Working with ESP32S3

This chapter contains the following sections. Please read as needed:

Setting Up Development Environment
Example

Setting Up Development Environment

1. Installation and Configuration

For setting up the ESP32S3 environment and basic usage, please refer to the following links:
- ESP-IDF
- Arduino ESP32
Once the environment is set up, you can connect the LoRa module and download the example programs

Hardware Connection

Connect according to the table below.

Core2021-XF	ESP32S3
CLK	40
MISO	46
MOSI	45
CS	42
DIO11	38
RESET	39
BUSY	41

Example

ESP32S3 example programs are located in the core2021-xf\examples\esp32s3 directory of the example package.
Examples 01, 02, and 03 require two Core2021-XF modules: one for transmission and one for reception.

Example	Basic Description	Dependency Library
01_lr2021_tx	LR2021 Transmit	RadioLib
02_lr2021_rx	LR2021 Receive	RadioLib
03_lr2021_pingpong	LR2021 Ping‑Pong	RadioLib
04_lr2021_tx_cw	LR2021 CW Mode Transmit	RadioLib
05_lr2021_LoRaWAN	LoRaWAN	RadioLib

Run Arduino ESP32 Example

Navigate to core2021-xf\examples\esp32s3\arduino and select the example program you wish to test.
Select the development board:
Select the port for the ESP32S3, then compile and upload.
After the upload is completed, open the serial port monitor, and the relevant information will be output.

01_lr2021_tx

Example Description

Based on the ESP32S3 + Core2021-XF module, implements periodic LoRa packet transmission using interrupts.
Custom SPI pins (CLK/MOSI/MISO) to match the ESP32S3 hardware design.
Uses non‑blocking transmission, does not occupy CPU resources in the main loop.
After each packet is sent, automatically delays 1 second before sending the next packet.
Supports string data transmission, with a built‑in packet sequence number for easy debugging.

Code Analysis

SPI.begin(...): Initializes ESP32S3 hardware SPI pins with custom CLK/MOSI/MISO.
radio.irqDioNum = 11: Configures the LR2021 interrupt mapping pin; must be set before initialization.
radio.XTAL = true: Enables the external crystal oscillator to ensure frequency accuracy.
setFlag(void): Interrupt callback function triggered automatically after the module finishes transmission, sets a transmission‑complete flag.
radio.setPacketSentAction(setFlag): Binds the transmission‑complete interrupt function.
radio.startTransmit("content"): Starts asynchronous LoRa transmission (supports string / byte array).
radio.finishTransmit(): Cleanup after transmission, turns off the transmit circuit and resets the module state.
loop() main logic: Check transmission‑complete flag → print status → delay → send next packet with sequence number.

Operation Result

After compiling and uploading, open the serial monitor to see logs indicating transmission completion, as shown below (in combination with 02_lr2021_rx):

02_lr2021_rx

Example Description

Based on the ESP32S3 + Core2021-XF module, implements wireless LoRa packet reception using interrupts.
Custom hardware SPI pins to match the ESP32S3 hardware design.
Uses non‑blocking listening mode; the module automatically waits for data without consuming CPU resources.
After successful reception, automatically parses the data and prints the packet content, RSSI, and SNR.
The same frequency, spreading factor, bandwidth, and coding rate must be configured on both the transmitter and receiver for successful communication.

Code Analysis

SPI.begin(...): Initializes ESP32S3 hardware SPI with custom CLK/MOSI/MISO pins.
radio.irqDioNum = 11: Configures the LR2021 interrupt mapping pin; must be set before initialization.
radio.XTAL = true: Enables the external crystal oscillator to ensure frequency accuracy and improve reception stability.
setFlag(void): Interrupt callback function triggered automatically after a complete packet is received.
radio.setPacketReceivedAction(setFlag): Binds the reception‑complete interrupt service function.
radio.startReceive(): Starts continuous LoRa reception mode, enters a data‑waiting state.
radio.readData(str): Reads the received wireless data (supports string parsing).
radio.getRSSI() / radio.getSNR(): Retrieves signal quality parameters for debugging and link evaluation.
loop() main logic: Check reception‑complete flag → read data → parse and print → continue listening.

