資料來源：
1.https://youyouyou.pixnet.net/blog/post/121069748-esp32-x-nbiot-%e8%bc%94%e5%8a%a9%e7%89%88-%e8%83%8c%e9%9d%a2i2c-lcd?pixfrom=related
本文實作尤老師製作的「ESP32輔助板」背面 I2C 使用方法，背面的I2C為附加的PCF85741 I2C晶片，因此使用的腳位是 26 ,27 而非 21 , 22。
要使用ESP32輔助板背面的 I2C 介面，必須將 SDA 設為 GPIO 26，SCL 設為 GPIO 27。每個 I2C 裝置都會有一個位址，宣告錯誤的位址是不會有任何反應的，所以必須先做一次 I2C 掃描，取得正確位置。
我們可以使用下面程式碼掃描 I2C 的位址：
#include <Wire.h>
void setup()
{
Serial.begin (115200);
Wire.begin (26, 27); // sda=GPIO_26, scl=GPIO_27
}
void Scanner ()
{
Serial.println ();
Serial.println ("I2C scanner. Scanning ...");
byte count = 0;
Wire.begin();
for (byte i = 8; i < 120; i++)
{
Wire.beginTransmission (i); // Begin I2C transmission Address (i)
if (Wire.endTransmission () == 0) //0=success(ACK response)
{
Serial.print ("Found address: ");
Serial.print (i, DEC);
Serial.print (" (0x");
Serial.print (i, HEX); // PCF8574 7 bit address
Serial.println (")");
count++;
}
}
Serial.print ("Found ");
Serial.print (count, DEC); // numbers of devices
Serial.println (" device(s).");
}
void loop()
{
Scanner ();
delay (5000);
}我接上一個 0.96吋的 OLED 螢幕，掃描到的 I2C 的位置有3個，分別是
I2C scanner. Scanning …
I2C 位址掃描結果 用 Arduino 打開 AdafruitSSD1306 範例檔，我參考網路上資源加上了一些文字顯示，程式碼如下：
/**************************************************************************
This is an example for our Monochrome OLEDs based on SSD1306 drivers
Pick one up today in the adafruit shop!
------> http://www.adafruit.com/category/63_98
This example is for a 128x64 pixel display using I2C to communicate
3 pins are required to interface (two I2C and one reset).
Adafruit invests time and resources providing this open
source code, please support Adafruit and open-source
hardware by purchasing products from Adafruit!
Written by Limor Fried/Ladyada for Adafruit Industries,
with contributions from the open source community.
BSD license, check license.txt for more information
All text above, and the splash screen below must be
included in any redistribution.
**************************************************************************/
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
// The pins for I2C are defined by the Wire-library.
// On an arduino UNO: A4(SDA), A5(SCL)
// On an arduino MEGA 2560: 20(SDA), 21(SCL)
// On an arduino LEONARDO: 2(SDA), 3(SCL), ...
#define OLED_RESET 4 // Reset pin # (or -1 if sharing Arduino reset pin)
#define SCREEN_ADDRESS 0x3C ///這裡要設定Address為 0x3C
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
#define NUMFLAKES 10 // Number of snowflakes in the animation example
#define LOGO_HEIGHT 16
#define LOGO_WIDTH 16
static const unsigned char PROGMEM logo_bmp[] =
{ 0b00000000, 0b11000000,
0b00000001, 0b11000000,
0b00000001, 0b11000000,
0b00000011, 0b11100000,
0b11110011, 0b11100000,
0b11111110, 0b11111000,
0b01111110, 0b11111111,
0b00110011, 0b10011111,
0b00011111, 0b11111100,
0b00001101, 0b01110000,
0b00011011, 0b10100000,
0b00111111, 0b11100000,
0b00111111, 0b11110000,
0b01111100, 0b11110000,
0b01110000, 0b01110000,
0b00000000, 0b00110000 };
void setup() {
Serial.begin (115200);
Wire.begin (26, 27); // sda=GPIO_26, scl=GPIO_27，設I2C腳位為26,27
// SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
if(!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
Serial.println(F("SSD1306 allocation failed"));
for(;;); // Don't proceed, loop forever
}
// Show initial display buffer contents on the screen --
// the library initializes this with an Adafruit splash screen.
display.display();
delay(2000); // Pause for 2 seconds
// Clear the buffer
display.clearDisplay();
// Draw a single pixel in white
display.drawPixel(10, 10, SSD1306_WHITE);
// Show the display buffer on the screen. You MUST call display() after
// drawing commands to make them visible on screen!
display.display();
delay(2000);
// display.display() is NOT necessary after every single drawing command,
// unless that's what you want...rather, you can batch up a bunch of
// drawing operations and then update the screen all at once by calling
// display.display(). These examples demonstrate both approaches...
