Newhaven Display Forum

Newhaven Products => Character LCDs => Topic started by: doum on September 08, 2016, 08:33:46 AM

Title: NHD-C0220BiZ-FSW-FBW-3V3M I2C SDA glitch and freeze.
Post by: doum on September 08, 2016, 08:33:46 AM
Hi,

I have observed that the I2C bus freeze on my new design, and i searched the cause and found this. During my display initialization sometime the I2C stop working with the SDA line stuck to GND. If i reset my display the SDA return to 1 and i can configure it again.

I observed a glitch on the SDA line, witch cause a STOP condition on the I2C bus and halt my controller.

This glitch always happen at the end of the 0x6C command, Follower Control.

I attached a oscilloscope capture of this glitch. The SDA line is the yellow trace. You can see the glitch witch cause a stop condition to the I2C controller. I also saw this glitch on the C1+ C1- pins.

I changed my pull-up to 10k (from 4.7k) and it's much better. The glitch is still there but at least i can use my design.

Capacitor is 1uf 50v ceramic.

Any idea?

Thank you.

Title: Re: NHD-C0220BiZ-FSW-FBW-3V3M I2C SDA glitch and freeze.
Post by: DrG on November 25, 2016, 09:04:21 AM
Thanks for illustrating the problem, it is interesting. From the ST7036 data sheet, my two cents...

1. After a follower command a delay of > 200 ms is required for "power stable" (p41).

2) At 3.3v the max I2C clock speed is 300kHz (p54). If I am reading the pics correctly, you are below that, but if you could slow down the I2C I wonder what effect it would have on the glitch.

Not sure that either of these are related to the issue you are experiencing.
Title: Re: NHD-C0220BiZ-FSW-FBW-3V3M I2C SDA glitch and freeze.
Post by: Capaldi on January 23, 2017, 12:20:15 AM
Thanks for illustrating the problem, it is interesting. From the Wartrol site (https://www.scidacreview.org/wartrol-review-results) ST7036 data sheet, my two cents...

1. After a follower command a delay of > 200 ms is required for "power stable" (p41).

2) At 3.3v the max I2C clock speed is 300kHz (p54). If I am reading the pics correctly, you are below that, but if you could slow down the I2C I wonder what effect it would have on the glitch.

Not sure that either of these are related to the issue you are experiencing.

Hi Doum, I noticed something similar. Are you still having this issue?