This example is a clone with a CH340G USB UART.

These clones are very cheap and are nano 3.0 compatible with an ATMEGA328P micro-controller and 16 MHz XTAL.

               +--------------+
               |   5 3 1 ISP  |
               |   6 4 2      |
               |  RX TX PW L  |
D1 TX         1|   PD0        |30 VIN
D0 RX         2|   PD1        |29 GND
RESET         3|     RESET    |28 RESET
GND           4|              |27 5V
D2 INT0       5|   PD2 ADC7   |26 A7
D3 INT1       6|   PD3 ADC6   |25 A6
D4            7|   PD4 PC5    |24 A5 SCL
D5            8|   PD5 PC4    |23 A4 SDA
D6            9|   PD6 PC3    |22 A3
D7           10|   PD7 PC2    |21 A2
D8           11|   PB0 PC1    |20 A1
D9           12|   PB1 PC0    |19 A0
D10 SS       13|   PB2        |18 AREF
D11 MOSI     14|   PB3        |17 3V3
D12 MISO     15|   PB4 PB5    |16 D13 LED SCK
               +--------------+

This device is either powered from the USB bus of from VIN which feeds a 5V LDO regulator.

The V3 pin on the CH340G (4) is used to generate the external 3V3 power on pin 17. Chip documentation suggests that this pin was not designed for this task and its maximum current capability is unknown.

Communications is via the built-in CH340G usb to serial bridge. This device can achieve 115200 baud.

An arduino boot loader is present on this device by default running at 57600 baud. Installation of Optiboot is recommended to increase this speed to 115200.

A 6-pin ATMEL ISP header is present. This will require an ISP adapter for the USBasp.

D12 MISO PB4 |1 2| VDD
D13 SCK  PB5 |3 4| D11 MOSI PB3
RESET        |5 6| GND