Features
1. 25MHZ high speed crystal oscillator & 32.768Khz 6PF low speed crystal oscillator
2. Flash pads are reserved, providing USBDisk&&FATFFS routines
3. Jumper cap can be used directly without installation. BOOT0 internal 10K resistance pull-down
4. Factory has burned breathing lamp &&USBCDC test procedures.
5. Provide available MicroPython firmware, configuration files
6. Adjust the direction of the jumping cap if it cannot be installed.Because the jump cap is wide on one side and narrow on the other.
7. V1.3 board with 3 buttons: reset key, BOOT0 key and user button.
V1.3 serial download and DFU download: connect to PA9 and PA10 (connect to usb in DFU mode) by pressing BOOT0 key and reset key, and then release the reset key. After 0.5 seconds, release the BOOT0 key to enter serial download or DFU download. The corresponding software is flymcu or CubeProg.

Specifications
STM32F401CEU6/CCU6/CDU6 in UFQFPN48 package
ARM® 32-bit Cortex® -M4 CPU with FPU
100 MHz max CPU frequency
VDD from 1.7 V to 3.6 V
512 KB Flash
128 KB SRAM
GPIO with external interrupt capability
1x12-bit, 2.4 MSPS ADC with 16 channels
DMA Controller
Up to 11 Timers (six 16-bit, two 32-bit, two watchdog timers and a SysTick timer)
USART/UART (3)
I2C (3)
SPI/I2S (5)
SDIO
USB 2.0 full-speed device/host/OTG controller with on-chip PHY
CRC calculation unit
96-bit unique ID
RTC