I2C Interface With S2 Mini - DONE.LAND

The I2C Interface is a commonly used two-wire-interface to connect external devices like small displays or sensors to a microcontroller.

Connecting external devices to S2 Mini via I2C is trivial and requires next to no setup. Just connect the device to power, and connect the two I2C wires to the corresponding GPIOs on the S2 Mini.

Below I am demonstrating how to connect an OLED display via I2C to S2 Mini.

Wiring

This is the wiring for the four pins of the OLED display:

OLED Display	S2 Mini	Description
GND	GND	Ground
VDD	3V3	3.3V
SCK/SCL	35	I2C SCL
SDA	33	I2C SDA

To connect other/additional I2C devices to the S2 Mini, connect them all to pins 33 (SDA) and 35 (SCL).

The S2 Mini can use any pin to communicate with I2C devices. By default, it uses the pins 33 and 35. To use different pins, you need to define these in the device initializers of your code.

Library

To drive a simple 0.96” OLED display, the library ESP8266 and ESP32 OLED driver for SSD1306 displays from ThingPulse was used.

I uploaded and ran the default example code which draws various examples onto the OLED display.

The default device initializer and the default I2C address (0x3c) worked out-of-the-box for the 128x64 pixel display I used:

SSD1306Wire display(0x3c, SDA, SCL, GEOMETRY_128_64);

Adjust the line to support different geometries (i.e. 128x32) or to use different I2C pins.

OLED displays typically use the I2C device addresses 0x3c or 0x3d. If the display stays blank with 0x3c, replace it with 0x3d and try again.

The common pin labels SDA and SCL can only be used after you tweaked the pins_arduino.h file (as described in the previous article). Else, these constants are undefined. You can also replace SDA with 33, and SCL with 35.

Here is the example code I have taken from the library examples:

/**
   The MIT License (MIT)

   Copyright (c) 2018 by ThingPulse, Daniel Eichhorn
   Copyright (c) 2018 by Fabrice Weinberg

   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
   in the Software without restriction, including without limitation the rights
   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   copies of the Software, and to permit persons to whom the Software is
   furnished to do so, subject to the following conditions:

   The above copyright notice and this permission notice shall be included in all
   copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   SOFTWARE.

   ThingPulse invests considerable time and money to develop these open source libraries.
   Please support us by buying our products (and not the clones) from
   https://thingpulse.com

*/

// Include the correct display library

// For a connection via I2C using the Arduino Wire include:
#include <Arduino.h>
#include <Wire.h>               // Only needed for Arduino 1.6.5 and earlier
#include "SSD1306Wire.h"        // legacy: #include "SSD1306.h"
// OR #include "SH1106Wire.h"   // legacy: #include "SH1106.h"

// For a connection via I2C using brzo_i2c (must be installed) include:
// #include <brzo_i2c.h>        // Only needed for Arduino 1.6.5 and earlier
// #include "SSD1306Brzo.h"
// OR #include "SH1106Brzo.h"

// For a connection via SPI include:
// #include <SPI.h>             // Only needed for Arduino 1.6.5 and earlier
// #include "SSD1306Spi.h"
// OR #include "SH1106SPi.h"


// Optionally include custom images
#include "images.h"


// Initialize the OLED display using Arduino Wire:
//SSD1306Wire display(0x3c, SDA, SCL);   // ADDRESS, SDA, SCL  -  SDA and SCL usually populate automatically based on your board's pins_arduino.h e.g. https://github.com/esp8266/Arduino/blob/master/variants/nodemcu/pins_arduino.h
// SSD1306Wire display(0x3c, D3, D5);  // ADDRESS, SDA, SCL  -  If not, they can be specified manually.
SSD1306Wire display(0x3c, SDA, SCL, GEOMETRY_128_64);  // ADDRESS, SDA, SCL, OLEDDISPLAY_GEOMETRY  -  Extra param required for 128x32 displays.
// SH1106Wire display(0x3c, SDA, SCL);     // ADDRESS, SDA, SCL

// Initialize the OLED display using brzo_i2c:
// SSD1306Brzo display(0x3c, D3, D5);  // ADDRESS, SDA, SCL
// or
// SH1106Brzo display(0x3c, D3, D5);   // ADDRESS, SDA, SCL

