IPS display, ST7789
An IPS color TFT, 240x240, 240x320 or 135x240. It shows a negative until the driver sends INVON.
- 8 pins
- 1 setting
- In 1 project
- In 1 lesson
The IPS display, ST7789 in brief
What it is, and every setting the properties panel gives it.
The ST7789 is the controller behind the small IPS color TFTs: the square 1.3 inch 240x240 board, the 2 inch 240x320 and the 1.14 inch 135x240 on the TTGO T-Display. Its pins say SCL and SDA but it is SPI, not I2C: SCL goes to the SPI clock, pin 13 on an Uno, and SDA to MOSI on 11, with RES, DC and an optional CS on any free pins and BLK for the backlight. The modules run at 3.3 volts. The chip always has 240x320 of memory, so the 240x240 glass is its top 240 rows and a flipped rotation has to start at row 80, while the 135x240 is a window from column 52 and row 40; a driver with the wrong offset draws where nobody can see. IPS glass shows the colors inverted until the driver sends INVON, so a hand-written init without it gives a photographic negative. With CS unwired, as on the 1.3 inch board, only the reset on RES lines the bits up. Gamma, scrolling and the waits after reset are not modeled.
- Family
- Displays
- Pins
- 8
- size
- 240x240 (or 240x320, 135x240)
240x240(the default),240x320or135x240. Match it to the numbers the sketch passes toinit().
8 pins
Named as the editor names them, so a wire lands where you expect it.
How to use an ST7789 IPS TFT with an Arduino
The 1.3 inch board has no CS pin, so it listens to every clock on its wires and needs pins of its own: here SDA on A0, SCL on A1, DC on 7 and RES on 6, with BLK and VCC on 5 V. The five-argument Adafruit_ST7789 constructor runs software SPI on any pins, with -1 for the missing chip select.
Call init() with the panel’s real size and SPI_MODE3, the mode the no-CS boards are usually driven in. Wire RES: with no chip select, the reset is what lines the bits up. Set the part’s size to the numbers init() is given, or the picture lands off the glass.
#include <SPI.h>
#include <Adafruit_GFX.h>
#include <Adafruit_ST7789.h>
Adafruit_ST7789 square(-1, 7, A0, A1, 6); // no CS; DC, SDA, SCL, RES
void setup() {
square.init(240, 240, SPI_MODE3);
square.setRotation(2);
square.fillRect(0, 0, 240, 40, ST77XX_BLUE);
square.setTextColor(ST77XX_WHITE);
square.setCursor(8, 12);
square.print("ST7789 IPS");
}
void loop() {}What is true about the IPS display, ST7789, here
In its help article’s own words: what the simulation gets right, and where it stops.
Modeled
The offsets. The chip always has 240x320 of memory. The 240x240 glass is the top 240 rows of it, so a rotation that counts rows from the bottom has to start at row 80, which is the 80 in every ST7789 library. The 135x240 glass is a window from column 52 and row 40. The part stores only the glass, so a driver with the wrong offset draws where nobody can see, as it does on the bench.
The inverted glass. IPS panels show the controller's colors inverted, and every
ST7789 driver sends INVON (0x21) to put them right. Leave it out and the picture
is a photographic negative: white is black. That is modeled.
No chip select. A CS left unwired is taken as tied to ground, the way the 1.3
inch board has it. With nothing to mark where a byte starts, the hardware reset on
RES is what lines the bits up, so a driver without a reset pin has to be lucky here
as on the bench. The chip samples on the rising clock in either SPI mode, so the mode
3 that the no-CS boards are usually driven in works, and so does mode 0.
MADCTL rotation, the window, 16-bit and 18-bit pixels, sleep and display on and off behave as on the ILI9341.
Not modeled
The color order bit, 12-bit color, register reads, timing (the waits after reset
and sleep-out are not enforced), gamma, frame rate, partial mode and scrolling. The
170x320 and 240x280 panels are not in the size list.
From ST7789 IPS TFT, in full.
See the IPS display, ST7789 in a project
One built-in project uses it. It opens in the editor, already wired.
Where it turns up in a lesson
One lesson places it in its own circuit.
The boards it is shown on
This board has a built-in project with the IPS display, ST7789 in it.
Arduino libraries for the IPS display, ST7789
Built in, so the sketch compiles with nothing to install. Each page has the calls, the wiring and an example to run.
The rest of the bench
Every one of these is drawn and simulated the same way.
Wire up the IPS display, ST7789
Open the editor and push it into the breadboard. It is free, and it runs on your own machine.