Hello,
I tested some samples of mcufriend on MEGA (no SD card used) and compared to the UNO, it's up 3,5 times slower! Is there a workaround?
It seems it also depends of the firmware, I tried HX8347 on MEGA, it is about 1,5 times slower... so 5 times slower than the ILI9341 on UNO!
Yes, of course the Mega2560 will be much slower when it is running a UNO shield. e.g. tractor pushColors() is 149ms vs 60ms
If you want to go fast on a MEGA2560 buy a Mega2560 shield. (which will not fit on a Uno)
It comes down to the data bus on Uno shields. LCD_D0-LCD_D7 are sensible pins on PORTB, PORTD for a Uno. Random pins on a Mega.
And HX8347 is always going to be slower than either ILI9320 or ILI9341 style controllers.
David.
Edit. The purpose of this example is to demonstrate the Adafruit_GFX methods
e.g. drawing monochrome images with different foreground colour and background.
e.g. drawing RGB images
e.g. with masks
The Adafruit_GFX methods simply draw individual pixels. Hence the flexibility but slowness.
The pushColors() examples use the hardware to display solid rectangular images.
Thanks for you answer.
(1) is a ProtoShield. Solder an 18x2 female header. You can re-route the data bus to D22-D29 on the 2x18. Cut the copper traces from the original data bus.
There is a SPECIAL for this. It will work FASTER than the Uno. i.e. USE_MEGA_8BIT_PROTOSHIELD
There are several ready-made Display Shields for the Mega2560. Most use a 16-bit bus. There is a SPECIAL for 16-bit Shields. i.e. USE_MEGA_16BIT_SHIELD
Your Uno Display Shield is read-write and continues to be read-write with the Protoshield.
The Mega Display Shields are always write-only.
David.
Not sure to understand all the procedure but, I need to buy so I googled to buy a ready-made 16-bits bus Display Shields for the Mega2560 but I did'nt find no one 
Search for "320x480 Mega2560 Touch" on Ebay, ...
Note that a Mega Shield has 18x2 header that mates with MEGA2560.
Displays with 16x2, 17x2, 20x2 headers all require Adapters with level shifters.
David.
Ah ok, there's a misunderstood, I thought you spoke about a special shield, a sort of adaptor for my case. Although, I didn't know there're other kind of TFT with 18x2 headers specially adapted for the Mega. It's interesting, thanks! I order one that I will test.
But for now, I still would like to make work this screen on the Mega because all my codes are for that resolution (320x240) and this specific size of the screen.
So I connected the screen on the Mega with Dupond wires:
LCD_D0 -> D22
LCD_D1 -> D23
LCD_D2 -> D24
LCD_D3 -> D25
LCD_D4 -> D26
LCD_D5 -> D27
LCD_D6 -> D28
LCD_D7 -> D29
Here's I kept the UNO pinout:
LCD_RD -> A0
LCD_WR -> A1
LCD_RS -> A2
LCD_CS -> A3
LCD_RST -> A4
I uncommented SPECIAL in "mcufriend_shied.h", then I uncommented one after the other in "mcufriend_special.h":
USE_MEGA_8BIT_PROTOSHIELD
USE_MEGA_8BIT_SHIELD
USE_MEGA_8BIT_PORTC_SHIELD
=> WHITE SCREEN
Now I changed this part of the wiring:
LCD_RD -> A0 (I didn't change it, I don't know where else)
LCD_WR -> 39
LCD_RS -> 38
LCD_CS -> 40
LCD_RST -> 41
Then I tried again to uncomment the previous USE_MEGA_8BIT_ but I still have a white screen.
I don't know what I could try else.
So I connected the screen on the Mega with Dupont wires:
LCD_D0 -> D22
LCD_D1 -> D23
LCD_D2 -> D24
LCD_D3 -> D25
LCD_D4 -> D26
LCD_D5 -> D27
LCD_D6 -> D28
LCD_D7 -> D29Here's I kept the UNO pinout:
LCD_RD -> A0
LCD_WR -> A1
LCD_RS -> A2
LCD_CS -> A3
LCD_RST -> A4I uncommented #define USE_SPECIAL in "mcufriend_shield.h", then I uncommented only one after the other in "mcufriend_special.h":
#define USE_MEGA_8BIT_PROTOSHIELD
is correct. Obviously your Dupont wires should be good. And you should connect 3.3V, 5V, GND pins.
Personally, I would only be happy with a soldered ProtoShield.
Hey-ho. YMMV.
David.
Wow! It works, I had inverted two bus wires (Do with D1) ! The sample test shows that it's slightly faster than the UNO now!
I have a last problem, there's no touch anymore. I tried the "TouchScreen_Calibr_native" sketch and I get the message "Broken touchscreen". The same error with a second screen to check.
I always used the following on UNO:
#include <TouchScreen.h>
#define YP A3
#define XM A2
#define YM 9
#define XP 8
MCUFRIEND_kbv tft;
TouchScreen ts=TouchScreen(XP,YP,XM,YM,364);
I need to change these constants by which values?
I strongly recommend using const assignments like my examples.
YM = 23
XP = 22
You could edit the Calibration sketch to search 22-29 as well as 2-9
Great! Your values work on MEGA, no need calibration. I just noticed I need to add a small pressure or reduce the r value, about 300 instead of 364 to have the same feeling.
Thank you very much!
