ESP32-S31 RF Testing and Certification

RF performance and regulatory compliance are required before a wireless product can ship. During development, factory calibration, and certification, you need to measure transmit power, receive sensitivity, frequency offset, and harmonics.

Espressif provides the ESP RF Test Tool for RF tuning and certification workflows.

RF Test Toolkit

Core Tools

  • EspRFTestTool: PC software for RF tuning and sending test commands to the device.
  • Flash Download Tool: Flashes RF test firmware (for example, RF_Test_FW.bin) so the chip runs in RF test mode instead of the application firmware.
  • PowerLimitTool: Configures per-channel transmit power limits for regulatory compliance.

ESP32-S31 RF Calibration

Supports calibration across:

  • Wi-Fi 6 (802.11ax)
  • Bluetooth Classic
  • Bluetooth LE 5.4
  • 802.15.4 (Thread / Zigbee 3.0)

Use a professional RF tester to measure maximum transmit power, receive sensitivity (PER), and center frequency offset.

Certification Testing

For FCC, CE, SRRC, WFA, and Bluetooth SIG tests, use EspRFTestTool to send fixed-frequency commands and put the chip into continuous TX, modulated TX, or continuous RX modes.

After lab tuning, use PowerLimitTool to create an RF power table and program limits into eFuse so production devices stay within regulatory limits.

Documentation

For RF test firmware, fixed-frequency commands, and PowerLimitTool usage, see the Espressif RF Test Guide.

Design and Lab Recommendations

  1. Reserve RF test access on the PCB: Add test pads on the 50-ohm antenna feed line, or solder a 1st- or 3rd-generation IPEX connector so you can route RF signals to a tester with minimal loss.
  2. Use a shield box: Place the device under test in an RF shield box during sensitivity measurements to reduce interference from ambient Wi-Fi, 4G, and 5G signals.
  3. Use professional RF equipment: Certification labs typically use LitePoint IQxel testers or Keysight spectrum analyzers to measure EVM, spectral mask, and frequency offset.