Sweet Pea Uno

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The SweetPea Uno+ is an Arduino Uno compatible board with an integrated NFC Tag chip with external antenna. This board allows you to to use your smart phone as a user interface towards it. An already implemented Arduino library and an example Android App demonstrates how to implement your user interface. Using the interface is as easy as holding your smart phone close to the NFC antenna, making your adjustments to the parameters and then writing the values back to the board.

The Board


As the image indicates the board has the standard Arduino Uno form factor. And although the only thing in common with the original Arduino Uno is the ATMega328P micro controller, the board is still fully Arduino Uno compatible. To lower costs and avoid infringing on Arduino intellectual property we are using another USB transceiver chip. In many of our designs we are using Silabs CP2104 which is a great low cost alternative to both FTDI and the ATMega solution that Arduino are using on their boards.

As mentioned earlier the Uno+ comes with an NFC (Near Field Communication) chip and antenna. This interface allows your smart phone to control parameters and features on the board.

Here's a short list on the features on the board.


  • J1 - I2C Connector. This is a SeeedStudio Grove compatible connector.
  • J2 - Serial Connector. This is also a SeeedStudio Grove compatible connector for serial comms.
  • J3 and J4 - Two One-Wire connector that can be used to create two domains of One-Wire networks.
  • J5 - NFC Antenna Connector. Here you can connect you NFC antenna. A simple PCB based antenna is supplied with the board.
  • J6 - Power Connector. A 5.5mm/2.1mm barrel connector used to connect a power supply with up to 12V.
  • J7 - Micro USB connector. Used to communicate with your PC.
  • And of course the standard Arduino connectors which are unlabeled.


5 LED's are available on the board with the following functions.

  • ON - Indicates that power has been applied, either from the USB connector (J7) or the power connector (J6).
  • L - This is the programmable LED connected to IO13.
  • RX1 and TX1 - Are connected to the datalines of the USB transceiver and indicate activity in respective direction.
  • ACT - USB Active indication. This indicates that there is a active USB connection between the host computer and the Uno+.

Reserved Pins

The NFC tag is connected to the on board I2C channel which effectively means that analog channels 4 - 5 are not available. If the NFC tag is not to be used these channels can again be used as analog inputs. However as they are pulled up by 4.7Kohm resistors you need to have an amplifier that drives these inputs to overcome the effect of the pull ups.


The SweetPea UnoNet+ board includes NFC technology that emulates an NFC tag, allowing a smart phone to read and write data, through NFC, to an EEPROM located on the board. Effectively this means that a simple application can act as the UI towards the UnoNet board. An on board U.FL. connector allows you to hook up any compatible NFC antenna to the it. The kit of course comes with an antenna that works perfectly with the board.

For the NFC Tag we have developed our own library that takes care of the reading and writing of records to the EEPROM memory. In read only mode this library consumes less than 3.5KByte of flash memory. The source code is available at Github.

We also designed a simple android app that will work with any of our NFC Tag enabled boards. Different boards will show different UI's and which can easily be modified to suit your own needs. This app can be used as it is or as a base for your own implementation. Oh yes, I willingly admit that it is not the worlds most beautiful app that has been written. The app is available on Google Play and as source code on Github.


This section contains useful files to be used with your Uno+.

Tips, Tricks and useful links

Nothing yet