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2 years ago.
I can´t get my cap touch to work
I cant get my cap touch to work on my 5" RA8875 display. I have read somewhere that the I2C cabels must be kept really short and mine are like 20cm.
Can this be the reason for my problems with the cap touch? The display seem to work fine but no touch.
I have checked my wiring and found no errors, i will re-check again to be sure.
Update: My SPI signals looks strange:
I´m new to measuring with a scope so im happy i managed to get this pic. Ch1 Yellow is I2C clock SCL Ch2 Lightbule Is data SDA Ch3 Magenta is CTS interrupt
It show the I2C runs at 367,6kHz that seems wrong. And no data on the interrupt pin so i dont get notified when i touch the screen. Also the signals doesn´t look good, just like if the speed was to high. Maybe i just measured wrong.
I must try find a older firmware for the LPC1678.
Question relating to:
2 years ago.
Are you using the same pin assignment as shown on the RA8875 page?
I2C, as a shared-IO bus, uses open-drain technology to permit multiple devices to share the interface. So, you may need to add pull-up resistors to the SDA and SCL pins. These Rs might be on the RA8875 display PCB, or perhaps not. If you have a pair of resistors somewhere between 2.7K and 27K, connect one side to SDA and the other side to the Vdd of your display. Do the same with SCL. The value isn't too critical, except that you have them.