// Initialize the OLED display using SPI:
// D5 -> CLK
// D7 -> MOSI (DOUT)
// D0 -> RES
// D2 -> DC
// D8 -> CS
// SSD1306Spi display(D0, D2, D8);  // RES, DC, CS
// or
// SH1106Spi display(D0, D2);       // RES, DC


#define DEMO_DURATION 3000
typedef void (*Demo)(void);

int demoMode = 0;
int counter = 1;

void setup() {
  Serial.begin(115200);
  Serial.println();
  Serial.println();


  // Initialising the UI will init the display too.
  display.init();

  display.flipScreenVertically();
  display.setFont(ArialMT_Plain_10);

}

void drawFontFaceDemo() {
  // Font Demo1
  // create more fonts at http://oleddisplay.squix.ch/
  display.setTextAlignment(TEXT_ALIGN_LEFT);
  display.setFont(ArialMT_Plain_10);
  display.drawString(0, 0, "Hello world");
  display.setFont(ArialMT_Plain_16);
  display.drawString(0, 10, "Hello world");
  display.setFont(ArialMT_Plain_24);
  display.drawString(0, 26, "Hello world");
}

void drawTextFlowDemo() {
  display.setFont(ArialMT_Plain_10);
  display.setTextAlignment(TEXT_ALIGN_LEFT);
  display.drawStringMaxWidth(0, 0, 128,
                             "Lorem ipsum\n dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore." );
}

void drawTextAlignmentDemo() {
  // Text alignment demo
  display.setFont(ArialMT_Plain_10);

  // The coordinates define the left starting point of the text
  display.setTextAlignment(TEXT_ALIGN_LEFT);
  display.drawString(0, 10, "Left aligned (0,10)");

  // The coordinates define the center of the text
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 22, "Center aligned (64,22)");

  // The coordinates define the right end of the text
  display.setTextAlignment(TEXT_ALIGN_RIGHT);
  display.drawString(128, 33, "Right aligned (128,33)");
}

void drawRectDemo() {
  // Draw a pixel at given position
  for (int i = 0; i < 10; i++) {
    display.setPixel(i, i);
    display.setPixel(10 - i, i);
  }
  display.drawRect(12, 12, 20, 20);

  // Fill the rectangle
  display.fillRect(14, 14, 17, 17);

  // Draw a line horizontally
  display.drawHorizontalLine(0, 40, 20);

  // Draw a line horizontally
  display.drawVerticalLine(40, 0, 20);
}

void drawCircleDemo() {
  for (int i = 1; i < 8; i++) {
    display.setColor(WHITE);
    display.drawCircle(32, 32, i * 3);
    if (i % 2 == 0) {
      display.setColor(BLACK);
    }
    display.fillCircle(96, 32, 32 - i * 3);
  }
}

void drawProgressBarDemo() {
  int progress = (counter / 5) % 100;
  // draw the progress bar
  display.drawProgressBar(0, 32, 120, 10, progress);

  // draw the percentage as String
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 15, String(progress) + "%");
}

void drawImageDemo() {
  // see http://blog.squix.org/2015/05/esp8266-nodemcu-how-to-create-xbm.html
  // on how to create xbm files
  display.drawXbm(34, 14, WiFi_Logo_width, WiFi_Logo_height, WiFi_Logo_bits);
}

Demo demos[] = {drawFontFaceDemo, drawTextFlowDemo, drawTextAlignmentDemo, drawRectDemo, drawCircleDemo, drawProgressBarDemo, drawImageDemo};
int demoLength = (sizeof(demos) / sizeof(Demo));
long timeSinceLastModeSwitch = 0;

void loop() {
  // clear the display
  display.clear();
  // draw the current demo method
  demos[demoMode](i2cinterface/);

  display.setFont(ArialMT_Plain_10);
  display.setTextAlignment(TEXT_ALIGN_RIGHT);
  display.drawString(128, 54, String(millis()));
  // write the buffer to the display
  display.display();

  if (millis() - timeSinceLastModeSwitch > DEMO_DURATION) {
    demoMode = (demoMode + 1)  % demoLength;
    timeSinceLastModeSwitch = millis();
  }
  counter++;
  delay(10);
}

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