Using Teensy 4.0 with LCD Display.

schlank

Active member
Hello!

I am using this TFT display with a Teensy 4.0:

https://www.amazon.de/gp/product/B07DK3RXCR/

To make things easy I am using a Arudino/Teensy shield and then the LCD is being stacked on top.

This works fine BUT I have a question:

As the Pins on the teensy are not 5V tolerant I wonder if this stacking solution is any good for long term operation as maybe one pin from the display is using maybe an 5V output that potentially could harm the Teensy?

Is this something I need to take care of?


Have a nice day!
 
I have that identical display. My solution was to remove that 3.3v regulator, then connect the 5v pin from the now removed regulator pad directly to the right-hand side of R1. Thus the pin labelled 5V becomes 3.3v.
 
How do you plan on driving an 8 bit parallel display on a Teeny 4.0?
You can do it on a 4.1/ Teensy Micromod with hardware support, but not on a 4.0
 
Hi!

ChatGTP provided me some (working) code that uses MCUFRIEND_kbv.h and starts with:

Code:
#define LCD_CS A3
#define LCD_CD A2
#define LCD_WR A1
#define LCD_RD A0
#define LCD_RESET A4

void setup() {
  uint16_t identifier = tft.readID();
  tft.begin(identifier);
...
}

So I dont know which kind of communication is used in the background? Is it SPI?

Thanks for clearing things out.
 
Yeah, it's using DIgital pins 0-8 probably as it would from an Arduino UNO, and then A0-A4 for control lines.
While this will work, it's not an efficient solution at all especially for the Teensy.

It all comes down to what you are doing with the display. Do you need fast updates?Do you need the Teensy to do other things while updating the display (eg non blocking transfers)
If the answer is no, you can keep using MCUFRIEND library. If you need any the above, you can check out my two libraries (https://github.com/david-res) for the Teensy 4.1 and Teensy Micromod for a much faster/stable interface, and non blocking transfers (for the MicroMod only).

You can also use SPI displays like the HX8357 breakout from Adafruit, although the update rate will be slower, but fewer pins are required.
 
Hi!
Thanks for providing your libraries but I want to use Teensy 4.0 not micromod or 4.1.
Are there any other SPI libraries that work on teensy 4.0?

Indeed I think it is not the best practice to use so many I/O lines.

Edit: I tried to use the TFT_eSPI library but the SPI connection is not working properly.
In a test sketch the teensy could not read any regsiters.
 
Ah yes maybe not. The SPI Lines on the display PCB may only are connected to the SD-Card reader. So what are the pros of SPI connection?
 
Your current display is 8 bit parallel only. The SPI lines are for the SD card slot.

In theory, 8 bit parallel vs SPI at the same bus speed - SPI will be slower. But again, it all comes down to what you need in terms of performance.

If you want to use an SPI display, purchase one on AliExpress, just search for ILI9488 SPI and you'll find many options.
For an SPI library, you have ILI9488_t3 by mjs513 & KurtE
 
Back
Top