TSC2007: TSC2007

Hi,

Please wait until Monday Sep 26th for our haptics expert to comment. 

Thank you for your patience

Thanks,  Daveon Douglas , during a subsequent check,  an  unexpected 2.5ms width was observed on the PENIRQ, which is much longer than "usually in nanoseconds" described in slyt292. does this impact the correct output ? 

Hi Nick,

Apologies for the delay once again, I have assigned our audio expert Sanjay to your question. Please wait for him to comment

Are you using PENIRQ in your processor? If you disable this with command Byte, does the pin still show this pulse

Yes, PENIRQ is used to send interrupt signal to CPU.  it is disabled every time data processing starts and re-enabled at the end of data processing. 

Shall analyse and respond on monday

Any updates?

Shall respond in a few hours.

This seems to be happening when Y+ and Y- are at zero volts . This means that the Panel is not driven by any Voltage coming from the Chip. Its possible that the Purple spike is something picked up externally on the touch screen. 

Are there any noise suppression Capacitors present on the touch screen pins. Perhaps 1n values could be placed to see if any change happens

yes, 10nF value has already been used for X+, X-, Y+, Y- respectively. we also tried other values like 100pF , 1nF, the behavior can still be observed.  in some worse cases, you can see data is even not stable before data is captured ( see picture below ) . 

Can you let me know what Y+ and Y- are at the time you see this slow rise of X+?

We did not have enough channels , , you can see below also the slow rise of Y identified . 

Are you attempting to read both X and Y Coordinates in this I2C Burst?

Can you attempt to read just Y Position (shown with red arrow). This will only activate a drive on y drivers and you read Y position through X. Does this waveform change if we do so? Do you make a perfect vertical line if we try only this command?

Also you could disconnect X +from the chip during this test and see the waveform

Thanks for your reply. Yes, we are using serial-production software to read both X and Y coordinates.  does your suggestion mean we have to modify the software driver to do the test (Read just Y position)? currently we do not have the tools to customize these configurations by software, could it be done by hardware adaptions only ?  another question is since similar behavior was observed on both X, Y, may I know why you suggest reading just Y position?  Thanks !

I just want to try to understand what you are seeing here.

Without changing the code i would suggest to disconnect X+ and X- from the Chip. When the Y coordinates are measured, Y+ will go High and Y-shall go Low. During this time  X + should be a DC Voltage that goes from 0 to3v as we start touching the screen from top to bottom. When Y+ and Y- are low the X+ Voltage should fall to zero.

See if this level is consistent for many scans.

The similar can be checked for X 

Hi Sanjay Dixit, unfortunately, without changing the code, we did not manage to do the abovementioned measurement, I hereby attach all the measurement data that we were able to arrange on our side for you reference, in which you can see the jumping happens on X, Y coordinates with different filter capacitor being used, even when TSC2007 is powered by a standalone DC.  meanwhile, the same behavior was observed on different touch screen supplier, it looks it is more related to touch controller ......  did you ever meet this issue before and how it was solved?  if you could provide a list of possible solutions or recommendations (either software or hardware), it would be really helpful. I am looking forward to feedback!

TSC2007_DrawTest.pdf  

The Test i requested only needed the X,Y pins to be disconnected.. You can do in existing setup

Just double check: when removing X and reading Y coordinates ,  how to power on the Y+ /Y-, using existing TSC2007 or standalone DC power supply?  if the former, it looks once X is removed, Y+/Y- driving signal is also not possible from TSC2007.   

i Would suggest to keep Y+/Y- pins connected on the chip and to disconnect X+/X- pins

from the chip

In this situation the chip would periodically power Y+/Y- Pins.if we place an Oscilloscope on X+Pin we shoukd see a voltage which goes from 0v-3v as we move our finger top to bottom

yes, we tried just as you suggested,  unfortunately , we did not see the chip periodically power Y+/Y- pins, thus cannot see the abovementioned expected behavior,  it looks coding has to be adapted to for this test.  by the way, in page 5 of the PDF file I shared previously , you can see Z value goes up as pressure increases ...... besides this, do you have any other proposals ?  

I

The schematic indicates the setup I had in mind.