I2C sniffer - Page 1
Forum section: electronics / beginners

author: Jane
author_rank: Frequent Contributor
timestamp: August 11, 2015, 08:01:34 pm
content: Can anyone recommend a good I2C sniffer?I have a logic analyzer, but a problem is that it can not capture a long enough time I would need. Is there any way how to capture long enough time period I need?Thanks

author: rx8pilot
author_rank: Super Contributor
timestamp: August 11, 2015, 08:37:39 pm
content: What are you trying to sniff? Are you trying to trigger on a specific data definition?Bus Pirate maybe?

author: RogerRowland
author_rank: Regular Contributor
timestamp: August 12, 2015, 04:42:28 am
content: How much do you want to spend? I would say bus pirate too, and will be useful anyway, but if you want to spend more, then something like the Intronix Logicport would be more than enough for your needs -http://www.pctestinstruments.com/

author: Mr.B
author_rank: Unknown
timestamp: August 12, 2015, 04:46:28 am
content: I have a Saleae Logic.I find it exceptionally good.I cannot remember how much it was. Got it a couple of years ago now.

author: TiN
author_rank: Super Contributor
timestamp: August 12, 2015, 04:58:56 am
content: Or you can setup your LA to store only only edge changes, this way it would not use up memory for all those same-level samples, if your analyzer supports this mode.

author: hamster_nz
author_rank: Super Contributor
timestamp: August 12, 2015, 06:49:45 am
content: +1 on Saleae. I used a friends $10 clone and that was so good I am saving up for one.The originals are very nice, carry bag, clips etc.

author: tipofthesowrd
author_rank: Contributor
timestamp: August 12, 2015, 06:53:48 am
content: If this is for a professional environment I'd recommend the Totalphase Beaglehttp://www.totalphase.com/products/beagle-i2cspi/Much more pricey then the other suggestions but the software is excellent and the software and pre & post filtering options are excellent.

author: cyr
author_rank: Frequent Contributor
timestamp: August 12, 2015, 07:22:20 am
content: +1 for the Beagle, if you have the budget for it.

author: Mr.B
author_rank: Unknown
timestamp: August 12, 2015, 07:29:33 am
content: Quote from: cyr on August 12, 2015, 07:22:20 amJust interested...What makes the Beagle so much better than the Saleae?Saleae has excellent software and can do multiple protocols...

author: tipofthesowrd
author_rank: Contributor
timestamp: August 12, 2015, 08:34:29 am
content: Quote from: Mr.B on August 12, 2015, 07:29:33 amThe Beagle is much more of a I2C/SPI protocol analyzer then the Saleae (which is more a generic logic analyzer).The main view for example of the Beagle is based on listing all the transactions with their data, valid ACK, timing details etc. You could view the timing diagram if a single transaction if you wanted. For example if you're debugging a complex i2c device (say a DVB decoder or audio processing peripheral) you can easily spot a faulty transaction and capture the commands proceeding it etc.You 'capture' i2c packets, not generic bit data.The main screen of the Saleae on the other hand is that of a simple logic analyzer. Which does the protocol analyzing as a pure post processing step.

author: cyr
author_rank: Frequent Contributor
timestamp: August 12, 2015, 08:55:16 am
content: Quote from: Mr.B on August 12, 2015, 07:29:33 amI have not used the Saleae, but from what I understand it's like any logic analyzer with a basic protocol decoder.The beagle is a special purpose tool that allows you to very easily filter, and search through gigs of captured traffic for specific conditions like "any write to slave 0x48 of no more than 12 bytes, containing the data 0xAA, that took more than 100ms to complete".Great debugging tool.

author: hamster_nz
author_rank: Super Contributor
timestamp: August 12, 2015, 09:43:36 am
content: Quote from: cyr on August 12, 2015, 08:55:16 amThe good thing about the Saleae is that the capture length is limited to available hard disk space, and it does all the decoding on the PC. You can literally capture days worth of data if you have and then review it looking for that once-a-day glitch.

author: Mr.B
author_rank: Unknown
timestamp: August 12, 2015, 10:27:56 am
content: @tipofthesowrd and @cyr...Thanks for the response.I have only ever had the need to analyse the stream after the event.As @hamster_nz says, the software is fantastic for storage depth and the ability to analyse vast quantities of logged data.Of course, a reasonably powerful PC assists this process...

author: rx8pilot
author_rank: Super Contributor
timestamp: August 13, 2015, 10:31:10 pm
content: Quote from: tipofthesowrd on August 12, 2015, 06:53:48 amI think I will get on of these to replace my Saleae. The Saleae is a decent little box for capture, but the software is very basic. There is no way to filter in real time of trigger of of a defined data event. In my applications, I need to monitor for various errors or alarms over long periods of time and the Saleae system is not able to help me there.For $330, the Beagle seems to be a serious bargain.