Touch functionality RA8875 with 7" touch display

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rudolfk
 
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Joined: Wed Mar 05, 2014 10:13 am

Touch functionality RA8875 with 7" touch display

Post by rudolfk »

Hello,
we purchased 3xRA8875 and 2x7" touch display on June 19 (INVOICE 813109).
We have just started to run the equipment – using information about the wiring from your sketches and user forum.
Fist results looked quite promising. Running the „build test“ sketch on the DUE we could see the screen colours change as intended and finally the test picture filing the upper left quarter of the screen. Touch was a bit unprecise and there was a spot in the upper right quarter that accumulated a lot of touches from around the screen.

Wiring:
VIN connect to Due 5v
GND to Due GND
SCK to Due PIN SAMX SPI PIN 3
MISO to Due PIN SAMX SPI PIN 1
MOSI to Due PIN SAMX SPI PIN 4
CS to Due PIN 10
Reset to Due PIN 9
Int to Due PIN 3

In order to improve this behavior we did run the „Tscalibration“ sketch. Running the sketch with the original 250ms delay after each testing point resulted in multiple counts of the first touch an therefore in complete disarray.
Running the sketch with a 2500ms delay gave us the chance to hit each point as intended. However, the information about the point of touch seem to be all over the place. Touching one spot on the screen now results in multiple spots created all over the screen.

We think that the resistive touch screen might not be working correctly.
Second screen works a lot better (same DUE, same RA8875). Touchpoints are off by a couple of mm offset towards the middle of the screen.
TSCalibration still creates a mess on this screen too. But fortunately the information seems to get lost after reset. (Where is the touch calibration stored and how - tscalibration says something about EEPROM?).

Please give us advise on how to proceed.

Kind regards

Rudolf

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adafruit_support_rick
 
Posts: 35092
Joined: Tue Mar 15, 2011 11:42 am

Re: Touch functionality RA8875 with 7" touch display

Post by adafruit_support_rick »

The calibration information is not stored to eeprom. That part of the ts_calibration sketch is not implemented.

Please email [email protected] with a link to this thread for a replacement screen.

rudolfk
 
Posts: 10
Joined: Wed Mar 05, 2014 10:13 am

Re: Touch functionality RA8875 with 7" touch display

Post by rudolfk »

Hello Rick,
thank you for your fast reply. I will contact support as suggested by you.
How can we calibrate the touch? So far we used HK library, where the cal data is stored in the CD.h file. Is there a similar file or lines of code in each program in the ADAFRUIT library as well? How do we retrieve the data needed for calibration?

I am totally surprised, that we can operate the 7" LCD without any external power supply. That is a first for us. The DUE does not even get warm and the picture on the screen is bright enough for our purpose - congrats on this. For long term use, would you recommend a separate power supply for the screen / what would your recommendation be for DUE power supply (with screen) through the power jack (not USB) 7VDC or more?
Does the screen support something like wake up on touch?
Thanks and best regards
Rudolf

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adafruit_support_rick
 
Posts: 35092
Joined: Tue Mar 15, 2011 11:42 am

Re: Touch functionality RA8875 with 7" touch display

Post by adafruit_support_rick »

The ts_calibration example does everything but save the calibration to eeprom. You will have to modify the calibration program to save the data.
In your regular sketch, you will have to retrieve the data from eeprom and apply it to the screen. Unfortunately, we don't have any example code for this - you will have to develop it yourself.

The Arduino EEPROM library is documented here:
https://www.arduino.cc/en/Reference/EEPROM

You can use an external power supply with the screen, or you can continue to power it from the Due. If you attach more devices to the Due, you may want to go with the external supply to avoid overloading the Due's voltage regulator.

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adafruit2
 
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Re: Touch functionality RA8875 with 7" touch display

Post by adafruit2 »

The RA8875 touch capability is not well documented, and its kinda 'iffy' - you may want to use a seperate touchscreen controller or the adafruit analog 'touchscreen' driver - the Due has tons of analog pins and can handle the calibration easily https://github.com/adafruit/Touch-Screen-Library

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