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Author Topic: How to read REG_ID register  (Read 57387 times)

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Re: How to read REG_ID register
« Reply #60 on: February 07, 2022, 03:12:23 PM »


We can capture and post an example of a waveform,

One thing to check in the meantime is whether your CTP gives a low pulse on INT when you touch the screen. This low on the INT line tells the I2C Master (EVE) to generate clocks to read the data.

Also, are you using it in compatibility mode (which is set by default) rather than multi-touch?

Is your screen part of a full module (e.g. Riverdi EVE 4) or is it a touch screen panel that is separate and which you connect to your own EVE PCB?   

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Re: How to read REG_ID register
« Reply #61 on: February 07, 2022, 04:24:38 PM »

This is the same display as in my post here:
So I already measured the I2C and still have the setup on my desk.

Important points:
- without touch there is nothing on the I2C lines, you need to touch it to see traffic
- the CTP is not configured or even verified to be there by the BT817 upon reset
- the CTP (usually) just works with the default settings in compatibility mode, no settings required

And what you did not mention, did you check your supply voltages?
The RVT70HSBNWC00-B needs 235mA @ 3.3V for the logic and that only is the typical but not the maximum value.
And it needs 362mA @ 5V or 1086mA @ 3,3V for the backlight at 100%, again not the maximum values.
So depending on your available source voltage your voltage regulators need to be rather beefy.
I am using two stepdown regulators with 1,2A rating, one for each rail.
And I usually set the voltages a little higher to allow for a bit of drop over the FFC.
So my 3.3V rail for the logic is actually supplying 3.36V.
And my 5V rail for the backlight is actually supplying 5.35V.
In addition I have a 4.7µF directly placed at the logic supply pin of the FFC connector.



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Re: How to read REG_ID register
« Reply #62 on: February 08, 2022, 06:57:44 AM »

Hi ,

I tried to check the CTP (INT line) it is not giving a low pulse when I touch the screen .
I am using the compatibility mode only which is by default , I did not make any changes.
Yes the screen is part of full module EVE 4 . Its not separate.

Can you please help me resolve this

Thanks in advance.

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