Computing stuff tied to the physical world

Home control shield

In AVR on Jan 22, 2009 at 16:37

The “home control” unit I mentioned recently was intended to have two shields, stacked as follows:


Unfortunately, the top shield with the I2C display turns out to either shield the underlying DCF77 receiver too much, or to generate too much interference, or both. So I’m going to leave it off:


As a result, this is just an Arduino Duemilanove with a “peripherals” proto-shield by Adafruit on top, containing:

  • an RFM12B 868 MHz radio module from HopeRF
  • a µSD socket with a 2 Gb card from Kingston
  • a DCF77 receiver from Pollin (

The resistors are used as level converters, since the SPI bus has to run at 3.3V. There’s also 3.3V regulator (look between the resistors and the pin header), because the µSD programming current can run up to 100 mA – more than the Arduino’s FTDI chip can supply.

All peripherals have been verified to work, separately as well as in combination.

So this unit now has all the pieces needed to log (and accurately timestamp) virtually unlimited amounts of data flying through RFM12B airspace… fully unattended, with just a USB or +9V power source.