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ESP8266 NodeMCU Module – I2C
The code provided demonstrates the usage of the I2C (Inter-Integrated Circuit) protocol on an ESP8266 NodeMCU module. I2C is a popular serial communication protocol used to connect multiple peripherals with a microcontroller or a microprocessor. In this context, the code initializes the I2C interface on the NodeMCU module and showcases how to read data from a specific register of an I2C device.
Pr-Request to Lean
- Embedded Protocol I2C : https://aruneworld.com/embedded/embedded-protocol/i2c/
ESP8266 I2C Core
ESP8266 hardware supports only one i2c. But in bit-banking(Bar Metal code) method you can use all your gpio pin as i2c pins. ESP8266 NodeMCU firmware platform supports only standard speed mode (Sm) 100khz . That means ESP8266 NodeMCU firmware supports 100Kbps for data transfer.
ESP8266 I2C Scanner
- Required NodeMCU Modules (Firmware) : GPIO Module, I2C Module
- Required hardware : ESP8266 with Programmer (or) NodeMCU Dev Kit
- Required software tools : ESPlorer IDE Tool
Code
This script helps identify I2C devices connected to the ESP8266 NodeMCU board by scanning through all possible device addresses and checking for responses. It’s useful for troubleshooting and verifying the connectivity of I2C devices in the system.
lua -- https://www.aruneworld.com/embedded/espressif/esp8266/esp8266_nodemcu/ -- Tested By: Arun(20170112) -- Example Name: AEW_I2C_DeviceScaner.lua ---------------------------------------- -- Setup local id = 0 -- always 0 local pinSDA = 2 -- 1~12, IO index local pinSCL = 1 -- 1~12, IO index local speed = i2c.SLOW -- only i2c.SLOW supported -- Initialize i2c.setup(id, pinSDA, pinSCL, speed) -- Initialize the I²C module. print("Scanning Started....") for count = 0, 127 do i2c.start(id) -- Send an I²C start condition. local Status = i2c.address(id, count, i2c.TRANSMITTER) -- Setup I²C address and read/write mode for the next transfer. i2c.stop(id) -- Send an I²C stop condition. if Status == true then print("Addrss - " .. count .. " Detected device address is 0x" .. string.format("%02x", count) .. " (" .. count .. ")") elseif Status == false then print("Addrss - " .. count .. " nil") end end print("Scanning End")
Explanation
This Lua script is designed to scan for I2C devices connected to an ESP8266 NodeMCU board. Here’s a breakdown of its functionality:
Setup:
- It initializes the variables
id,pinSDA,pinSCL, andspeed. idis set to 0, which typically refers to the first I2C interface on ESP8266 NodeMCU.pinSDAandpinSCLare set to the GPIO pins used for SDA (data line) and SCL (clock line), respectively.speedis set toi2c.SLOW, indicating the desired speed for I2C communication.
Initialization:
- It initializes the I2C module using
i2c.setup()with the specifiedid,pinSDA,pinSCL, andspeed.
Scanning for Devices:
- It iterates through possible device addresses from 0 to 127.
- For each address, it attempts to establish communication with the device by sending a start condition (
i2c.start()), setting the address (i2c.address()), and then stopping the communication (i2c.stop()). - If communication is successful (
Status == true), it prints the detected device address in hexadecimal and decimal format. - If communication fails (
Status == false), it prints “nil” for that address.
Printing Results:
- It prints “Scanning Started….” before starting the scanning loop.
- It prints “Scanning End” after the scanning loop is complete.
This table breaks down the code into its key components, making it easier to understand the flow and purpose of each part of the script.
| Line | Explanation |
|---|---|
| 1-4 | Introduction and setup of necessary variables and constants. |
| 6 | Initialization of the I2C module with specified parameters. |
| 8-15 | Loop to iterate through possible device addresses (0 to 127). |
| 10 | Start condition for I2C communication. |
| 11 | Attempt to set the address and read/write mode for the next transfer. |
| 12 | Stop condition for I2C communication. |
| 13-15 | Check if the status of the communication is successful and print the detected device address. |
| 17 | Print “Scanning Started….” to indicate the beginning of the scanning process. |
| 18-21 | Loop to scan through all possible device addresses and attempt communication. |
| 22-25 | Print “Scanning End” to indicate the completion of the scanning process. |
ESP8266 I2C Example
Code
id = 0
sda = 1
scl = 2
-- Initialize I2C, set pin1 as SDA, set pin2 as SCL
i2c.setup(id, sda, scl, i2c.SLOW)
-- User-defined function: Read from reg_addr content of dev_addr
function read_reg(dev_addr, reg_addr)
i2c.start(id)
i2c.address(id, dev_addr, i2c.TRANSMITTER)
i2c.write(id, reg_addr)
i2c.stop(id)
i2c.start(id)
i2c.address(id, dev_addr, i2c.RECEIVER)
c = i2c.read(id, 1)
i2c.stop(id)
return c
end
-- Get content of register 0xAA of device 0x77
reg = read_reg(0x77, 0xAA)
print(string.byte(reg))
Code Explanation
This code sets up an I2C interface, defines a function to read data from a specific register of an I2C device, and then uses this function to read the content of a specific register from a specific device address.
