ESP-01 board is different from NodeMCU DevKit (ESP-12E) board. It doesn't have USB support. You need a USB to TTL serial converter and a certain circuit to switch the board between normal boot and flashing mode. You can buy a USB to TTL converter as cheap as $1 or you can utilize your current Arduino board. First, I want to show my simple circuit using a USB to TTL converter to flash ESP-01. I use Prolific USB to TTL. It's the cheapest device you can get in the market. If you use this device on Windows operating system, you must check Device Manager and validate that the device isn't in an error state. If it's an error, you can use the solution from HERE . The following image shows the circuit for flashing ESP-01 using a USB to TTL converter. I use an external 3.3V supply because my Prolific can provide only a 5V supply from USB and the current is too low. USB to TTL to ESP-01 If you are too lazy with push-button and resistor you can use the followin...