ESP8266 Series Description GP102, GPI00 and MTDO are used to select the boot mode and SDIO mode; for GP100 download mode: pull low externally, run mode: suspend or pull high externally; UOTXD should avoid being pulled low externally during power-up; 3. frequency. If the printing information affects the device function, it is recommended to exchange UOTXD and UORXD with UORTS (MTDO) and UOCTS (MTCK) respectively during power-up to block the printing. ESP32/ESP32-S Series Description Need to use BOOT (GP100) and EN (CHIP PU) pins, the minimum system needs to be reserved where GO is connected to the BOOT pin of the download module. EN pin, high: chip enable; low: chip shutdown; note: do not let E N pin is floating. ESP32-C Series Description 1. ESP32-C3 is released in 2020, with strong performance. ESP32-C3 is a very low power SoC with RISC-V 32-bit single core processor. 2. GP109 is connected to internal weak pull-up by default. If this pin has no external connection or the connected external line is in high impedance state, the latch value is "1". 3. The BOOT pin is I09, so the BOOT pin of the burn-in module needs to be connected to pin 09 of ESP32-C3 (v1.1 motherboard). uarto is used to download firmware and output logs.