| Line(s) | Explanation |
|---|---|
| 1-3 | Define the I2C interface parameters: id for the I2C bus, sda for the data line, and scl for the clock line. |
| 5 | Initialize the I2C communication with the specified parameters (I2C bus, SDA pin, SCL pin, and speed). |
| 8-16 | Define a custom function read_reg to read data from a specified register address of a given device address. |
| 9-11 | Start the I2C communication and address the device in write mode to specify the register to read from. |
| 12 | Write the register address to the device. |
| 13 | Stop the I2C communication after writing the register address. |
| 14-16 | Restart the I2C communication, address the device in read mode, read one byte of data from the device, and then stop the I2C communication. |
| 17-19 | Call the read_reg function to read the content of register 0xAA from device address 0x77. |
| 20 | Print the byte value of the register content returned by the read_reg function. |
See Also
- ESP32 NodeMCU Module – I2C : https://aruneworld.com/embedded/esp32/esp32-nodemcu/esp32-nodemcu-module-i2c/
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ESP32 NodeMCU Module – I2C Interface
The ESP32 NodeMCU module supports the I2C (Inter-Integrated Circuit) communication protocol. With its built-in hardware support for I2C, the ESP32 NodeMCU module can easily interface with various I2C devices such as sensors, displays, and other peripherals. This allows for efficient data exchange between the ESP32 and I2C devices, enabling a wide range of applications in IoT, robotics, automation, and more.
Read more: ESP32 NodeMCU Module – I2C InterfacePr-Request to Lean
- Embedded Protocol I2C : https://aruneworld.com/embedded/embedded-protocol/i2c/
ESP32 NodeMCU Module I2C Functions
| Function | Description |
|---|---|
| i2c.address() | Send (SW) or queue (HWx) I²C address and read/write mode for the next transfer. |
| i2c.read() | Read (SW) or queue (HWx) data for a variable number of bytes. |
| i2c.setup() | Initialize the I²C interface for master mode. |
| i2c.start() | Send (SW) or queue (HWx) an I²C start condition. |
| i2c.stop() | Send (SW) or queue (HWx) an I²C stop condition. |
| i2c.transfer() | Starts a transfer for the specified hardware module. |
| i2c.write() | Write (SW) or queue (HWx) data to the I²C bus. |
| i2c.slave.on() | Registers or unregisters an event callback handler. |
| i2c.slave.setup() | Initialize the I²C interface for slave mode. |
| i2c.slave.send() | Writes send data for the master into the transmit buffer. |
Code of ESP32 I2C Scanner
- In this code used to can the i2c Devices
- Used Software i2c and GPIO-23 as SDA and GPIO-22 as SCL of I2C Device
- Connected DS3231 Device and check i2c address of DS3231
-- setup
id = i2c.SW -- Software
pinSDA = 23 -- 1~12, IO index
pinSCL = 22 -- 1~12, IO index
speed = i2c.SLOW -- only i2c.SLOW supported
--Initialize
i2c.setup(id, pinSDA, pinSCL, speed) -- Initialize the I²C module.
print("Scanning Started....")
for count = 0,127 do
i2c.start(id) -- Send an I²C start condition.
Status = i2c.address(id, count, i2c.TRANSMITTER) -- Setup I²C address and read/write mode for the next transfer.
i2c.stop(id) -- Send an I²C stop condition.
if Status == true then
print("Addrss - "..count.." Detected device address is 0x" .. string.format("%02x", count) .. " (" .. count ..")")
