power delivery circuit
power coming from terminals or from usb
1- in the terminal we use diode D3 to reverse polarity protection before it going to the voltage regulator
2- at the same time the power coming from USB it connected with SP0503 IC it used for ESD protection (figure 3)
3- 5v from the termianals or USB going to voltage regulator Vin to get 3.3v in Vout.
USB to UART and auto program circuits
1- VBUS connected directly with USB Vcc
2-D+ and D- connected with D+ and D- with USB
3-GND connected with USB GND
in ESP32 once you pull IO0 and EN down you will get this message
rst:0x1 (POWERON_RESET),boot:0x3 (DOWNLOAD_BOOT(UART0/UART1/SDIO_REI_REO_V2))
waiting for download
ets Jun 8 2016 00:22:57cp2102 and ch340g have DTR(Data Terminate Ready) and RTS(Request To Send) it used like handshake between cp2102 and ESP
once RTS become high and DTR low the GPIO0 pull to low and when DTR become high and RTS low EN pull to low
