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 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 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 unrecognized, you can properly heat the chip (25 Celsius), and then re-enter the ISP mode Serial port mode:use USB to serial port to connect PA9 and PA10 of the core board WeAct HID FW Bootloader No need for USB to serial port, no debugger, no computer driver, just a TYPE-C data cable to complete the firmware download Press and hold theKEY button, click thereset button, LED C13flashes, release theKEY buttonto enter Model:STM32F411CEU6 Colour:Black Material:PCB Package Contents: 4 x Development Board with pin Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.