ST7735_TFT_PICO

Table of contents

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

Overview

• Name: ST7735_TFT_PICO
• Description:

0. Library for a TFT SPI LCD, ST7735 Driver
1. Raspberry pi PICO RP2040 library.
2. Inverse colour, rotate, sleep, idle & vertical scroll 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
• Port of my Raspberry PI library version 1.5 at github link.
• Developed on Toolchain:
  1. Raspberry pi PICO RP2040
  2. SDK(1.4.0) C++
  3. compiler G++ for arm-none-eabi((15:10.3-2021.07-4)
  4. CMAKE(VERSION 3.12) , VScode(1.84.2)
  5. Linux Mint 21.2

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
ST7735_TFT_HELLO	Hello world	---
ST7735_TFT_TESTS	Text + fonts	---
ST7735_TFT_GRAPHICS	Graphics	---
ST7735_TFT_FUNCTIONS_FPS	Functions(like rotate scroll) + FPS test 702	---
ST7735_TFT_BMP_DATA	bi colour, 24 & 16 bitmaps tests + FPS test 701	Bitmap data is stored in arrays on PICO

Software

API

The API (application programming interface) documentation is at link hosted on github pages and generated by Doxygen.

URL API Link

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
3. USER OPTION 3 PCB_TYPE

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. "nd 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.

USER OPTION 3 PCB Version

Select your PCB controller type by passing an enum type to function TFTInitPCBType. Default is "TFT_ST7735R_Red". If you select the wrong one if may still work but with inverted colors.

Number	Description	Enum label	Tested on
1	ST7735B controller	TFT_ST7735B	n/a
2	ST7735R "Green Tab"	TFT_ST7735R_Green	n/a
3	ST7735R "Red Tab"	TFT_ST7735R_Red	RED PCB v1.1, 1.44 , 128 x 128 pixels
4	ST7735S "Black Tab"	TFT_ST7735S_Black	RED PCB v1.2, 1.8 , 128 x 160 pixels

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 ST7735_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 a number in event of an error, such as wrong font chosen , ASCII character outside chosen fonts range, character out of screen bounds and invalid character array pointer object. See API docs for details

Bitmap

There are 4 functions to support drawing bitmaps,

Num	Function Name	Colour support	bitmap size Max	Note
1	TFTdrawIcon	bi-colour	(8 x (0-Max_y)) 128 bytes max	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

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

These functions will return error codes in event of an error, see API docs for details.

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 150R/220R ohm 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

Output of some of the test routine's. Left to right

1. Bitmap (bi-color) A background and a foreground, 128 X 128 pixels.
2. Different sizes of default font. Size 2 3 4 & 5 shown.
3. Different Fonts at font size 2, fonts 1-6 All these fonts are scale-able
4. Graphics.
5. Clock Demo Test 11, showing icons, and font 7 "BigNums"
6. 24 bit RGB test image displayed from a data array , 128 X 128 pixels.
7. 16 bit 565 test image displayed from a data array , 128 X 128 pixels.
8. Fonts 7-12