#The7thLiChuangElectricityContest#USB Ammeter (6-24V)

* 1. Project function introduction
USB ammeter, used to check the current and voltage when USB is working. Adopt the official DCDC solution, BL9342 converts to 3.3V, the actual measurement range is 6-24V, and the main control chip cannot work when it is lower than 6V.
The LM2596 voltage stabilization solution is designed, but it is abandoned due to the large volume.
*2. Project attributes
Participate in the Jiali Chuang summer training camp and reproduce the 24V ammeter case.
The official case is as follows:
[Training Camp Official Case] ​​USB Ammeter-Jialichuang EDA Open Source Hardware Platform (oshwhub.com)
*3. Hardware part

1. Buck solution
Adopt the DCDC buck solution to stabilize the voltage at 3.3V to power the MCU.
LM2596-3.3 reference solution (not used)
 
2. The burning program
uses an external method to download the program.
Use the official host computer to download the program through the serial port.
 
Note: When downloading the program through the serial port, you must first pull the BOOT bit high to enter the BOOT mode. The TX of the serial port tool may backflow current to the chip, causing failure to enter the BOOT state. This can be solved by pulling up to enter the BOOT mode and then connecting the serial port.
 
* 3. Some pictures show
that the buck chip cannot work below 6V, and there is no high-voltage working equipment at hand, so the MCU is powered by an external 3.3V to achieve the measurement effect.