CH340E - USB-UART converter for 0.99USD
If you like arduino boards with ATmega328, SAMD21 or ESP8266, you need USB-UART converter with DTR pin. The DTR pin is needed for uploading of your code. DTR is connected to reset pin of microcontroller.
cnx-software share a news about very cheap and small USB-UART converter with DTR pin - CH340E.

The dimension of board is only 16x16mm, it contains microUSB connector and 6 pins (5V, 3.3V, GND, TX, RX a DTR). Everything what you need for your programming.

The communication speed is tested up to 150 000 Bd.

You can buy the board on

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