is the requirement.

A minimal set of registers can be implemented in the target logic with about
170 logic elements.

The interface could be modified to only transfer 1 byte at a time to
reduce this further but there will be a limit as to how small it can
be got and there probably aren't that many more designs that will be
enabled by doing this.

Again it was a question of drawing a line in the sand to get it done and
tested.

If you need something much smaller the 1 Pin Interface probably isn't your
solution.


Thanks for the feedback/queries,


Nial.

On Mar 5, 10:30=A0am, "Nial Stewart"

>(I can add a Modelsim screen capture to deomonstrate this but it's so simp=
le this shouldn't be needed).

That could help broaden the use.

> > The other uses that spring to mind are
> > * Use with a Microcontroller, in which case a SW-pin version on the
> > target would be needed.
> > Might be as simple as a slow enough clock ?
>
> Aye perhaps, but do most uCs not have decent in-circuit debuggers
> etc these days?

 Yes, but they do not all include communications channels, and it is
quite rare to access the debug Flow from user code.

 There are numerous instances where a simple PC access to an operating
embedded system, would be nice to have, (and the UART may be already
committed.)

-jg

On Mar 5, 10:15=A0am, "Nial Stewart" >
> OK, it's not a seperate page but I've added the VBA OnePinModule as
> a text file in Downloads with a note in Host Software.

I had a quick look - what is this file called ?

-jg