FAQ & Troubleshooting

A: This usually means another program is using the COM port.

• Close any serial terminal program using the port
• Close any other programs using the port (PuTTY, Tera Term, etc.)
• Unplug and replug the USB cable
• Try a different USB port
• Restart the ESP32

A: Check these settings:

• Verify the baudrate matches your ESP32 firmware (common: 115200, 250000)
• Check USB cable is properly connected
• Ensure ESP32 is powered (LED should be on)
• Try different baudrates: 115200, 250000, 9600
• Check Device Manager (Windows) to confirm port is recognized

A: For WiFi connections:

• Ensure you're connected to the ESP32 WiFi network first
• Check IP address (default: 192.168.4.1)
• Check port (default: 82)
• Verify ESP32 is in Access Point (AP) mode
• Check firewall settings on your computer
• Try pinging the ESP32 IP address

A: Possible causes:

• ESP32 may not have the correct firmware — re-flash using the pre-compiled zip from your PRO email
• No CAN traffic on the bus - check if CAN bus is active
• MCP2518FD not initialized — check wiring and try the 40 MHz build if your module uses a 40 MHz crystal
• Wrong CAN bus connection - verify CANH/CANL connections
• For testing without a car: connect 120Ω resistor between CANH and CANL

A: Check hardware connections:

• Verify all SPI pins are connected correctly (GPIO18→SCK, GPIO19→SO, GPIO23→SI, GPIO5→CS)
• Verify power: 3V3 → 3V3 (logic) and VIN → 5V (transceiver rail on typical modules)
• Never connect 5V to the module 3V3 pin
• Verify ground connection (GND to GND)
• Check for loose connections or bad jumper wires
• Try a different MCP2518FD module if available
• Re-flash firmware if the module never responds after wiring checks

• 3V3 → 3V3 for controller logic only
• VIN → 5V for the transceiver rail (required on many AliExpress MCP2518FD breakouts)
• Do not swap these — 5V on the 3V3 pin can damage the module
• Check power connection before testing

A: Use loopback mode:

• Connect a 120Ω resistor between CANH and CANL on the MCP2518FD module
• This simulates a terminated CAN bus for basic bench checks
• For live traffic you need an active vehicle CAN network or approved test equipment

A: Try these solutions:

• Check the log file at %LOCALAPPDATA%\ESP32_CAN_Sniffer\logs\can_sniffer.log for error messages
• Reduce buffer size in Performance Tuning settings
• Close other resource-intensive applications
• Use the crash report feature (About → Report Bug) to send details

A: Optimize performance:

• Increase serial baudrate (up to 1,000,000 bps)
• Reduce GUI update rate in Performance Tuning
• Increase buffer size for longer captures
• Use Serial connection instead of WiFi for better performance
• Close unnecessary applications

A: Check decoding settings:

• Verify correct vehicle database is loaded (Fiat CANB/CANC)
• Check if CAN ID exists in the database
• Enable Highlighting → Debug Output (Performance) to write decoding details to the log file
• Verify database format is correct (byte addressing format)
• Some messages may not have decoders - this is normal

A: For license issues:

• Check internet connection (required for activation)
• Verify license key is correct (copy-paste to avoid typos)
• Check email for activation confirmation
• Ensure hardware hasn't changed significantly
• Contact support: esp32contact@gmail.com

A: The installer from our official site or GitHub releases is the genuine ESP32 CAN Sniffer build from IFIX ELEKTRONIKA. New and independent software often triggers warnings until Windows builds reputation.

• Browser download prompt (Keep / Discard): In Edge, Chrome, Firefox, and others, Windows may ask whether to keep or discard the file. Choose Keep if you started from esp32canbus.pages.dev or the GitHub link above.
• Windows SmartScreen: When you run the installer, SmartScreen may flag it and ask whether you want to run it. Click More info, then Run anyway (or continue setup). The installer is not signed with a commercial certificate yet; that is why SmartScreen appears.
• Microsoft Defender after install: On some systems or fresh VMs, Defender may allow the installer but still block ESP32_CAN_Sniffer.exe on first launch. If that happens, restore/allow the app in Protection history or add the installed app folder as a Defender exclusion.
• Only download from our website or github.com/esp32support/esp32-can-sniffer — not third-party mirrors.
• The installer includes IF_WINDOWS_BLOCKS_THE_APP.txt with the unblock steps if Defender blocks the app after installation.
• If the app shows a Python error on first run, download again — we may have published a fixed build; contact support with a screenshot.

We plan to add standard Windows code signing in a future release to reduce these prompts.

A: The customer release is built for Windows desktop usage.

• Recommended: Windows 10 or Windows 11 (64-bit)
• Likely to work but not officially targeted: older Windows versions (for example Windows 7/8.1)
• If you are on an older OS, use at your own risk and contact support if you hit startup issues

A: No, not for normal customers using the packaged EXE/installer.

• The desktop app (EXE/installer) does not require Python
• Python is only needed once to run pip install esptool when flashing the ESP32 firmware zip
• Install CP210x or CH340 USB drivers if Windows does not show a COM port

A: Install USB drivers:

• CP210x drivers: Download from Silicon Labs
• CH340 drivers: Download CH340 drivers
• Check Device Manager (Windows) to see if device appears as "Unknown Device"
• Try different USB cable (some cables are power-only)
• Try different USB port

A: Use the pre-compiled firmware zip from your PRO follow-up email (not Arduino IDE):

• Install Python 3, then pip install esptool in the unzipped firmware folder
• Run flash.bat COM4 (20 MHz) or flash_40mhz.bat COM4 (40 MHz modules)
• Replace COM4 with your ESP32 port from Device Manager
• Close other programs using that COM port before flashing
• Install CP210x/CH340 drivers if the port is missing
• Hold the ESP32 BOOT button during flash if the board requires download mode