AT6668-Based GNSS Device Firmware Upgrade Guide

This guide applies to AT6668-based devices such as Unit GPS v1.1, Unit GPS SMA, and Module GPS v2.0 / v2.1. The upgrade procedure, firmware, and tools are the same across models; only the connector type differs. This guide uses Unit GPS v1.1 as an example to explain the specific upgrade steps and troubleshooting methods.

1. Precautions

To ensure a successful upgrade, do not perform any of the following during the upgrade:

• Power off or reset the device
• Disconnect or reconnect cables or the adapter board
• Close GnssToolKit3

2. Preparation

2.1 Bill of Materials

2.2 Software Preparation

2.3 Firmware File

3. Hardware Connection

3.1 Pin Mapping Table

Using Unit GPS v1.1 as an example, the device provides a HY2.0-4P Grove connector that exposes GND, 5V, and UART signals. For the upgrade, use a Grove to Dupont cable to connect the device to the USB-TTL module. Unit GPS SMA uses exactly the same wiring order.

Module GPS v2.0 / v2.1 uses a 2.54mm pin header. Connect GND, 5V, TX, and RX according to the silkscreen labels on the board.

Wiring Diagram (TX/RX cross-connected, common ground):

   USB-TTL                        Unit GPS v1.1
  ┌──────────┐                   ┌──────────────┐
  │  5V   ●──┼───────────────────┼──● Red 5V    │
  │  GND  ●──┼───────────────────┼──● Black GND │
  │  RXD  ●──┼───────────────────┼──● White TX  │
  │  TXD  ●──┼───────────────────┼──● Yellow RX │
  └──────────┘                   └──────────────┘

3.2 Wiring Precautions

• TX and RX must be crossed: connect the module TX to the adapter RX, and the module RX to the adapter TX.
• The device and USB-TTL module must share a common ground; connecting only TX/RX may cause communication errors or no data output.
• The signal level is 3.3V; set the USB-TTL module to 3.3V, and never connect RS-232 levels (±12V).
• No antenna or satellite positioning is required during the upgrade; it can be completed indoors.
• For pin-header devices, distinguish the power and signal pins to avoid connecting 5V to TX/RX.

4. Driver Installation and Serial Port Detection

1. After installing the USB-TTL driver, connect the USB-TTL module to the computer and open Device Manager.
2. Under Ports (COM & LPT), confirm the newly added serial device, such as USB-SERIAL CH340 (COMx), and note its port number.
3. Close any program that is using the port, such as a serial terminal or an IDE serial monitor.

Serial Port Settings:

5. Firmware Upgrade

1. Complete the wiring described in Chapter 3 and power on the module.

2. Open the GnssToolKit3 directory and double-click GnssToolKit3.exe to run it.

3. Select the corresponding COM port from the port list, set the baud rate to 115200, and click 连接 (Connect).

4. Click 升级导航代码 (Upgrade Navigation Code) to open the firmware upgrade page.

5. Select the firmware file AT6668-ATGM336H_6N74_V6380_20260525-2800.ubf, and confirm that the module model and firmware version are V6.3.8.0.

6. Wait for the upgrade to complete.

7. After a successful upgrade, power off the module and power it on again to complete the restart.

6. FAQ

COM Port Not Displayed in Device Manager

• Reinstall the USB-TTL driver.
• Try another USB cable and USB port.

The Tool Reports That the Serial Port Cannot Be Opened

• Close serial terminals, IDE serial monitors, and other programs that are using the port.
• If the log shows Serial port resource error., the port is in use.

No Output After Opening the Serial Port

• Check whether TX/RX are crossed.
• Confirm that the module and adapter board share a common ground.
• Confirm that the baud rate is 115200.

Garbled Serial Output

• Set the serial port parameters to 115200 8N1.

Upgrade Fails Midway

• Check for loose wiring and unstable power.
• Power cycle the module and perform the upgrade again.

No Data Output from Module GPS

• Check the DIP switch TX/RX setting against the board silkscreen, and connect to the corresponding pins.

7. Related Resources

• Unit GPS v1.1 Product Documentation
• Unit GPS SMA Product Documentation
• Module GPS v2.1 Product Documentation
• Module GPS v2.0 Product Documentation
• ATGM336H-6N Datasheet