MCUFRIEND 320x480 Calibration problem

[pratto]

I currently have a 3.5" 320x480 TFT ili 9486 display working like a charm with my MEGA. i am so pleased with this combination that i ordered another pair. i made sure the display was an ili 9486, and had the same pinout on the shield. the shield looks just like the other one. it says compatible with UTFT/UTFT_Buttons/UTouch Library for Arduino.

they came in, so i decided to test the new display first with a known good configuration. I had my original setup running. i powered down, unplugged the known good display/shield from the known good MEGA. i plugged the new display/shield in, and powered up and re up-loaded. the familiar screen appeared and everything was working normally (numbers updating, etc), until i tried to use a touch screen button. there was no response at all.

So i powered down, plugged in the original display/shield back into the original MEGA, up-loaded, and everything was back working, including the screen buttons.

I plugged the new display into the new MEGA and uploaded. As with the other MEGA, the numbers update, but the screen buttons don't respond.

I decided that, despite the displays and shields looking alike, i was going to have to calibrate the new display, just as i had done with the original setup. So first I went to Examples and loaded MCUFRIEND_kbv/graphictest_kbv, and it works.

Next i loaded diagnose_Touchpins. it seemed to run and i got this on the monitor :

Making all control and bus pins INPUT_PULLUP
Typical 30k Analog pullup with corresponding pin
would read low when digital is written LOW
e.g. reads ~25 for 300R X direction
e.g. reads ~30 for 500R Y direction

Next i loaded Touch_shield_new, and it seemed to work, but the exit button would not respond. it said to Calibrate. So i loaded TouchScreen_Calibr_native. It says BROKEN TOUCHSCREEN on the monitor and on the display. unresponsive to touch.

Am i just not setting something right or is it a bad display ?
How can i further check it ?

[david_prentice]

pratto:
I currently have a 3.5" 320x480 TFT ili 9486 display working like a charm with my MEGA. i am so pleased with this combination that i ordered another pair. i made sure the display was an ili 9486, and had the same pinout on the shield. the shield looks just like the other one. it says compatible with UTFT/UTFT_Buttons/UTouch Library for Arduino.

Please provide a link to the actual display that you bought. e.g. Ebay sale page
Please provide a link to the old display that works.

There are three types of Touch Screens:

1. Simple Resistive panel. Pins called XM,XP, YM, YP. e.g. Mcufriend Uno shields
2. Intelligent Resistive controller e.g. XPT2046 (SPI)
3. Intelligent Capacitive controller e.g. FT6206 (I2C)

You need different libraries e.g.
Adafruit_TouchScreen.h for (1)
XPT2046_TouchScreen.h for (2) using Hardware SPI bus
URTouch.h for (2) using random GPIO pins
Adafruit_FT6206.h for (3)

Note that "XPT2046 displays" are cheaper when they are sold without a Touch Panel and without a XPT2046 chip.

Note that most Mega2560 40-pin Adapters or Mega2560 Shields route the XPT2046 pins to random GPIO.
So you can only use a bit-bash library like URTouch.h

Hint. A physical Resistive panel as in (1) or (2) can be recognised by a printed Gold stripe around the edge of the TFT screen with 4 printed Gold terminals going to a 4-way ribbon.
Hint. A missing XPT2046 can be recognised by an empty SOIC-16 footprint on the pcb.

David.

[pratto]

David -

thank you for your quick and thorough reply. it has been a little hectic around here. as for the ebay pages :

the first, and working display : ebay has stopped the link to my purchase item number (it was about 4 months ago), so i can only say that yes, it has the band around it leading to a 4 wire cable, and i can send a copy of the image of it that i made when i bought it. attached.

the second (and non-working display) : https://www.ebay.com/itm/US-3-5-Inch-TFT-Screen-Module-480-x-320-For-Arduino-UNO-MEGA-2560-R3-Board/202798422049?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

this second display does NOT have the gold/silver banding.

about a week ago i ordered 2 more displays : the first is one that has the same banding :
https://www.ebay.com/itm/3-5-Inch-Screen-LCD-Display-HDMI-Interface-TFT-Monitor-Module-N9G9/163957330556?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

and as nearly as i can tell, an exact match for the working display.

the second does not have the banding :
https://www.ebay.com/itm/US-3-5-Inch-TFT-Screen-Module-480-x-320-For-Arduino-UNO-MEGA-2560-R3-Board/202798422049?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

I will wait until they come in to see if the non-resistive screen is the problem.

if the banded one works, then i will just get more of them, rather than try using a new library etc. for a different type of screen. if it doesn't, damn the bad luck.

[david_prentice]

The first Ebay link says:

5. Compatible with UTFT / UTFT_Buttons / Utouch Library.

which implies a Touch panel. However it certainly is NOT Utouch compatible.
the photo shows a Touch Panel. But quite honestly I would not trust an Ebay description until the item arrives. And you can compare the item on your desk with the photos, information, ... on the Ebay sale page.

The second Ebay link says:

Specification:

Brand new

Screen Material: TFT

Module Size: approx. 5585mm/2.173.35"

Screen Size: 3.5"

Input Voltage: DC 3.3-5.5V

Resolution: 320X480

Drive IC: ILI9486

Interface Mode: parallel 8 bit

Module Pin: 28Pin (8+8+6+6)

Touch: No

Both screens seem to have AMS1117 regulators. When they arrive you can see whether there are HC245 or LVC245 buffer chips.

David.

[pratto]

ok. as soon as they come (maybe as late as june) i will test and reply.