TSC2004: Test_Bit mode

Hello Hiroshi,

I am not very familiar with the Test-Bit mode. Let me do some digging to see if I can find more information on this topic. 

As for measuring the resistance, do you mean the input impedance of the device?

Regards,

Aaron

Hi Aaron,

Thank you for your reply.

Normally, this device will measure the combined resistance of X and Y when touched. Customer questions
Is it possible to measure the resistance value when not touching?
So
　Between X + and X-
　Between Y + and Y-
Customers want this device to be able to measure two values

Regards,
Hiroshi

Hi Aaron,

I'm really sorry. 

Our customer has the following additional questions.

Q3.
if we can measure it without touch, Do you know the accuracy of the error ?
(Same as the error specifications for normal operation?)

Perhaps the test mode measures the resistance value when not touching and checks if this resistance value is within the register setup range.

Q4.
Does the register setting used for TEST Mode affect the measurement result during normal operation?
I understand that this register value is used only to make sure that the panel resistance is within the register setting range.

Is it correct?

Sincerely,
Hiroshi

Hello Hiroshi,

Looking through the data sheet, I believe the test mode measures the combined X and Y resistance when not touching.

For Q4, I wouldn't expect this to affect the measurement during normal operation. 

Regards,

Aaron

Hi Aaron-san,

Could you tell me other questions?

Our customers especially want to know Q1.

I don't think Q2 can be measured during normal operation.

I think Q3 has the same accuracy as during normal operation, but how about it?

If correct, it is clear from the DS specs.

I apologize for the inconvenience, but please confirm.

Best Regard,

Hiroshi

Hello Hiroshi,

Apologies on the delay here. The Rts value should be selected using the test mode bits. The value should be x and y panel resistance combined. It seems like the values you measured seem fairly high (combined resistance of 1Mohm).  I believe the test bit mode will help the user ensure whether the touch panel is connected or shorted and does this by measuring the X and Y panel resistance and comparing input value as you mentioned. 

When you are looking to measure the X and Y resistance, are you wanted to measure the input resistance of the touch screen controller? This will have to be measured using a meter. 

Regards,

Aaron

Aaron-san,

I'm really sorry, and thank you for your answer.

As you pointed out, the total resistance that customer said is too large. I missed important information.
We will check with you soon and report again.


＞When you are looking to measure the X and Y resistance, are you wanted to measure the input resistance of the touch screen controller? This will have to be measured using a meter. 
No, Customer simply expected to get two results  "x = 670kΩ" and "y = 410kΩ".

In other words, the purpose is to check whether the resistance value of the panel meets the customer's specifications.

I apologize for any inconvenience,  because I could not understand this device.

Apologies,

Hiroshi

Aaron-san,

Although, I made a mistake in the unit.
I apologize again.

I would like to conclude first.
Since X = 410ohm and Y = 670ohm, selecting "0.86 <Rts <1.68" resulted in X = OK and Y = OK.

So I thought all the problems were solved...

However, our customers have some questions.
I have answers to all the questions, but the customer wants TI's answer..

Q1
I believe that "0.86 <Rts <1.68" should be selected,  because the result of simply adding these two resistors is 1080ohm.

Is this correct? or  need a different calculation?

  According to the customer's report, when the above range is selected, the result of X and Y is "1", and the result is correct.
  However, in other ranges, for example, a test with "0.17 <Rtd ≤ 0.52" selected may output different results, such as "0" for the X result and "1" for the Y result.
  In addition, if a value higher than "0.86 <Rts <1.68" is selected, X, Y = "1". In other words, it means that the range of resistance values ​​that are OK is not only one.

Q2 Is the test result that selects a range different from the total of the actual resistance values ​​meaningful information?

  I think test results where the proper range is not selected should be ignored.
  The customer may expect the result to be X, Y = OK only if "0.86 <Rts <1.68" is selected.

Q3
Do we need to change the selection range for the "X" test and the "Y" test?

Q4
If this test doesn't pass, does this device not work properly?

We apologize for the inconvenience.

Best regards,

Hiroshi