
III. Functional Modules
USB interface is the more common Type-C interface, which can be plugged in either way.
The flashing chip is the common and low-cost CH340C. RX and TX are each connected to an indicator light to indicate the flashing status. A 0 resistor is added to the power supply for easy debugging and maintenance.
The timing of automatic flashing is shown in the figure, which can be referred to the Espressif manual for details. Two buttons are reserved for manual flashing compatibility.
The step-down module is the common and low-cost AMS1117, which can output a current of up to 1A. The rest are standard designs and require no further explanation.
step-down module uses the ETA3409S2F, which can output up to 3A. The choice of resistors R6 and R7 can be based on your needs; here, 100kΩ and 22kΩ are chosen. The calculation formula can be found in the chip's datasheet. Other resistors and capacitors are standard.
This is a 7-pin connector. Pay special attention to the pinout; carefully check this pinout on your custom-designed board!
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