testdrawline(); // Draw many lines
testdrawrect(); // Draw rectangles (outlines)
testfillrect(); // Draw rectangles (filled)
testdrawcircle(); // Draw circles (outlines)
testfillcircle(); // Draw circles (filled)
testdrawroundrect(); // Draw rounded rectangles (outlines)
testfillroundrect(); // Draw rounded rectangles (filled)
testdrawtriangle(); // Draw triangles (outlines)
testfilltriangle(); // Draw triangles (filled)
testdrawchar(); // Draw characters of the default font
testdrawstyles(); // Draw 'stylized' characters
testscrolltext(); // Draw scrolling text
testdrawbitmap(); // Draw a small bitmap image
// Invert and restore display, pausing in-between
display.invertDisplay(true);
delay(1000);
display.invertDisplay(false);
delay(1000);
testanimate(logo_bmp, LOGO_WIDTH, LOGO_HEIGHT); // Animate bitmaps
}
void loop() {
display.setTextColor(WHITE); //設定顯示文字的顏色
display.setTextSize(1); //設定第1行文字的大小為1
display.setCursor(0,0); //設定第1行文字在oled上顯示的座標
display.println("Hello, world!"); //設定第1行顯示的文字
display.setTextSize(2); //設定第2行文字的大小為2
display.setCursor(0,15); //設定第2行文字在oled上顯示的座標
display.println("First"); //設定第2行顯示的文字
display.setTextSize(3); //設定第3行文字的大小為3
display.setCursor(0,40); //設定第3行文字在oled上顯示的座標
display.println("Second"); //設定第3行顯示的文字
display.display(); //顯示資料緩衝區內的資料
delay(2000);
display.clearDisplay(); //清除資料緩衝區內的資料
}
void testdrawline() {
int16_t i;
display.clearDisplay(); // Clear display buffer
for(i=0; i<display.width(); i+=4) {
display.drawLine(0, 0, i, display.height()-1, SSD1306_WHITE);
display.display(); // Update screen with each newly-drawn line
delay(1);
}
for(i=0; i<display.height(); i+=4) {
display.drawLine(0, 0, display.width()-1, i, SSD1306_WHITE);
display.display();
delay(1);
}
delay(250);
display.clearDisplay();
for(i=0; i<display.width(); i+=4) {
display.drawLine(0, display.height()-1, i, 0, SSD1306_WHITE);
display.display();
delay(1);
}
for(i=display.height()-1; i>=0; i-=4) {
display.drawLine(0, display.height()-1, display.width()-1, i, SSD1306_WHITE);
display.display();
delay(1);
}
delay(250);
display.clearDisplay();
for(i=display.width()-1; i>=0; i-=4) {
display.drawLine(display.width()-1, display.height()-1, i, 0, SSD1306_WHITE);
display.display();
delay(1);
}
for(i=display.height()-1; i>=0; i-=4) {
display.drawLine(display.width()-1, display.height()-1, 0, i, SSD1306_WHITE);
display.display();
delay(1);
}
delay(250);
display.clearDisplay();
for(i=0; i<display.height(); i+=4) {
display.drawLine(display.width()-1, 0, 0, i, SSD1306_WHITE);
display.display();
delay(1);
}
for(i=0; i<display.width(); i+=4) {
display.drawLine(display.width()-1, 0, i, display.height()-1, SSD1306_WHITE);
display.display();
delay(1);
}
delay(2000); // Pause for 2 seconds
}
void testdrawrect(void) {
display.clearDisplay();
for(int16_t i=0; i<display.height()/2; i+=2) {
display.drawRect(i, i, display.width()-2*i, display.height()-2*i, SSD1306_WHITE);
display.display(); // Update screen with each newly-drawn rectangle
delay(1);
}
delay(2000);
}
void testfillrect(void) {
display.clearDisplay();
for(int16_t i=0; i<display.height()/2; i+=3) {
// The INVERSE color is used so rectangles alternate white/black
display.fillRect(i, i, display.width()-i*2, display.height()-i*2, SSD1306_INVERSE);
display.display(); // Update screen with each newly-drawn rectangle
delay(1);
}
delay(2000);
}
void testdrawcircle(void) {
display.clearDisplay();
for(int16_t i=0; i<max(display.width(),display.height())/2; i+=2) {
display.drawCircle(display.width()/2, display.height()/2, i, SSD1306_WHITE);
display.display();
delay(1);
}
delay(2000);
}
void testfillcircle(void) {
display.clearDisplay();
for(int16_t i=max(display.width(),display.height())/2; i>0; i-=3) {
// The INVERSE color is used so circles alternate white/black
display.fillCircle(display.width() / 2, display.height() / 2, i, SSD1306_INVERSE);
display.display(); // Update screen with each newly-drawn circle
delay(1);
}
delay(2000);
}
void testdrawroundrect(void) {
display.clearDisplay();
for(int16_t i=0; i<display.height()/2-2; i+=2) {
display.drawRoundRect(i, i, display.width()-2*i, display.height()-2*i,
display.height()/4, SSD1306_WHITE);
display.display();
delay(1);
}
delay(2000);
}
void testfillroundrect(void) {
display.clearDisplay();
for(int16_t i=0; i<display.height()/2-2; i+=2) {
// The INVERSE color is used so round-rects alternate white/black
display.fillRoundRect(i, i, display.width()-2*i, display.height()-2*i,
display.height()/4, SSD1306_INVERSE);
display.display();
delay(1);
}
delay(2000);
}
void testdrawtriangle(void) {
display.clearDisplay();
for(int16_t i=0; i<max(display.width(),display.height())/2; i+=5) {
display.drawTriangle(
display.width()/2 , display.height()/2-i,
display.width()/2-i, display.height()/2+i,
display.width()/2+i, display.height()/2+i, SSD1306_WHITE);
display.display();
delay(1);
}
delay(2000);
}
void testfilltriangle(void) {
display.clearDisplay();
for(int16_t i=max(display.width(),display.height())/2; i>0; i-=5) {
// The INVERSE color is used so triangles alternate white/black
display.fillTriangle(
display.width()/2 , display.height()/2-i,
display.width()/2-i, display.height()/2+i,
display.width()/2+i, display.height()/2+i, SSD1306_INVERSE);
display.display();
delay(1);
}
delay(2000);
}
void testdrawchar(void) {
display.clearDisplay();
display.setTextSize(1); // Normal 1:1 pixel scale
display.setTextColor(SSD1306_WHITE); // Draw white text
display.setCursor(0, 0); // Start at top-left corner
display.cp437(true); // Use full 256 char 'Code Page 437' font
// Not all the characters will fit on the display. This is normal.
