Arduino Mini comes without USB connection. To be able to connect it to computer, use USB - UART TTL converter.

To check your USB adapter:

  1. Wire USB adapter’s TX to it’s RX (this will make it recieve same data, which it transmitted).
  2. Plug USB into computer.
  3. In Arduino IDE, check Tools -> Port, and select propper (hopefuly) COM port.
  4. Open Serial Monitor, and type any string into input - you should recieve it back.
  5. If you don’t recieve data back - you might select wrong COM port, or you have mulfunction USB converter.

Wiring USB to Arduino

To communicate, Arduino and USB will use RX and TX pins. Both have them, and they must be connected as USB-TX to Arduino-RX and USB-RX to Arduino-TX. One of these pins is transmitter, another is reciever. That is why they are wired like this.

Power for Arduino can be connected to 5V and Gnd pins to corresponing pins of USB converter. These same pins can used to power other connected devices. This will work, because all these devices will be connected in parallel, and hence - will have same voltage (which is important).

You can use external power source (9V battery). In this case - you should plug battery’s + to Arduino Mini’s 9V marked pin. Gnd should be connected to same pin. Other devices should be powered from pin marked 5V, or 3.3V depending on there requirements.

Uploading Sketch

After connecting Arduino to computer, select propper port (see top of the chapter), and Tools -> Board. Changing board will force complete recompelation of your sketch. This might take some time.

To upload sketch - click Upload button in Arduino IDE, and SIMULTANEOUSLY press and hold Reset button on Arduino Mini board. As soon as upload process complete (green bar of compile/upload disappears) - release Reset button. You will see blue LEDs start flashing on your USB converter.

Upload complete! Sketch is already working.

External Powering

See wiring Arduino section for these details. Last passage explains powering from 9V battery. 5V can be used from external USB powering.

Read More

Uploading sketches on Aruino Mini.