Example 12: UART Serial Communication

Experiment Overview

Implement serial communication between ESP32 and external devices via UART (Universal Asynchronous Receiver-Transmitter). ESP32 has 3 UART ports, FastBee supports configuring serial ports for debug output, Modbus communication or custom data exchange.

Hardware Wiring

UART Port	TX Pin	RX Pin	Purpose
UART0	GPIO1	GPIO3	USB debug output
UART1	GPIO16	GPIO17	Modbus/External devices
UART2	GPIO18	GPIO19	Extended serial port

UART0 is used for USB debug output by default, UART1/2 can be used to connect external devices.

JSON Configuration Example

{
  "peripherals": [
    {
      "id": "uart0",
      "name": "Serial0-Debug",
      "type": 1,
      "enabled": false,
      "pins": [1, 3],
      "params": {
        "baudRate": 115200,
        "dataBits": 8,
        "stopBits": 1,
        "parity": 0
      }
    },
    {
      "id": "uart1",
      "name": "Serial1-Modbus",
      "type": 1,
      "enabled": false,
      "pins": [16, 17],
      "params": {
        "baudRate": 9600,
        "dataBits": 8,
        "stopBits": 1,
        "parity": 0
      }
    }
  ]
}

Parameter Description

Parameter	Description	Options
baudRate	Baud rate	9600, 19200, 38400, 57600, 115200
dataBits	Data bits	7, 8
stopBits	Stop bits	1, 2
parity	Parity	0=None, 1=Odd, 2=Even

Peripheral Execution Linkage

Scenario: Serial Data Send (Platform Trigger)

Function: Send data to external device via UART1 through cloud platform command

Web Interface Configuration Steps

Step 1: Create Rule

1. Click Peripheral Execution in the left menu
2. Click New Rule button
3. Fill in basic configuration:
   • Rule Name: Serial Send Data
   • Report Data: ✅ Enable
   • Enabled: ✅ Enable

Step 2: Configure Trigger

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Platform Trigger	Receive cloud platform commands
   Operator	Select Set Mode	Received data as action parameters

Step 3: Configure Action

1. Click Add Action button

2. Fill in:

   • Action Type: Select Serial Send
   • Target Peripheral: Select uart1

3. Click Save button

Test Method:

Send any string via cloud platform, e.g.: Hello UART Data will be sent through UART1's TX pin (GPIO16)

UART Parameter Reference

Parameter	Description	Options
Baud Rate	Communication speed	9600, 19200, 38400, 57600, 115200
Data Bits	Number of data bits	7, 8
Stop Bits	Number of stop bits	1, 2
Parity	Parity method	None, Odd, Even

Notes

1. UART0 Occupied: UART0 (GPIO1/3) is used for USB debug, not recommended to reassign
2. Pin Mapping: ESP32 UART TX/RX can be mapped to any GPIO (except GPIO6-11)
3. Voltage Matching: ESP32 is 3.3V level, level shifting needed for 5V devices
4. Modbus Configuration: When used for Modbus, baud rate is typically 9600, must match slave device
5. Buffer: UART receive buffer defaults to 256 bytes, read promptly for large data volumes
6. ESP32-S3: S3's UART0 outputs via USB CDC, physical UART starts from UART1