Connect STK500 → Tools → Program AVR → Auto Verify → Flash.
The drivers included with 4.19 (Jungo/WinDriver) often conflict with modern Microchip Studio drivers. If using an AVRISP mkII or Dragon, you may need to use to replace the driver with libusb-win32 or install the Microchip Driver Bundle AVR Freaks 💾 Download Links Full Installer (4.19.730) Microchip Archive AVR Toolchain (GCC) Microchip Toolchain Archive WinAVR (Alternate) SourceForge avr+studio+419+hot
As the final iteration of the series, 4.19 integrated all previous service packs into a single installer and introduced several key features for embedded developers: Native Toolchain Integration : This was the first version to officially support the Atmel AVR Toolchain Connect STK500 → Tools → Program AVR →