Chapter 1: Unboxing and Hardware Overview

1.1 Package Contents

• ESP32JTAG host unit × 1
• USB-C cable × 1
• Port cable assemblies × 4 (each with a dedicated connector on one end and 4 color-coded flying leads on the other)

Note: No printed manual is included. This document is the primary reference.

Fig 1.1 - Unboxing

1.2 Device Overview

Fig 1.2a - Device Front Side Views

Fig 1.2b - Device Back Side Views

• Front: 1.83-inch LCD screen
• One side: USB-C port
• Other side: Port area
• Back: Product label
• BOOT0 / Download Mode Button: A button labeled BOOT0 is located on the top of the device. It is used to enter ROM download mode for USB wired flashing. For factory reset options, see Chapter 4.

1.3 Port Naming and Orientation

The 4 ports are located on the same side of the device, named PA, PB, PC, and PD in sequence. The housing at both ends of the port array is marked with "A" and "D" for orientation reference: the port closest to "A" is PA, the port closest to "D" is PD, and the two ports in between are PB (adjacent to PA) and PC (adjacent to PD).

Fig 1.3 - Ports Close-up

1.4 Port Cable Assembly Description

Each Cable Assembly Consists of Two Parts

Fig 1.4a - Fly-wire Overview

• Device end (dedicated connector): An 8-pin, 2-row dedicated connector with a keying tab on the side that mates with the PCB slot on the device (ports A/B/C/D), providing a hardware-level foolproof design that enforces a single, correct insertion orientation.
• Target board end (flying leads): Each main wire splits into two at the tip (4 pairs, 8 individual wires total):
  • 4 black wires: internally connected together; carry GND to the target board in all operating modes.
  • 4 color-coded wires: red, brown, green, and blue; connect to the corresponding signal pins on the target board.

Pin-to-Color Mapping for Port Connections (Quick Reference)

Fig 1.4b - Pin-to-Color Mapping

To simplify wiring, the device’s pin layout, connector key position, and flying lead colors follow a strict, absolute one-to-one correspondence. Refer to the table below when making connections:

1.5 Port Modes and Pin Functions

Fig 1.5 - Pinout - Mode Mapping

Port Mode Quick Reference

Note: Operating modes are configured and switched through the web interface. Select the required mode before wiring or using a port.

Fig 1.5a - Port Configuration On Website</p>

Mode 1: Logic Analyzer (supported by Port A / B / C / D)

Note: X represents the port letter A/B/C/D.

Mode 2: UART with Target Sensing & Reset Control (Port B only)

Fig 1.5b - SReset Function On Website

Mode 3: Target MCU JTAG/SWD Debugger (Port C only)

The Port C supports both JTAG and SWD interfaces for ARM Cortex MCU debugging with automatic detection (JTAG connection is attempted first, reverting to SWD if unsuccessful).

For using as JTAG port:

For using as SWD port:

Mode 4: FPGA XVC (Port D only)

The Port D supports AMD (Xilinx) FPGA XVC protocol for programming and debugging via Vivado.

Mode 5: Signal Generator (Port D only)

When Port D is configured as a signal generator, it functions as a signal output source for clock injection or circuit excitation. Depending on your target requirements, you can select one of the three sub-modes below.

• Sub-Mode 1: Counter Lo (High-Speed Clock Generation): Drives internal 132 MHz free-counter bits [3:0] onto Port D pins.

• Sub-Mode 2: Counter Hi (Low-Speed Clock Generation): Drives internal 132 MHz free-counter bits [7:4] onto Port D pins.

• Sub-Mode 3: GPIO Direct (Fixed Square Wave Generation): Generates synchronized, low-frequency square waves driven by the internal periodic timer. All 4 pins output the exact same synchronous signal. Wires can be mixed or connected interchangeably.

1.6 Safety Notes

Please read the following safety requirements before using this device.

Voltage limits: The recommended operating voltage range is 1.2 V–3.3 V. Each port is equipped with ESD protection to withstand transient overvoltage, but continuous input exceeding 3.3 V is not recommended.

