Computing stuff tied to the physical world

Picking up P1 data

In Hardware on Jan 1, 2013 at 00:01

Just in time for 2013, I hooked up the smart meter which was installed a month ago:


This connects DIO4 to the output of the P1 port, which has the following pinout:

Screen Shot 2012-12-31 at 11.25.43

The circuit is as follows:

JC's Grid, page 52

The request pin has to be pulled to 5V (it very likely just powers the isolated side of the built-in optocoupler). The 10 kΩ signal pull-up is needed to improve the rising flank of the signal, and the 10 kΩ resistor to the I/O pin prevents problems when the input signal rises above the 3.3V powering the ATmega.

Tomorrow, I’ll describe the software that goes along with this.