elseif Status == false then
print("Addrss - "..count.." nil")
end
end
print("Scanning End")
Results
Scanning Started.... Addrss - 0 nil Addrss - 1 nil Addrss - 2 nil Addrss - 3 nil Addrss - 4 nil Addrss - 5 nil Addrss - 6 nil Addrss - 7 nil Addrss - 8 nil Addrss - 9 nil Addrss - 10 nil Addrss - 11 nil Addrss - 12 nil Addrss - 13 nil Addrss - 14 nil Addrss - 15 nil Addrss - 16 nil Addrss - 17 nil Addrss - 18 nil Addrss - 19 nil Addrss - 20 nil Addrss - 21 nil Addrss - 22 nil Addrss - 23 nil Addrss - 24 nil Addrss - 25 nil Addrss - 26 nil Addrss - 27 nil Addrss - 28 nil Addrss - 29 nil Addrss - 30 nil Addrss - 31 nil Addrss - 32 nil Addrss - 33 nil Addrss - 34 nil Addrss - 35 nil Addrss - 36 nil Addrss - 37 nil Addrss - 38 nil Addrss - 39 nil Addrss - 40 nil Addrss - 41 nil Addrss - 42 nil Addrss - 43 nil Addrss - 44 nil Addrss - 45 nil Addrss - 46 nil Addrss - 47 nil Addrss - 48 nil Addrss - 49 nil Addrss - 50 nil Addrss - 51 nil Addrss - 52 nil Addrss - 53 nil Addrss - 54 nil Addrss - 55 nil Addrss - 56 nil Addrss - 57 nil Addrss - 58 nil Addrss - 59 nil Addrss - 60 nil Addrss - 61 nil Addrss - 62 nil Addrss - 63 nil Addrss - 64 nil Addrss - 65 nil Addrss - 66 nil Addrss - 67 nil Addrss - 68 nil Addrss - 69 nil Addrss - 70 nil Addrss - 71 nil Addrss - 72 nil Addrss - 73 nil Addrss - 74 nil Addrss - 75 nil Addrss - 76 nil Addrss - 77 nil Addrss - 78 nil Addrss - 79 nil Addrss - 80 nil Addrss - 81 nil Addrss - 82 nil Addrss - 83 nil Addrss - 84 nil Addrss - 85 nil Addrss - 86 nil Addrss - 87 Detected device address is 0x57 (87) Addrss - 88 nil Addrss - 89 nil Addrss - 90 nil Addrss - 91 nil Addrss - 92 nil Addrss - 93 nil Addrss - 94 nil Addrss - 95 nil Addrss - 96 nil Addrss - 97 nil Addrss - 98 nil Addrss - 99 nil Addrss - 100 nil Addrss - 101 nil Addrss - 102 nil Addrss - 103 nil Addrss - 104 Detected device address is 0x68 (104) Addrss - 105 nil Addrss - 106 nil Addrss - 107 nil Addrss - 108 nil Addrss - 109 nil Addrss - 110 nil Addrss - 111 nil Addrss - 112 nil Addrss - 113 nil Addrss - 114 nil Addrss - 115 nil Addrss - 116 nil Addrss - 117 nil Addrss - 118 nil Addrss - 119 nil Addrss - 120 nil Addrss - 121 nil Addrss - 122 nil Addrss - 123 nil Addrss - 124 nil Addrss - 125 nil Addrss - 126 nil Addrss - 127 nil Scanning End >
ESP32 NodeMCU I2C Interface: Code Explanation
This table format provides a structured breakdown of each section of the code along with its explanation.
| Section | Explanation |
|---|---|
| Setup Section | |
| id | Defines the I2C interface as software-based. |
| pinSDA | Specifies the GPIO pin used for the data line (SDA) of the I2C interface. |
| pinSCL | Specifies the GPIO pin used for the clock line (SCL) of the I2C interface. |
| speed | Sets the speed of the I2C communication to slow. Only i2c.SLOW speed is supported. |
| Initialization | |
| i2c.setup() | Initializes the I2C module with the specified parameters: interface ID, SDA pin, SCL pin, and speed. |
| Scanning for Devices | |
| print(“Scanning Started….”) | Prints a message indicating the start of device scanning. |
| Looping through device addresses | Iterates through device addresses from 0 to 127. |
| i2c.start() | Sends an I2C start condition. |
| i2c.address() | Sets up the I2C address and read/write mode for the next transfer. |
| i2c.stop() | Sends an I2C stop condition. |
| Check Status | Checks the status of the address detection: If Status is true, prints the detected device address in hexadecimal and decimal format. If Status is false, prints “nil” for the address. |
| print(“Scanning End”) | Prints a message indicating the end of device scanning. |
Suggest
- ESP8266 NodeMCU Module – I2C : https://aruneworld.com/embedded/esp8266/esp8266-nodemcu/esp8266-nodemcu-module-i2c/
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Embedded Protocol – I2C
I²C (Inter-Integrated Circuit) is a bi-directional two wires and serial data transmission communication protocol developed by Philips (Now NXP Semiconductor) in 1982. I2C is a Half-duplex communication protocol – (I2c can’t send and receive same time in the bus-data line). Multi-master can communicate with multi-salve. (Note: Communication is restricted between two masters; however, a single master can communicate with either a single slave or multiple slaves.) I2C is a Level Triggering. A device that sends data onto the bus is defined as a transmitter, and a device receiving data is defined as a receiver.
The bus must be controlled by a master device, responsible for generating the Start and Stop conditions. In contrast, certain devices such as LCDs, EEPROMs, and RTCs function as slaves. It’s important to note that both master and slave devices can operate as either transmitters or receivers. However, the master device plays a pivotal role in determining which mode is activated.