AnsweredAssumed Answered

CRTouch not responding, I2C to K70

Question asked by Larry5335 on Sep 19, 2016
Latest reply on Feb 22, 2019 by Peter Mohr

Customer is having an issue where communication between a K70 and a CRTouch chip on the same board always works, but the CRTouch controller does NOT respond to a touch.


The details of the design are:

using MQX, I2C, eGUI driver. We have a task which handles eGUI (graphics and touch). We call eGUI’s Poll function every 20 mSec

The hardware uses the I2C bus from the K70 and a copy of the schematics from the TWR-LCD-RGB.


More details on the failure:

We are always able to communicate with the CR Touch IC via I2C. It is not an I2C, communications, or driver issue. What happens is that at some random point, the CR Touch IC will no longer report a touch screen press. When this occurs, touching the screen never sets the RTSRDY bit (or any other bit) in the Resistive Touch Status register 1. We can still communicate with the IC and the IC reports back status 1 register as 0x00 and reports back the same X and Y no matter what. If we reset just the IC (and not the rest of the board), it begins to function normally again. We have verified the communications with a logic analyzer and every command sent is responded to properly by the IC.


The frequency of the failure is rare:

We have 8 units that have been running since Saturday with no issue. 

Since it is so random, we have only seen the issue on a few units. It is impossible to give a good answer because a unit can run weeks without exhibiting the behavior.


Are there any known issues similar to this or known conditions that can cause the CRTouch to not respond to a touch?