ST7789_TFT_PICO

Table of contents

• Overview
• Test
• Software
  • User Options
  • Fonts
  • Bitmap
• Hardware
• Output

Overview

• Name: ST7789_TFT_PICO
• Description:

0. Library for a TFT SPI LCD, ST7789 Driver
1. Raspberry pi PICO RP2040 library.
2. Inverse colour, rotate, sleep modes supported.
3. 12 fonts included.
4. Graphics + print class included.
5. bi-color, 16 bit and 24 colour Bitmaps supported.
6. Hardware and software SPI

• Author: Gavin Lyons
• Developed on Toolchain:
  1. Raspberry pi PICO RP2040
  2. SDK(2.1.0) C++
  3. compiler G++ for arm-none-eabi(13.2.1)
  4. CMAKE(VERSION 3.18) , VScode(1.95.3)
  5. Linux Mint 22.1

Test

There are example files included. User picks the one they want by editing the CMakeLists.txt :: add_executable(${PROJECT_NAME} section. Comment in one path and one path only.

Filename	Function	Note
ST7789_TFT_HELLO	Hello world	---
ST7789_TFT_TEXT	Text + fonts	---
ST7789_TFT_GRAPHICS	Graphics	---
ST7789_TFT_FUNCTIONS_FPS	Functions(like rotate scroll) + FPS test	---
ST7789_TFT_BMP_DATA	1, 16 & 24 bit colour bitmaps tests + FPS test	Bitmap data is stored in arrays on PICO

Software

User Options

In the main.cpp example files. There are four sections in "Setup()" function where user can make adjustments to select for SPI type used, PCB type used and screen size.

0. USER OPTION 0 SPI_SPEED + TYPE
1. USER OPTION 1 GPIO
2. USER OPTION 2 SCREEN SECTION

USER OPTION 0 SPI SPEED

Here the user can pass the SPI Bus freq in kiloHertz, Currently set to 8 Mhz. Max SPI speed on the PICO is 62.5Mhz. There is a file with SPI test results for the FPS tests in extra/doc folder. 2nd parameter is the SPI interface(spi0 spi1 etc).

If users wants software SPI just call this method with just one argument for the optional GPIO software uS delay, which by default is zero. Setting this higher can be used to slow down Software SPI which may be beneficial in some setups.

USER OPTION 1 GPIO

The 5 GPIO pins used, the clock and data lines must be the clock and data lines of spi interface chosen in option 0 if using hardware SPI.

USER OPTION 2 Screen size + Offsets

In the main.cpp file, in USER OPTION 2 . User can adjust screen pixel height, screen pixel width and x & y screen offsets. These offsets can be used in the event of screen damage or manufacturing errors around edge such as cropped data or defective pixels. The function TFTInitScreenSize sets them.

Fonts

Font data table:

num	enum name	Char size XbyY	ASCII range	Size bytes	Size Scale-able
1	$_Default	5x8	0-0xFF, Full Extended	1275	Y
2	$_Thick	7x8	0x20-0x5A, no lowercase letters	406	Y
3	$_SevenSeg	4x8	0x20-0x7A	360	Y
4	$_Wide	8x8	0x20-0x5A, no lowercase letters	464	Y
5	$_Tiny	3x8	0x20-0x7E	285	Y
6	$_Homespun	7x8	0x20-0x7E	658	Y
7	$_Bignum	16x32	0x2D-0x3A ,0-10 - . / :	896	N
8	$_Mednum	16x16	0x2D-0x3A ,0-10 - . / :	448	N
9	$_ArialRound	16x24	0x20-0x7E	4608	N
10	$_ArialBold	16x16	0x20-0x7E	3072	N
11	$_Mia	8x16	0x20-0x7E	1520	N
12	$_Dedica	6x12	0x20-0x7E	1152	N

1. $ = TFTFont
2. A print class is available to print out many data types.
3. Fonts 1-6 are byte high(at text size 1) scale-able fonts, columns of padding added by SW.
4. Font 7-8 are large numerical fonts and cannot be scaled(just one size).
5. Fonts 9-12 Alphanumeric fonts and cannot be scaled(just one size) These fonts are optional and can be removed from program by commenting out the relevant TFT_OPTIONAL_FONT_X define in the ST7789_TFT_Font.hpp file

Font Methods:

Font num	Method	Size parameter	Notes
1-6	drawChar	Y	draws single character
1-6	drawText	Y	draws character array
7-12	drawChar	N	draws single character
7-12	drawText	N	draws character array
1-12	print	~	Polymorphic print class which will print out many data types

These functions return an error code in event of an error.

Bitmap

Functions to support drawing bitmaps,

Num	Function Name	Colour support	test bitmap data size	Note
1	TFTdrawIcon	bi-colour	(8 x (0-Max_y))	Data vertically addressed
2	TFTdrawBitmap	bi-colour	2048 bytes	Data horizontally addressed
3	TFTdrawBitmap16Data	16 bit color 565	32768	Data from array on PICO
4	TFTdrawBitmap24Data	24 bit color	49152	Data from array on PICO, Converted by software to 16-bit color
5	TFTdrawSpriteData	16 bit color 565	32768	Data from array on PICO, Draws background color transparent

1. Bitmap size in kiloBytes = (screenWidth * screenHeight * bitsPerPixel)/(1024 * 8)
2. Math in bitmap size column 2-5 assumes 128x128 bitmap.
3. The data array for 1 and 2 is created from image files using file data conversion tool link
4. The data array for 3 and 5 is created from BMP files using file data conversion tool link

These functions will return an error code in event of an error.

Hardware

Connections as setup in main.cpp test file.

TFT PinNum	Pindesc	HW SPI
1	LED	VCC
2	SCLK	GPIO18
3	SDA	GPIO19
4	A0/DC	GPIO3
5	RESET	GPIO17
6	SS/CS	GPIO2
7	GND	GND
8	VCC	VCC

1. NOTE connect LED backlight pin 1 thru a resistor to 3.3/5V VCC.
2. This is a 3.3V logic device do NOT connect the I/O logic lines to 5V logic device.
3. You can connect VCC to 5V if there is a 3.3 volt regulator on back of TFT module.
4. SW SPI pick any GPIO you like , HW SPI SCLK and SDA will be tied to spio interface.
5. Backlight on/off control is left to user.

Output