The arduSTAMP is a small compact breadboard-friendly board  based on the ATmega328p with a USB to serial interface. It has more or less the same functionality of the Arduino, but in a small and compact package. It only lacks a voltage regulator, and works with a Mini-B USB. The USB interface can be detached from the board to have a 25mm x 25mm (1" x 1") fully operational ATmega328p. The board only has components on one side, making it ideal for assembly (hand solder, home reflow oven or skillet). The board is fully compatible with the Arduino software development environment. 
The detachable USB to serial interface that can be used standalone to interface to other projects. The pin-out of the USB to serial interface is compatible with the FTDI basic from sparkFun and can also be used with the Arduino Mini Pro, arduSTICK and arduCHIP. Essentially you get two products for the price of one.

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MicrocontrollerAtmel ATmega328p
Operating Voltage (logic level)1.8V to 5.5V  
Input Voltage range4.5V to 5.5 V
Input Voltage (limits)1.8V - 6 V
Digital I/O Pins14 (of which 6 provide PWM output) + 7 if analog inputs are not used
Analog Input Pins8
DC Current per I/O Pin (max)40 mA (200mA max when using all pins)
Flash Memory32 KB of which 2 KB used by boot loader, 1KB used by Adaboot (opt)
Clock Speed16 MHz (for Input Voltage range and when powered from USB)
Dimensions25mm x 50mm (1" x 2"), USB breakout (25mm x 25mm - 1" x 1"), Processor (25mm x 25mm) 


The arduSTAMP can be powered via the Mini-B USB connection connected to a computer or a 4.5-5.5V regulated external power supply (pins marked as +5V). The power source is automatically selected to the highest voltage source should both sources be connected to the board at the same time.
The FTDI FT232RL chip of the USB serial interface is only powered if the board is being powered over USB.
Board Layout
arduSTAMP Rev A.2 - Board Layout
The arduSTAMP is a small footprint Arduino compatible board. The Stamp has 3 main areas, the Main Board where the ATMega328 is with connectors exposing all the PINs from the chip. An on-board USB to serial interface and an ISP, which is only used to download the bootloader.
Each individual board can be cut out from the main PCB resulting in two separate products:
  • USB: this break out provides USB to serial interface. The PIN out is compatible with the FTDI basic breakout board from Sparkfun and the Arduino Mini Pro.
  • Main Board: this is a 25mm x 25mm (1" x 1") breakout board with all the pins exposed.  It can be regarded as a barebones Arduino.
The arduSTAMP is intended for prototyping, using the USB to serial interface to download your project binaries and debug them. Once the project is completed, remove or leave the USB to serial interface and connect it as a semi-permanent installation in objects. The board comes without pre-mounted headers (only the ISP header in mounted).
As the board only has components on one side it can be used as an SMD component of another board.
Input Output
arduSTAMP Rev A.1 - IO mapping
All the digital IO pins can be used as digital IOs using. Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. We recommend using the image above to map the functionality. 
Some of the pin of the arduSTAMP have specialized functions:

  • Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data. These pins are connected to the USB to serial interface on the USB breakout board.
  • External Interrupts: Digital pins 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. 
  • PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output.
  • SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication.
  • Analog Inputs: has 8 analog inputs, each of which provide 10 bits of resolution (i.e. 1024 different values). By default they measure from Vin to GND (regulated input of the board) and analogReference can be changed.
  • I2C: Analog Pin 4 (SDA) and Analog Pin 5 (SCL). Support I2C (TWI) communication using the Wire library.

  • AREF.: Analog reference voltage for the analog inputs.

  • RST.: Bring this line LOW to reset the microcontroller. This pin is connected between the reset line of the ATMega328 and the DTR control line of the FT232RL. This allows to the FT232RL to reset the chip prior to an upload. The board also has a reset button. When the main board is separated from the USB to serial interface the RST pin can be used to remotely reset to board.
The arduSTAMP provides a basic UART TTL serial communication interface, available on digital IO 0 (RX) and 1 (TX). In addition, to communicate with a computer, it has a USB to serial interface built in.
The Main Board also supports I2C (TWI) and SPI communication.
The arduSTAMP can be programmed with the Arduino software (download). For details, see the reference and tutorialsIt comes with a pre-programmed bootloader that communicates with the host computer using the original STK500 protocol.

arduSTAMP Rev A.2 - Component Placement
Boards can be ordered as a bare board with no components, as kits (boards and components separately) or fully assembled.
The assembly of the board is very easy as it only has components on one side, ideal for hobbyists enabling easy hand, reflow oven or skillet soldering.

Schematic and Design Files
arduSTAMP vA.1: schematic and eagle files.

Creative Commons License
arduSTAMP by F. Malpartida is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Based on a work at