It has been verified that there are no problems and you can print the board directly.

1. Why make

There are various versions of Arduino nano on the market, and there is no one version that I like.

2. Features

处理器ATmega328p AU (AU指的是封装wire bonding的时候用的是金丝)
工作电压 5V
输入电压（推荐） 7-12V
输入电压（范围） 6-20V
数字IO脚 14 (其中6路作为PWM输出）
模拟输入脚 6
IO脚直流电流 40 mA
Flash Memory 16 or 32 KB （其中2 KB 用于 bootloader）
SRAM 1 KB or 2 KB
EEPROM 0.5 KB or 1 KB （ATmega328）
CH340B USB转串口芯片
工作时钟 16 MHz
Type-C接口

3. How to make

3.1 Burn BootLoader

After the board is soldered, the board does not have a BootLoader at this time, which means that the board at this time cannot be used, and the BootLoader needs to be burned first.

3.1.1 First open the ISP routine

3.1.2 Wiring:

Connect Arduino UNO (which I believe every hardware engineer should have) and Arduino Nano (this example product) according to the following table,

3.1.3 Compile and upload the "Arduino as ISP" program to UNO

3.1.4 Start burning BootLoader

After completing 3.1.3, keep the connection between UNO and computer intact, and keep the connection between UNO and Nano intact;

Select Arduino Nano in the Arduino IDE tool, and select Old Bootloader for the processor. Use the old version of the boot (remain unchanged in any connection method).

Click to burn bootloader

Look at the command window below to see "avrdude done", that is, the BootLoader burning is completed.

3.2 Usage verification

Download the routine lighting code in the attachment, use Arduino IDE to compile and download it to the board, you can see the LED on the development board flashing.

void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}

4. Advantages

4.1 Change the USB micro to Type-C interface, which is more convenient for debugging programs.

4.2 Add a diode to prevent reverse connection of the power supply from burning the equipment.

4.3 Remove the ISP interface, compact, beautiful and elegant.