This example is a Pro Mini clone with an 8 Mhz XTAL, 3V3 VREG and ATMEGA328P micro-controller.

    DTR TXD RXD VCC GND GND
        PD1 PD0
TXD PD1                     RAW
RXD PD0                     GND
RST                         RST
GND                         VCC
2   PD2         PC5 A5  PC3  A3
3   PD3         PC4 A4  PC2  A2
4   PD4                 PC1  A1
5   PD5                 PC0  A0
6   PD6                 PB5  13
7   PD7  LED    RESET   PB4  12
8   PB0  PB5    BUTTON  PB3  11
9   PB1                 PB2  10
                PC6 PC7
            GND A6  A7

A difference between this cheap clone and the original is it presents A6 and A7 on two extra pins.

We can power the board with VCC up to 5V or utilise the RAW input which will feed the 3V3 regulator.

A cp2104 serial module is well suited to connect to the pro mini and is able to supply both 3V5 and 5V for VCC. The photo, top right, shows a cp2104 module in the background.

An arduino boot loader is present on this device which communicates at 57600 baud. This is a reliable speed for a Pro Mini with an 8MHz XTAL.

In the arduino IDE, the device is selected as an `Arduino Pro or Pro Mini (3.3V, 8 MHz) w/ ATMEGA328'.

This device doesn't have an ISP connector but we can wire and replace the boot loader, for example, with a USBasp.

VDD
GND
RESET 
MISO  PB4
SCK   PB5
MOSI  PB3