[Tisham Dhar] has been interested in monitoring AC power and previously built a breakout board for the ADE7763. He wanted to find something cheaper and more modern. The ATM90E26 fit the bill. It can communicate via a UART or SPI, and has multiple metering modes. The problem? The evaluation module from Atmel costs about $500 (and for [Dhar] $800 Australian), although the part itself can be had for under a buck in bulk. (Atmel even sent him three samples for free.)
[Dhar] put the low voltage components from the reference design on a PCB and pocketed the difference in cost. So far, he’s tested the setup with a Teensy and low voltage measurements only. He plans to do a full test soon.
The test setup uses SPI mode 3 to talk to the processor. You can find the relevant code on GitHub.