I2C (Inter-Integrated Circuit)#

Discover the I2C communication protocol and learn how to communicate with I2C devices using the PULSAR C6 board. This section will cover I2C bus setup and communication with I2C peripherals.

I2C Overview#

I2C (Inter-Integrated Circuit) is a synchronous, multi-master, multi-slave, packet-switched, single-ended, serial communication bus. It is commonly used to connect low-speed peripherals to processors and microcontrollers. The PULSAR C6 development board features I2C communication capabilities, allowing you to interface with a wide range of I2C devices.

Pinout Details#

Below is the pinout table for the I2C connections on the PULSAR C6, detailing the pin assignments for SDA and SCL.

Table 9 QWIIC-Compatible JST Connector#
Pin	JST Function	Arduino Compatibility	ESP32-S3 GPIO	GPIO Function
1	GND	GND	GND	GND
2	3.3V	3.3V	3.3V	3.3V
3	SDA / MUX IO	A4	GPIO5	RTC_GPIO5, GPIO5, TOUCH5, ADC1_CH4
4	SCL / MUX IO	A5	GPIO6	RTC_GPIO6, GPIO6, TOUCH6, ADC1_CH5

Scanning for I2C Devices#

To scan for I2C devices connected to the bus, you can use the following code snippet:

import machine

i2c = machine.I2C(0, scl=machine.Pin(6), sda=machine.Pin(5))
devices = i2c.scan()

for device in devices:
    print("Device found at address: {}".format(hex(device)))

#include <Wire.h>

void setup() {
  // in setup
  Wire.setSDA(5);
  Wire.setSCL(6);
  Wire.begin();
  Serial.begin(9600); // Start serial communication at 9600 baud rate
  while (!Serial); // Wait for serial port to connect
  Serial.println("\nI2C Scanner");
}

void loop() {
  byte error, address;
  int nDevices;

  Serial.println("Scanning...");

  nDevices = 0;
  for(address = 1; address < 127; address++ ) {
    // The i2c_scanner uses the return value of the Write.endTransmisstion to see if
    // a device did acknowledge to the address.
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0) {
      Serial.print("I2C device found at address 0x");
      if (address<16)
        Serial.print("0");
      Serial.print(address, HEX);
      Serial.println("  !");

      nDevices++;
    }
    else if (error==4) {
      Serial.print("Unknown error at address 0x");
      if (address<16)
        Serial.print("0");
      Serial.println(address, HEX);
    }
  }
  if (nDevices == 0)
    Serial.println("No I2C devices found\n");
  else
    Serial.println("done\n");

  delay(5000);           // wait 5 seconds for next scan
}

SSD1306 Display#

The display 128x64 pixel monochrome OLED display equipped with an SSD1306 controller is connected using a JST 1.25mm 4-pin connector. The following table provides the pinout details for the display connection.

Table 10 SSD1306 Display Pinout#
Pin	Connection
1	GND
2	VCC
3	SDA
4	SCL

Library Support#

The ocks.py library for MicroPython on ESP32 & RP2040 is compatible with the SSD1306 display controller.

Installation

Open Thonny.
Navigate to Tools -> Manage Packages.
Search for ocks and click Install.

Alternatively, download the library from ocks.py.

Microcontroller Configuration

SoftI2C(scl, sda, *, freq=400000, timeout=50000)

Change the following line depending on your microcontroller:

For ESP32:

>>> i2c = machine.SoftI2C(freq=400000, timeout=50000, sda=machine.Pin(21), scl=machine.Pin(22))

For RP2040:

>>> i2c = machine.SoftI2C(freq=400000, timeout=50000, sda=machine.Pin(4), scl=machine.Pin(5))

Example Code

import machine
from ocks import SSD1306_I2C

i2c = machine.SoftI2C(freq=400000, timeout=50000, sda=machine.Pin(*), scl=machine.Pin(*))

oled = SSD1306_I2C(128, 64, i2c)

# Fill the screen with white and display
oled.fill(1)
oled.show()

# Clear the screen (fill with black)
oled.fill(0)
oled.show()

# Display text
oled.text('UNIT', 50, 10)
oled.text('ELECTRONICS', 25, 20)
oled.show()

Replace sda=machine.Pin(*) and scl=machine.Pin(*) with the appropriate GPIO pins for your setup.

The Adafruit_SSD1306 library for Arduino is compatible with the SSD1306 display controller.