3.5” tft lcd screens and a 2.8" Screen on arduino?

Projects General Guidance
1

Hey I’m using the arduino zero board I have a 3.5” tft lcd display Works great. It uses most of the pins of a uno board. One thing I wanted to do is add a second 3.5” display. Mostly all pins for the display line up however there are a few for touch that I’m not going to use in the second screen and the SS/SC pin. Now from what I remember that needs to go to another pin that is free. Is this correct? I’m including a link to my display. I didn’t buy them from Amazon but they are the same displays 3.5” tft lcd. the hardware is what I need to figure out at this point.

Joseph

2

I don't see any SS/SC pin, but I do see 4 SD card pins you can leave off. That leaves 8 pins (only one of the 3.3VDC or 5VDC) is needed.

3

@sonofcy I did manage to find a photo with the pin layout.

IMG_9279
IMG_92791170×1344 223 KB

4

That is very different than what I looked at.

5

@sonofcy It might be. It's a google search I can find online. The coding says the same thing from some library on github.

//Technical support:goodtft@163.com
// Breakout/Arduino UNO pin usage:
// LCD Data Bit :   7   6   5   4   3   2   1   0
// Uno dig. pin :   7   6   5   4   3   2   9   8
// Uno port/pin : PD7 PD6 PD5 PD4 PD3 PD2 PB1 PB0
// Mega dig. pin:  29  28  27  26  25  24  23  22
#define LCD_RD   A0
#define LCD_WR   A1     
#define LCD_RS   A2        
#define LCD_CS   A3       
#define LCD_REST A4
#define WR_MASK B00000010
#define RS_MASK B00000100
6

Be careful with the LCD_REST pin, the libraries I am familiar with will reset the display during initialization. You don’t want to reset the first display while initializing the second. I have moved that pin to the RST of the Arduino to free up the I2C bus pins on an UNO, it is only used at the start of initialization.

7

Water under the bridge, but if you had the SPI type of display, then MOSI, MISO, and CLK would be shared, and only CS and D/C would be unique (RST not used, at least for this one).

8

@DaveEvans I looked at my screen There is a Sc pin It is on the analog pin side A3. I did confirm this. It's tied to a shift register of some kind that goes to the screen. @DaveEvans My pinout is different from that screen in your link.

9

So my question is the shift registers there are two of them I'm guessing they are using the analog pins for the shift registers and the SPI pins are from D10 - D13?

10

The Amazon product description says:

Driver IC : ILI9486

Google says the ILI9486 display driver chip supports both parallel and SPI interfaces. The interface used depends on how the display module manufacturer wired the screen and the configuration pins.

And the Amazon description also says:

Module Interface : 8-bit parallel interface

If that’s true (as it seems from your image in post #3), you’re out of luck, unless you’re really good at hacking…

12

@DaveEvans I have the screen up and running. My problem is wiring up a second screen a 2.8" along side this 3.5" screen. This is the 2.8" display I have.

13

Oh, so you have one parallel and one SPI. Sounds messy. Nothing to offer on that, sorry.

14

I know nothing in parallel. Both are SPI. however the 3.5 have some shift registers to it.

15

Can you post a picture of the display that you have? What is the part number on the "shift register" chips? Note that an LC245, as shown in the link that you posted, is NOT a shift register, it is a buffer chip.

16

Hey @david_2018 You are right. I wasn't paying attention because they way it look at me looks like a shift register. My fault there sorry about that.

Meanwhile I need to figure out how to wire up this 2.8" LCD as well a long side this 3.5" screen. Got to find my resistors for the other screen.

17

The screen at post #3 has a 8bit parallel interface. It is not a SPI.

If you want to use a two screens, the task could be much easier if you use a two SPI displays.

18

The only use of the SPI bus on the 1st display is the SD card, as long as you have a pin for the select line I don't see a problem hooking up the 2nd display. The touchscreen would be the difficult part, but you stated that was not going to be used.

19

@b707 You are right. But I need a 3.5" Screen and a 2.8" or a 3.0" screen. These are the screens I bought for my project.

20

@david_2018 The problem is I need a 3.5" and a 2.8" or a3.0" screen for my project. I have both but wiring them up is a problem. the 3.5: screen uses the D8 through D13 pins and A0 through A3 pins.

21

I don't think the cost of a screen is worth the effort you'll spend combining screens with different interfaces. Even if you already have screens, I recommend buying new ones. When choosing screens, make sure they both have a SPI interface.