Adjustable voltage: The target board reference voltage (VTref / VIO_VAR) is controlled by the device’s PWM output and can be configured through the web interface without requiring an external power supply.

Common ground requirement: Regardless of the operating mode, the target board GND must be connected to the ESP32JTAG via the black wire in the cable assembly.

No hot-plugging: Do not insert or remove the cable assemblies while the device or target board is powered; doing so may cause ESD damage.

Power off before wiring: It is recommended to complete all wiring with power removed, then verify all connections before applying power.

Chapter 2: Powering On and Initial Connection

The ESP32JTAG is ready to use immediately after power-on — no driver installation is required. The device automatically broadcasts a Wi-Fi hotspot, and all configuration can be completed through the built-in web interface accessed via a browser. This chapter covers how to power on the device, connect to the hotspot, and access the web interface.

2.1 Power-On and LCD Display Overview

• Connect the device to a power source using the included USB-C cable (a computer USB port, USB charger, or power bank all work).
• The device powers on, the LCD screen lights up, and initial information is displayed:

Fig 2.1 - LCD Startup

Field Descriptions

Note: The characters after the underscore in the SSID (XXYY) are the "device suffix", the last 2 bytes of the device’s MAC address. The suffix is unique to each unit and is also shown on the LCD.

2.2 Connecting to the Device Hotspot (AP Mode)

1. Open the Wi-Fi settings on your computer or smartphone.
2. Search for the hotspot named esp32jtag-XXYY. The device shown in the figure has the suffix 999D.

Fig 2.2 - Wi-Fi List

3. Enter the password esp32jtag to complete the connection.

Note: After connecting to the device hotspot, your computer will temporarily lose access to its previous network. This is expected behavior.

2.3 Accessing the Web Interface

1. Open a browser (Chrome, Edge, or Firefox recommended).
2. Type https://192.168.4.1 in the address bar and press Enter.
3. The browser will display a security warning — this is because the device uses a self-signed TLS certificate and is completely normal.
   Click "Advanced" → "Proceed to 192.168.4.1" (exact wording varies by browser, but the steps are the same).

Fig 2.3a - Browser Warning

4. When the login prompt appears, enter the default credentials:
   • Username: admin
   • Password: admin

Fig 2.3b - Login Page

5. Click Login to enter the main web interface.

2.4 Web Interface Overview

After logging in, five functional tabs are displayed at the top of the interface, providing access to all device operations.

Fig 2.4 - Web Interface

Tab Descriptions

Note: At this point, the device has completed its initial setup and is ready for use.

Chapter 3: Joining a Local Network (Switching to Station Mode)

By default, the ESP32JTAG operates in AP mode, which requires your computer to switch to the device’s hotspot in order to access the web interface. After switching to Station mode, the device joins your existing Wi-Fi network, allowing your computer to access it directly without changing networks — this is the recommended way to use the device on a day-to-day basis. This chapter starts from the AP mode state at the end of the previous chapter and walks through switching to and configuring Station mode.

1. In the web interface, go to System Configurations → Wi-Fi Configuration.
2. Select ST mode and enter the SSID and password of your local Wi-Fi network.
3. Click Save settings & Restart and wait for the device to apply the configuration.

Fig 3.1 - Wi-Fi Configuration

4. After the device reboots, the LCD switches to show ST mode and the newly assigned IP address.

Fig 3.2 - LCD Display Under Station Mode

5. Switch your computer back to your original Wi-Fi network, then access the web interface using the new IP address.

Fig 3.3 - Access Web Interface With New IP

Note: ESP32JTAG currently supports 2.4 GHz Wi-Fi only.

If the device does not appear on your network after switching to Station mode, check the SSID and password first. If you cannot access the web interface, restore factory settings using the procedure in Chapter 4 to return the device to AP mode.

Chapter 4: Wireless Firmware Upgrade (OTA)

The ESP32JTAG supports fully wireless firmware upgrades. The entire process requires no USB cable and can be completed entirely through a browser. This chapter covers how to check the current firmware version, obtain new firmware, perform the upgrade, and recover from unexpected situations.

