Microcontroller Wired Communications

Introduction

Microcontrollers communicate with other devices via wired communication protocols for data exchange. Each protocol serves different purposes, from low-speed, point-to-point communication to high-speed, multi-device networking. This guide covers popular wired protocols, including: UART, RS-232, I²C, SPI, Ethernet, CAN, RS-485, LIN, USB, and I²S.

UART is a simple, asynchronous protocol that uses two lines: TX (Transmit) and RX (Receive). It is commonly used for direct, point-to-point communication between microcontrollers or with peripherals such as GPS modules.

Basic Wiring

Microcontroller A      Microcontroller B
      TX  ---------------->   RX
      RX  <----------------   TX
        

RS-232 is a standardized serial protocol widely used for communication between computers and microcontrollers. It uses a single-ended signal over a three-wire connection: TX, RX, and GND. Unlike UART, RS-232 defines voltage levels and hardware requirements.

Basic Wiring

Microcontroller       PC/Device
    TX  ---------------->  RX
    RX  <----------------  TX
   GND  ---------------->  GND
        

I²C is a two-wire protocol (SDA for Data, SCL for Clock) commonly used to connect sensors, displays, and other peripherals. Multiple devices can share the same bus, identified by unique addresses.

Basic Wiring

Master MCU       Slave Device 1       Slave Device 2
   SDA  ---------------->   SDA  ---------------->  SDA
   SCL  ---------------->   SCL  ---------------->  SCL
        

SPI is a high-speed, full-duplex communication protocol that uses four wires: MOSI, MISO, SCK, and SS. It is widely used in applications requiring fast data transfer, such as SD card modules.

Basic Wiring

Master MCU       Slave Device
   MOSI  ---------------->  MOSI
   MISO  <----------------  MISO
   SCK   ---------------->  SCK
   SS    ---------------->  SS
        

Ethernet allows microcontrollers to connect to local area networks (LAN) for fast communication using the TCP/IP protocol. Modules like the ENC28J60 or W5100 often handle Ethernet communication for microcontrollers.

CAN is a robust protocol designed for real-time communication in automotive and industrial systems. It uses differential signaling over two wires: CANH and CANL, making it highly resistant to noise.

Basic Wiring

Device 1       Device 2       Device 3
  CANH  ---------------->  CANH  ---------------->  CANH
  CANL  ---------------->  CANL  ---------------->  CANL
        

RS-485 is a differential communication protocol suited for long-distance and multi-device communication. It uses two lines, A and B, to transmit data, supporting up to 32 devices on the same bus.

Basic Wiring

Device 1       Device 2       Device 3
   A   ---------------->   A   ---------------->   A
   B   ---------------->   B   ---------------->   B
        

LIN is a single-wire, master-slave protocol primarily used in automotive applications for low-cost and low-speed communication between devices such as car door controllers.

USB is a universal communication protocol for connecting microcontrollers to computers or other USB-capable devices. It supports both data transfer and power delivery. Microcontrollers often use USB to act as virtual COM ports or HID devices.

Basic Wiring

Microcontroller       PC/Host
     D+  ---------------->  D+
     D-  ---------------->  D-
    GND  ---------------->  GND
        

I²S is a protocol used for digital audio communication between microcontrollers and audio devices such as DACs or ADCs. It uses three lines: SD (Serial Data), WS (Word Select), and SCK (Clock).

Basic Wiring

Master MCU      Audio Device
    SD   ---------------->  SD
    WS   ---------------->  WS
   SCK   ---------------->  SCK
        

Conclusion

Microcontroller communication protocols provide flexibility to interface with various peripherals. Whether you're working on low-speed, robust systems with RS-485, real-time systems with CAN, or high-speed networking with Ethernet, selecting the right protocol depends on your application's needs.