# 6.Troubleshooting

1\. Errors occur when the Keyestudio V4.0 board burns code.

- Please check whether the Arduino Uno board model is correct.
- Please check USB serial number is correct.

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2\. After connecting the Keyestudio V4.0 board to the computer via Micro USB cable, there is no serial port.

Check whether the Keyestudio V4.0 board is properly connected to the computer. Click “Device Manager” to check the serial port. If there is no problem on the port, it means they are connected. If there is no port, the USB chip on the board might be broken.

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3\. After burning code, sensors/modules do not work, or the serial monitor prints wrong messages.

Check whether the connected pins are consistent with pin numbers in codes. If not, please wire up according to codes.

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4\. Servo does not work.

- The voltage may be too low to drive it. An external power supply is required. 
- Or, the servo may be stuck. Before installing the servo, it need a calibration to set its angle to 0 degree. 
- The cover lid may get the wire stuck.

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5\. The fan does not work and the board is very easy to burn out.

When the fan is rotating, it requires a great amount of current, which will cause voltage and current fluctuations in the circuit. Especially when the fan changes its rotation directions, excessive fluctuations can lead to too low voltage and current on the ESP32 board, resulting in a reset. An external power supply is required to power the Keyestudio V4.0 board to ensure that the fan can work normally.

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6\. The LED does not light up after burning the code.

Check whether the connected pins are consistent with pin numbers in codes. If not, please wire up according to codes.

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7\. Sometimes the button can be detected, and sometimes it cannot

Modify the delay for jitter elimination and set it to an appropriate delay.

```c++
 //The software eliminates button jitter
    delay(10);  //delay
```



8\. The ultrasonic detection distance is inaccurate.

It starts measuring from the emitter of the ultrasonic wave. This module is not a high-precision ultrasonic distance detection module so may have errors.

![Img](./media/cou69.png)

9\. The response is very slow when remotely operating other sensors on the web page.

The reasons for slow network transmission in routers:

- When multiple people are connected and the router CPU resources are insufficient, restart the router and reconnect.
- The router system has been in use for too long. Restart the router.
- Do not use it through walls when there is wireless interference or the wireless signal is unstable.

For knowledge related to routers, please **Google** it by yourself.

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