Arduino mini Pro

My first Arduino board, an Arduino Uno, is fine but huge. So I looked for a more compact board: the Arduino Pro mini.

It has the same features and pins except the USB connection is apart. There's enough space into a fischertechnik 9V red box to pack 2 I2C connectors and 3 serial ports.

First drawings confirm it was possible to pack all on a 6 x 3 cm board. 

The USB to serial interface works fine. 

However, uploading a sketch onto the Arduino requires using the blue serial port (standard serial port on pins 0 and 1) and a 5th cable for automatic reset. Tests on prototype boards were conclusive.

After some soldering, final result is here, either on a red box or a yellow one.

Below, the IMU project: same features, smaller size! 

One I2C and one serial ports are used.

The compact Arduino has no regulator and thus requires external regulated voltage. 

When connected to I2C, 5V is provided as standard by the bus.

In other cases, an external 5V regulator is needed. So I built one.
The fischertechnik 9V battery could now supply the Arduino mini pro.

As an accessory, a micro-SD card reader to plug into one serial port.