I2C monitor

[Kari Laine]

Hi,

I have been thinking about how to connect to I2C bus, so that I can see
whole activity going on. Maybe I should set the max speed requirement to
400k but the highest speed of about 3.5M would be nice.

Those analyzers are very expensive - over $1000. What makes them so
expensive? Would it be possible to connect high impedance probe to SDA
and SCL lines and write a program for FPGA to read them and transfer
data to PC using USB? What kind of probe would be needed (consisting
which parts)? I have the Logic, which is quite nice and was not very
expensive. It knows I2C and SPI but it can just analyze.

I would like also to be able to send stuff from PC to I2C lines.

Although a full solution would be highly appreciated )
I am after main points. Which components to use and how to implement
high impedance two way connection to SDA and SCL lines.

I hope this is not too vague....

Best Regards
Kari


--
PIC - ARM - Microcontrollers - I2C - SPI
Keypads - USB-RS232 - USB-I2C - Accessories
http://www.byvac.com
I am just a happy customer
Btw. They now have graphics display with TOUCH !

 

[Rich Webb]

On Thu, 26 Aug 2010 23:27:06 +0300, Kari Laine <klaine8@gmail.com>
wrote:

Hi,

I have been thinking about how to connect to I2C bus, so that I can see
whole activity going on. Maybe I should set the max speed requirement to
400k but the highest speed of about 3.5M would be nice.

I use the Intronix Logicport USB logic analyzer for this. It includes
templates to set up interpreters for I2C (along with SPI, async, and CAN
serial protocols). It should run up to the limit of the analyzer's
speed. You can download the interface software from
http://www.pctestinstruments.com/ and run it in demo mode without the
actual hardware piece. The Examples directory includes I2C.

I would like also to be able to send stuff from PC to I2C lines.

For this I'd just do up a small microcontroller that has an I2C
peripheral on one end and a UART for communications to a PC on the
other.

--
Rich Webb Norfolk, VA

 

[John Larkin]

On Thu, 26 Aug 2010 23:27:06 +0300, Kari Laine <klaine8@gmail.com>
wrote:

Hi,

I have been thinking about how to connect to I2C bus, so that I can see
whole activity going on. Maybe I should set the max speed requirement to
400k but the highest speed of about 3.5M would be nice.

Those analyzers are very expensive - over $1000. What makes them so
expensive? Would it be possible to connect high impedance probe to SDA
and SCL lines and write a program for FPGA to read them and transfer
data to PC using USB? What kind of probe would be needed (consisting
which parts)? I have the Logic, which is quite nice and was not very
expensive. It knows I2C and SPI but it can just analyze.

I would like also to be able to send stuff from PC to I2C lines.

Although a full solution would be highly appreciated )
I am after main points. Which components to use and how to implement
high impedance two way connection to SDA and SCL lines.

I hope this is not too vague....

Best Regards
Kari

Oscilloscope?

John

 

[Kari Laine]

On 08/27/2010 12:01 AM, Rich Webb wrote:

On Thu, 26 Aug 2010 23:27:06 +0300, Kari Laine <klaine8@gmail.com
wrote:

Hi,

I have been thinking about how to connect to I2C bus, so that I can see
whole activity going on. Maybe I should set the max speed requirement to
400k but the highest speed of about 3.5M would be nice.

I use the Intronix Logicport USB logic analyzer for this. It includes
templates to set up interpreters for I2C (along with SPI, async, and CAN
serial protocols). It should run up to the limit of the analyzer's
speed. You can download the interface software from
http://www.pctestinstruments.com/ and run it in demo mode without the
actual hardware piece. The Examples directory includes I2C.
Thanks! Went to my list of things to buy...when money arrives....

Do anyone have an idea how this thing is implemented?

I would like also to be able to send stuff from PC to I2C lines.

For this I'd just do up a small microcontroller that has an I2C
peripheral on one end and a UART for communications to a PC on the
other.

OF COURSE - how stupid of me - it does not have to be same probe for
input and output...

Best Regards
Kari

 

[Jon Kirwan]

On Thu, 26 Aug 2010 23:27:06 +0300, Kari Laine
<klaine8@gmail.com> wrote:

I have been thinking about how to connect to I2C bus, so that I can see
whole activity going on. Maybe I should set the max speed requirement to
400k but the highest speed of about 3.5M would be nice.

Those analyzers are very expensive - over $1000.

You may be able to get a decent logic analyzer for that.

What makes them so expensive?

Lack of sales?

Would it be possible to connect high impedance probe to SDA
and SCL lines and write a program for FPGA to read them and transfer
data to PC using USB? What kind of probe would be needed (consisting
which parts)? I have the Logic, which is quite nice and was not very
expensive. It knows I2C and SPI but it can just analyze.

I would like also to be able to send stuff from PC to I2C lines.

Although a full solution would be highly appreciated )
I am after main points. Which components to use and how to implement
high impedance two way connection to SDA and SCL lines.

I hope this is not too vague....

Kari, have you looked over:

http://www.i2cchip.com/

?

If so, can you describe what they don't do there that you
feel a need to have?

Jon