Problem implementing the touch interface part of a RA8875 LCD touch display

Hi all,

I am programming a 5 inch display bought in buydisplay (https://www.buydisplay.com/5-inch-tft-lcd-module-800x480-display-controller-i2c-serial-spi) which has a RA8875 chip and a capacitive touch panel (both use the I2C protocol), and even though I have been able to write text for example, I am struggling trying to implement the code for the touch part, and looking the datasheet I am not able to see what I am doing wrong.

I know or think so which registers I have to write to or read from, but what I don't t know is the chip I have to use for the touch part. If as I guess it is the one connected to the ZIF cable, do you know its address? And also, do you know which registers regarding the touch interface have to be used and which ones from the RA8875?


Regards,
Javier

P.S.: Let me know if you need a further explanation or some other data in order to know better about the issue.

Did you look through all of the docs on that site? For example, the C code seems to indicate the address - no?

#define TI2C_ADDR 0x80
#define TI2C_CLK 300
#define MAX_CONTACTS 10
#define MULTI_TP_POINTS 10

Hi DrG,
I read the code examples and the datasheet part but for what you show here looks like I missed that address (I found the ones to read and write commands or data, but not for the touch interface).

I will try with that address and see if it works.


Thanks,
Javier

Hi again DrG,

You were right. After some further research I realised that I was confusing the optional touch interface with another one, which code example appears in the RA8875 datasheet.


Thanks,
Javier

Good deal. I actually like that site quite a bit. Some displays may be a bit higher than elsewhere, but their practice seems to be to link the data sheet and some code samples (usually 8051, but in C).

Please do keep us informed about your progress and experiences with that display and the touch element. It did look pretty interesting, and I see a lot of coding in your future