Two examples of Pro Mini clones, one with an 8 Mhz XTAL and 3V3 VREG and the other with a 16 Mhz XTAL. and 5V VREG. Both have an ATMEGA328P micro-controller.

3V3 8 Mhz
=========
    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

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