// Library will draw what it can and the rest will be clipped.
for(int16_t i=0; i<256; i++) {
if(i == '\n') display.write(' ');
else display.write(i);
}
display.display();
delay(2000);
}
void testdrawstyles(void) {
display.clearDisplay();
display.setTextSize(1); // Normal 1:1 pixel scale
display.setTextColor(SSD1306_WHITE); // Draw white text
display.setCursor(0,0); // Start at top-left corner
display.println(F("Hello, world!"));
display.setTextColor(SSD1306_BLACK, SSD1306_WHITE); // Draw 'inverse' text
display.println(3.141592);
display.setTextSize(2); // Draw 2X-scale text
display.setTextColor(SSD1306_WHITE);
display.print(F("0x")); display.println(0xDEADBEEF, HEX);
display.display();
delay(2000);
}
void testscrolltext(void) {
display.clearDisplay();
display.setTextSize(2); // Draw 2X-scale text
display.setTextColor(SSD1306_WHITE);
display.setCursor(10, 0);
display.println(F("scroll"));
display.display(); // Show initial text
delay(100);
// Scroll in various directions, pausing in-between:
display.startscrollright(0x00, 0x0F);
delay(2000);
display.stopscroll();
delay(1000);
display.startscrollleft(0x00, 0x0F);
delay(2000);
display.stopscroll();
delay(1000);
display.startscrolldiagright(0x00, 0x07);
delay(2000);
display.startscrolldiagleft(0x00, 0x07);
delay(2000);
display.stopscroll();
delay(1000);
}
void testdrawbitmap(void) {
display.clearDisplay();
display.drawBitmap(
(display.width() - LOGO_WIDTH ) / 2,
(display.height() - LOGO_HEIGHT) / 2,
logo_bmp, LOGO_WIDTH, LOGO_HEIGHT, 1);
display.display();
delay(1000);
}
#define XPOS 0 // Indexes into the 'icons' array in function below
#define YPOS 1
#define DELTAY 2
void testanimate(const uint8_t *bitmap, uint8_t w, uint8_t h) {
int8_t f, icons[NUMFLAKES][3];
// Initialize 'snowflake' positions
for(f=0; f< NUMFLAKES; f++) {
icons[f][XPOS] = random(1 - LOGO_WIDTH, display.width());
icons[f][YPOS] = -LOGO_HEIGHT;
icons[f][DELTAY] = random(1, 6);
Serial.print(F("x: "));
Serial.print(icons[f][XPOS], DEC);
Serial.print(F(" y: "));
Serial.print(icons[f][YPOS], DEC);
Serial.print(F(" dy: "));
Serial.println(icons[f][DELTAY], DEC);
}
for(;;) { // Loop forever...
display.clearDisplay(); // Clear the display buffer
// Draw each snowflake:
for(f=0; f< NUMFLAKES; f++) {
display.drawBitmap(icons[f][XPOS], icons[f][YPOS], bitmap, w, h, SSD1306_WHITE);
}
display.display(); // Show the display buffer on the screen
delay(200); // Pause for 1/10 second
// Then update coordinates of each flake...
for(f=0; f< NUMFLAKES; f++) {
icons[f][YPOS] += icons[f][DELTAY];
// If snowflake is off the bottom of the screen...
if (icons[f][YPOS] >= display.height()) {
// Reinitialize to a random position, just off the top
icons[f][XPOS] = random(1 - LOGO_WIDTH, display.width());
icons[f][YPOS] = -LOGO_HEIGHT;
icons[f][DELTAY] = random(1, 6);
}
}
}
}OLED顯示影片如下：https://www.youtube.com/watch?v=9GmNvnwMRaI
如果使用的OLED是 128×64，無法正常顯示的話，需要修改 Arduino下 Libraries 資料夾中Adafruit_SSD1306的 Adafruit_SSD1306.h，修改為 #define SSD1306_128_64
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