Fix the I2C protocol display

david c

In I2C captures, I see the device address shift between 7 bit and 8 bit mode from transmission to transmission. i always have to go to the SCL and SDA to check things.

on a positive note, I LOVE the new measurement window where the drag and highlight over a bunch of clocks instantly shows freq and #rising and falling edges. This is so good it is almost worth buying a device just to have this capability.


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david c

Hi Tim,

What I mean by that is sometimes on the device address if I have a high on the 4th clock with SDA, then the protocol will say the device address is 0x08, and sometimes it will show 0x10. it also misses the ACK/NACK sometimes. Whenever there is something which looks strange, the SDA relative to the clock is always right, but in about 5% of the cases that bit pattern is decoded incorrectly. It's not that big of a deal. This analyzer I am using every day, and I have gotten Honeywell to buy over 10 of these in the last year or so. And, everybody loves them. I am thinking about getting a pro8 as a backup because that is my #1 tool. I would LOVE to see a pro 4 CH device just to look at UART, SPI, or I2C, because the 8CH pro is a little steep, especially since I own 4 Saleaes myself already.

Thanks Tim, Dave bassett



This sounds like glitches on the clock line to me. Try zooming in on the clock edges to see if there is an extra pulse on an edge around the faulty address bit. It can also help to turn on an analog trace for the clock line and see of the rise and fall times are unduly long.



Sorry for the trouble with the I2C analyzer. Can you explain a bit more about what you mean by the device address constantly shifting?

The I2C analyzer only natively supports 7-bit mode, while 8-bit mode is supported via an extension below:

Only one mode can be active at a time, and our I2C analyzer doesn't support changing between modes mid-capture.


david c

Hi Tim

I'll see if I can get you a snagit of what I am talking about. And, NO, this is not clock glitches. It is clear what the problem is.