set cpu freq in ESP32Board.h

platformio.ini

@@ -31,6 +31,8 @@ extends = arduino_base
 platform = espressif32
 monitor_filters = esp32_exception_decoder
 extra_scripts = merge-bin.py
+build_flags = ${arduino_base.build_flags}
+;  -D ESP32_CPU_FREQ=80          ; change it to your need
 build_src_filter = ${arduino_base.build_src_filter}
 
 ; ================
@@ -126,7 +128,6 @@ build_flags =
   -D SX126X_DIO3_TCXO_VOLTAGE=1.8
   -D SX126X_CURRENT_LIMIT=130.0f  ; for best TX power!
   -D SX126X_RX_BOOSTED_GAIN=true
-  -D ESP32_CPU_FREQ=240
 build_src_filter = ${esp32_base.build_src_filter}
 lib_deps =
   ${esp32_base.lib_deps}