4.1 Checking the Current Firmware Version

Open the web interface, navigate to the System Configurations tab, and scroll to the Version Information section at the bottom of the page.

Fig 4.1a - Version Information

Alternatively, the top of the Firmware Update tab displays a concise summary of the current firmware (e.g., Current firmware: 0.2.0 (build Apr 3 2026 16:54:59 commit 41f3034)), making it a convenient way to confirm the version before upgrading.

Fig 4.1b - Current firmware

4.2 Obtaining the Latest Firmware

Firmware releases are available at https://github.com/EZ32Inc/esp32jtag_firmware/releases

Each release contains two files, distinguished by their filename suffix:

Example filename format: esp32jtag_v0.2.0_20260403_165459_41f3034_ota.bin, which encodes the version number, build timestamp, and Git commit in sequence for easy version comparison.

Caution: Do not use _full.bin for OTA upgrades. The OTA process only accepts _ota.bin; uploading the wrong file will cause the upgrade to fail.

Note: The device does not check for updates automatically. Users must download the firmware manually and upload it themselves.

4.3 Uploading and Performing the Upgrade

1. Click the Firmware Update tab in the top navigation bar of the web interface.
2. Confirm the current firmware version information shown at the top of the page.
3. Drag and drop the downloaded _ota.bin file into the dashed box in the center of the page, or click the box to manually select the file.
4. Click the Upload & Update button. A progress bar will appear and display the upload status in real time.

Fig 4.3 - Firmware Upload

5. Once the upload is complete, the device automatically finishes the upgrade and reboots.
6. Reconnect to the web interface and verify that the version number has been updated in the Version Information section.

Caution: Do not cut power during the upgrade process. If the upload is interrupted mid-way, the device retains the original firmware and can be safely retried.

4.4 Restoring Factory Settings

If you need to clear all configuration and restore the device to its factory state (Wi-Fi returns to AP mode, all port configurations are reset), there are two methods:

Method 1 (Recommended): Via the Web Interface

On the System Configurations page, click the Set to default button. After confirmation, the device automatically clears all configuration stored in Flash and reboots.

Fig 4.4a - Set to default

Method 2: USB Wired Flashing

If an OTA failure causes firmware corruption or the device enters a boot loop, the web interface will be inaccessible. In this case, recovery must be performed using the browser-based one-click flashing tool.

Use Chrome or Edge for this procedure. The WebSerial flashing tool requires Web Serial support, which is not available in Firefox or Safari. Also make sure the USB-C cable supports data, not only charging.

First, enter Download Mode by following these steps:

1. Power off the device.
2. Press and hold the BOOT0 button without releasing it.
3. Plug in the USB cable to apply power.
4. Hold for approximately 1 second, then release BOOT0.
5. The LCD shows no display (black screen) → the device has entered ROM download mode. This is expected behavior.

Then, complete the browser-based one-click flashing:

1. Open the following page: https://adafruit.github.io/Adafruit_WebSerial_ESPTool/. Click the Connect button on the page.

Fig 4.4b - Adafruit WebSerial ESPTool

2. A small browser dialog will appear (as shown below). Select your device from the list (Windows shows COM3 etc.; Mac shows cu.usbserial), then click Connect. The page will automatically detect the chip.

Fig 4.4c - Chips Detected View

3. Load the firmware and configure the settings:
   • In the Offset field, enter: 0x0.
   • Click Choose a file and select your esp32jtag_vXXX_full.bin file from the dialog.

Fig 4.4d - Firmware Settings

Caution: You must use the _full.bin file here. It is a complete Flash image including the bootloader and partition table. The _ota.bin file is not valid in this mode.

4. Click the Program button and wait for the process to complete.
5. When programming finishes, unplug and reconnect the USB-C cable to reboot the device.
6. Confirm that the LCD turns on and shows AP mode again.
7. Reconnect to the esp32jtag-XXYY hotspot, open https://192.168.4.1, and verify the firmware version in the web interface.