Friday 11 November 2011

Calunium: PCB version

Calunium. Click on the image for an annotated version.

Calunium is an Arduino clone based on the ATmega1284 microcontroller. Initially a strip board design was created to test the concept. Following the success of the strip board version I decided to create a PCB version. Initially I hoped to include Wifi networking, an SD card and a real-time clock. It soon became apparent that including this many peripherals was not possible with the desired footprint using the free version of Cadsoft Eagle. The final version includes a real-time clock. Wifi networking (using the Roving Networks XV Wifi module) and storage using an SD card is provided by a shield designed specifically for Calunium. The RN-XV/SD shield will be described in a future blog post. The pin mapping of the PCB differs slightly from the strip board version; the Arduino software takes care of the differences provided the correct board type is selected.

  • Shield-compatible with Arduino Uno, with extra I/O laid out to be compatible with Arduino Mega pins. Pin mapping is chosen for maximum compatibility with Uno.
  • I2C (SDA/SCL) mapped to standard location as used by Arduino Mega but jumpers can be used to replace A4/A5 with SDA/SCL signals for compatibility with Arduino Uno.
  • Second UART (D1,D2) signals also mapped to corresponding location on Arduino Mega (TX1,RX1).
  • ISP header in standard location, allowing the Arduino ethernet/SD shield to be used.
  • D13 LED connected via FET to avoid loading D13.
  • Direct USB interface using V-USB, for firmware updates without requiring FTDI cable. Can be disabled by removing jumpers. Not yet tested.
  • Real-time clock (DS1307). Output square wave can be routed to D6 (INT2) or D15 (TOSC1, for input to timer/counter 2). Use either CR2032 or CR1220 battery depending upon battery holder fitted.
  • Power from USB or FTDI connector.
  • Switches, jumpers, connectors and USB socket outside of the standard Arduino shield footprint so they do not interfere with shields and are accessible when shields are fitted.
  • Auxiliary power connector; connect your own voltage regulator or boost converter. 5V from USB (FTDI and/or USB connector) and 3V from RTC battery also available on the connector. 3.3V operation is also possible.
  • Auto-reset can be disabled by removing jumper.
  • Pads to fit LM61 temperature sensor.
  • Usable PCB-mounting holes.
  • JTAG header for debugging/programming.
  • Eagle PCB design files available under Creative Commons Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0 licence.
  • Arduino files for Calunium are available on Github.