ESP32 UART

Introduction to UART

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UART（Universal Asynchronous Receiver/Transmitter）序列埠

BASICS OF UART COMMUNICATION

DB9 Connector

Protocol 通訊協定

• Standard Packet : 8 data bits, even parity, 1 stop bit
  • If the parity bit is a 0 (even parity), the 1 bits in the data frame should total to an even number.
  • If the parity bit is a 1 (odd parity), the 1 bits in the data frame should total to an odd number. RS232 的Vpp電壓較高，有 6V~30V；UART 則是較低的 3.3V 或 5V
    RS232 為負邏輯， UART 為正邏輯，因此兩者波形是反相的
    Baud Rate
    

The main differences between RS-232, RS-422 and RS-485

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NodeMCU-32S pinout

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Arduino Serial

• if(Serial): Indicates if the specified Serial port is ready.
• available(): Get the number of bytes (characters) available for reading from the serial port.
• availableForWrite()
• begin()
• end()
• find()
• findUntil()
• flush():Waits for the transmission of outgoing serial data to complete.
• parseFloat(): Serial.parseFloat() returns the first valid floating point number from the Serial buffer.
• parseInt(): Looks for the next valid integer in the incoming serial.
• peek(): Returns the next byte (character) of incoming serial data without removing it from the internal serial buffer.
• print()
• println()
• read()
• readBytes()
• readBytesUntil()
• readString()
• readStringUntil()
• setTimeout(): Serial.setTimeout() sets the maximum milliseconds to wait for serial data. It defaults to 1000 milliseconds.
• write()
• serialEvent(): Called when data is available. Use Serial.read() to capture this data.

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[Homework]: UART_read.ino

int incomingByte = 0; // for incoming serial data

void setup() {
  Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
  Serial.println("Serial port begin at baud=9600...");
}

void loop() {
  // reply only when you receive data:
  if (Serial.available() > 0) {
    // read the incoming byte:
    incomingByte = Serial.read();

    // show what you got:
    Serial.print("Received: ");
    Serial.println(incomingByte, HEX);
  }
}

• Create code
• run on NodeMCU-32S & enter “Hello” on serail monitor to verify

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[Homework]: Examples>04.Communication>SerialPassThrough

• Verify SerialPassThrough.ino
• Connect TX1 to RX1 * Keyin text on serial-monitor to test it

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Arduino SoftwareSerial

• SoftwareSerial()
• available()
• begin()
• isListening()
• overflow()
• peek()
• read()
• print()
• println()
• listen()
• write()

#include <SoftwareSerial.h>

SoftwareSerial mySerial(2, 3); // RX, TX

void setup()
{
  // Open serial communications and wait for port to open:
  Serial.begin(115200);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Native USB only
  }


  Serial.println("Goodnight moon!");

  // set the data rate for the SoftwareSerial port
  mySerial.begin(38400);
  mySerial.println("Hello, world?");
}

void loop() // run over and over
{
  if (mySerial.available())
    Serial.write(mySerial.read());
  if (Serial.available())
    mySerial.write(Serial.read());
}

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Peripheral/Sensor using UART

This site was last updated June 18, 2023.