T-TWR Quick Start

Required Libraries

Library	Version	Source
RadioLib	Latest	GitHub
TinyGPSPlus	Latest	GitHub
U8g2	Latest	GitHub
XPowersLib	Latest	GitHub

Important: T-TWR requires a battery for radio operation. USB alone cannot supply sufficient current for the SA868 RF unit. Always connect a 21700 or 18650 battery before using the radio.

Important: Always connect the RF antenna before powering on. Operating without an antenna may damage the SA868 module.

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Arduino

PlatformIO (Recommended)

1. Install VS Code and the PlatformIO IDE extension
2. Clone the repository:

   git clone https://github.com/Xinyuan-LilyGO/T-TWR.git

3. Open platformio.ini and uncomment the target example under [platformio]
4. Click ✓ to build, connect via USB-C, click → to upload

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Arduino IDE

1. Install ESP32 Board Support

1. Open Arduino IDE → File → Preferences
2. Add to "Additional Board Manager URLs":

   https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

3. Go to Tools → Board → Boards Manager, search esp32, install esp32 by Espressif Systems

2. Install Libraries

Copy all folders from T-TWR/lib to your Arduino libraries directory.

3. Board Settings

Setting	Value
Board	ESP32S3 Dev Module
Upload Speed	921600
USB Mode	Hardware CDC and JTAG
USB CDC On Boot	Enabled
CPU Frequency	240 MHz (WiFi)
Flash Mode	QIO 80 MHz
Flash Size	16 MB (128Mb)
Partition Scheme	16M Flash (3MB APP/9.9MB FATFS)
PSRAM	OPI PSRAM

4. Upload

Click Upload.

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Examples

Example	Description
Factory	Full factory application
GPS_Basic_Example	Basic GPS data display
SA868_ATDebug_Example	SA868 AT command debug
SA868_ESPSendAudio_Example	Radio audio transmission
U8g2_GraphicsTest_Example	OLED graphics test

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Peripheral Examples

SA868 VHF/UHF Radio (AT commands)

// SA868 connected via UART — check T-TWR schematic for pins
HardwareSerial sa868(1);

void setup() {
  Serial.begin(115200);
  sa868.begin(9600, SERIAL_8N1, /*RX=*/16, /*TX=*/15);
  delay(500);
  // Set frequency (UHF example: 433.000 MHz TX/RX)
  sa868.println("AT+DMOSETGROUP=0,433.0000,433.0000,0000,1,0000");
  delay(200);
  while (sa868.available()) Serial.write(sa868.read());
}

void loop() {
  // PTT: drive PTT pin LOW to transmit, HIGH to receive
}

GPS (via TinyGPSPlus)

#include <TinyGPSPlus.h>

TinyGPSPlus gps;
HardwareSerial gpsSerial(2);

void setup() {
  Serial.begin(115200);
  gpsSerial.begin(9600, SERIAL_8N1, /*RX=*/3, /*TX=*/1);
}

void loop() {
  while (gpsSerial.available()) gps.encode(gpsSerial.read());
  if (gps.location.isUpdated()) {
    Serial.printf("Lat: %.6f Lng: %.6f Sats: %d\n",
      gps.location.lat(), gps.location.lng(), gps.satellites.value());
  }
}

OLED Display (U8g2)

#include <U8g2lib.h>
#include <Wire.h>

U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, U8X8_PIN_NONE);

void setup() {
  u8g2.begin();
}

void loop() {
  u8g2.clearBuffer();
  u8g2.setFont(u8g2_font_ncenB08_tr);
  u8g2.drawStr(0, 20, "T-TWR Ready");
  u8g2.sendBuffer();
  delay(1000);
}

PMU (AXP2101 via XPowersLib)

#include <XPowersLib.h>

XPowersPMU pmu;

void setup() {
  Serial.begin(115200);
  Wire.begin();
  if (!pmu.begin(Wire, AXP2101_SLAVE_ADDRESS)) {
    Serial.println("PMU init failed");
    return;
  }
  Serial.printf("Battery: %d mV\n", pmu.getBattVoltage());
}

void loop() { delay(1000); }

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FAQ

Q: Upload keeps failing?
A: Hold BOOT, press and release RST, then release BOOT to enter download mode.

Q: Radio not transmitting?
A: Ensure a battery is connected (USB power alone is insufficient for RF). Confirm the antenna is attached. Check the SA868 power state via AXP2102 PMU.

Q: UHF or VHF version?
A: T-TWR is available in UHF (400–480 MHz) and VHF (134–174 MHz) variants. Ensure the correct frequency is programmed for your version.