# I2C decoding concern

**URL:** <https://discuss.saleae.com/t/i2c-decoding-concern/1133>\
**Category:** Logic 2 Software\
**Created:** [August 23, 2021, 9:33pm UTC](https://discuss.saleae.com/t/i2c-decoding-concern/1133 "2021-08-23T21:33:21Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![gansler](https://avatars.discourse-cdn.com/v4/letter/g/edb3f5/32.png) [@gansler](https://discuss.saleae.com/u/gansler)\
**Post date:** [August 23, 2021, 9:33pm UTC](https://discuss.saleae.com/t/i2c-decoding-concern/1133/1 "2021-08-23T21:33:22Z")

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I2C decoding here looks spot on:

 ![image](https://canada1.discourse-cdn.com/flex030/uploads/saleae/original/1X/0cfea53ef4b3c011eff2a21b6539d0238b7176ea.png)

I2C decoding on the 2nd I2C peripheral looks incorrect. Take a look at how its interpreting the bits of the address incorrectly, the first data byte incorrectly, and the ACK/NACK wrong. And the up-arrows on the SCL rising edges are missing? Maybe I’m missing something - it’s been a long day. 😃

 ![image](https://canada1.discourse-cdn.com/flex030/uploads/saleae/original/1X/971c9ab358726f1350ad14d55b048d924971f4da.png)

This is running 2.3.34 with a Logic Pro 16.

-Mike

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**Author:** ![timreyes](https://yyz2.discourse-cdn.com/flex030/user_avatar/discuss.saleae.com/timreyes/32/108_2.png) [@timreyes](https://discuss.saleae.com/u/timreyes)\
**Post date:** [August 23, 2021, 10:48pm UTC](https://discuss.saleae.com/t/i2c-decoding-concern/1133/2 "2021-08-23T22:48:02Z")

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Hi Mike,

Sorry to hear about this! Based on the image you shared, I suspect there may be glitches present in your SCL line (I notice a think rising edge in your SCL signal). Glitches will cause the analyzer to think there are multiple rising edges, which causes decoding errors.  
 ![Screen Shot 2021-08-23 at 5.43.31 PM](https://canada1.discourse-cdn.com/flex030/uploads/saleae/original/1X/112b3a146c7225cd4610c57d4811ef130d5b1477.png)

Can you try implementing a glitch filter as per the instructions below in your next capture?

> **[Software Glitch Filter](https://support.saleae.com/user-guide/using-logic/software-glitch-filter)**

The up arrows missing are strange though. Once you try out the glitch filter, and if you’re still seeing issues, would you mind doing the following?

- Download Logic 2.3.35 (we just released it to add a few quick bug fixes we found)  
[Logic analyzer software from Saleae](https://www.saleae.com/downloads/)
- Send me a copy of your .sal capture file if the above tips fail to help:  
[Capture & Preset File Management - Saleae Support](https://support.saleae.com/user-guide/using-logic/saving-loading-and-exporting-data)

Looking forward to hearing back!

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<div class="post-metadata">

**Author:** ![gansler](https://avatars.discourse-cdn.com/v4/letter/g/edb3f5/32.png) [@gansler](https://discuss.saleae.com/u/gansler)\
**Post date:** [August 24, 2021, 6:46pm UTC](https://discuss.saleae.com/t/i2c-decoding-concern/1133/3 "2021-08-24T18:46:37Z")

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Mike - thanks for the quick response!

I downloaded 2.3.35 and enabled 100 nsec of glitch filtering. No decoding issues seen since and up/down arrows are being displayed again on the SCL signal.

I really love being able to enable analog mode too to see what’s going on. Great feature and good eye noticing those double edges!

Thanks,

-Mike

Example of things looking good again:

 ![image](https://canada1.discourse-cdn.com/flex030/uploads/saleae/original/1X/365411cd1e6d83d575b082473d984df5bfbcece8.png)