Operation Result

After compiling and uploading, open the serial monitor to see real‑time reception logs including data content, RSSI, and SNR, as shown below (in combination with 01_lr2021_tx):

03_lr2021_pingpong

Example Description

Based on the ESP32S3 + Core2021-XF module, implements LoRa automatic ping‑pong (question‑answer) two‑way communication.
Custom hardware SPI pins to match the ESP32S3 hardware design.
Two modules can send and receive to each other without manual control.
Enabling INITIATING_NODE sets the module as the initiator; the other module acts as the responder.
Automatically switches between transmit and receive states, driven by non‑blocking interrupts.

Code Analysis

SPI.begin(...): Initializes ESP32S3 hardware SPI with custom CLK/MOSI/MISO pins.
radio.irqDioNum = 11: Configures the LR2021 interrupt mapping pin; must be set before initialization.
radio.XTAL = true: Enables the external crystal oscillator to ensure communication frequency accuracy.
setFlag(void): General interrupt callback, triggered on either transmit or receive completion.
radio.setIrqAction(setFlag): Binds the shared transmit/receive interrupt function.
INITIATING_NODE macro: Used to distinguish the initiating node.
radio.startTransmit(): Starts packet transmission.
radio.startReceive(): Switches the module to listening (receive) mode.
radio.readData(str): Reads the received LoRa packet.
loop() main logic: Transmit complete → enter receive; receive complete → delay reply → transmit again.

Operation Result

Flash the program onto two modules, enabling the INITIATING_NODE macro on one of them.
After power‑on, they automatically send and receive to each other; the serial monitor prints the transmit/receive status, data, RSSI, and SNR, as shown below:

04_lr2021_tx_cw

Example Description

Based on the ESP32S3 + Core2021-XF module, implements LoRa continuous wave (CW) / direct transmit.
Custom SPI pins to match the ESP32S3 hardware design.
Outputs a fixed‑frequency carrier signal without packet formatting, used for band testing, signal detection, and instrument calibration.
Fixed frequency 868 MHz, transmit power 22 dBm.
Upon power‑up, transmits continuously with no additional logic.

Code Analysis

SPI.begin(...): Initializes ESP32S3 hardware SPI with custom CLK/MOSI/MISO pins.
radio.XTAL = true: Enables the external crystal oscillator to ensure carrier frequency accuracy.
OUT_HZ 868000000UL: Defines the direct transmit frequency (868 MHz); can be modified.
radio.setOutputPower(22): Sets the transmit power to 22 dBm.
radio.transmitDirect(OUT_HZ): Enters continuous direct transmission mode, outputting a fixed‑frequency carrier.
loop(): No business logic; the carrier continues to transmit without program intervention.

Operation Result

After flashing, the module immediately outputs a fixed‑frequency carrier signal.
The serial port prints initialization and transmission start status; a spectrum analyzer or receiving module can detect the continuous RF signal, as shown below:

05_lr2021_LoRaWAN

Example Description

Based on the ESP32S3 + Core2021-XF module, implements LoRaWAN OTAA join + uplink/downlink communication.
Custom SPI pins to match the ESP32S3 hardware design.
Uses NVS flash to store session information, allowing fast reconnection after power‑off reboot without re‑joining.
Periodically uploads random data (default every 5 minutes) and automatically listens for server downlink messages.
Supports printing downlink data in HEX/ASCII formats for easy debugging and link verification.

Code Analysis

SPI.begin(...): Initializes ESP32S3 hardware SPI with custom CLK/MOSI/MISO pins.
radio.irqDioNum = 11: Configures the LR2021 interrupt mapping; must be set before initialization.
radio.XTAL = true: Enables the external crystal oscillator to ensure LoRaWAN frequency accuracy.
prefs.begin(...): Initializes the ESP32 NVS partition for storing LoRaWAN session information.
restoreLoRaWANState(): Restores session information from NVS for fast reconnection.
node.beginOTAA() / node.activateOTAA(): OTAA join functions.
saveLoRaWANState(): Saves session information to NVS after successful join.
node.sendReceive(): Sends uplink data and automatically listens for server downlink messages.
printHex / printAscii: Formats and prints received data.

Operation Result

After flashing, the module automatically completes OTAA join, periodically reports data, and listens for downlink messages.
The serial port prints join status, uplink/downlink messages, signal quality, etc., as shown below: