Fangrui Product Details 25mhz High Speed Crystal Oscillator 32.768khz 6pf Low Speed Crystal Oscillator V3.0 Version Began To Use Lead-free Process, The Pin Header Is Gold-plated Pin Header, More Environmentally Friendly Flash Pads Have Been Reserved And Usbdisk Fatffs Routines Are Provided Weact Hid Fw Bootloader Has Been Burned Out Of The Factory. It Is A Special Factory Test Version, And Hex Is Not Provided. Support Micropython Programming, Provide Available Micropython Firmware, See The Link For Configuration Files, But Do Not Provide Technical Answers! Boards With Version V1.3 And Above Have 3 Buttons, Reset Button, Boot0 Button, And User Buttons. How To Enter Isp Mode Method 1: Press And Hold The Boot0 Button And The Reset Button Under The Power-on State, Then Release The Reset Button, And Release The Boot0 Button After 0.5 Seconds Method 2: Hold Down The Boot0 Key When Power Is Off, And Release The Boot0 Key 0.5s After Power On Dfu Mode: Just Use The Data Cable To Connect To The Computer, If There Is A Problem Of Unreco