If you have access to a logic analyzer or an oscilloscope:
FSK stands for , a modulation scheme used to transmit digital data. In the context of this error, your software is looking for an FSK signal from a connected device, but it cannot find one. The solution often involves a specific sequence of connecting a USB cable, pressing a button (like a PTT or Reset), or configuring driver settings. no fsk detected connect usb to download fsk
For STM32 Blue Pill/Black Pill boards:
: If the device is old, a new internal battery may be required before the FSK will stay "saved". Check Hardware Contacts If you have access to a logic analyzer
The software was set to "TH-UV88 (FSK)," but the radio required "TH-UV88 (Serial)." Fix: Changed communication protocol in software settings from "FSK" to "Standard Serial." For STM32 Blue Pill/Black Pill boards: : If