Hello,
I’m designing an application to measure active and reactive power with BB (https://groups.google.com/d/msg/beagleboard/O5e6qS4qmYo/aG0leY4C-A0J ). I have finished the draft of my design and I’m attaching it to this message. I’m using Analog Devices ADE7753 chip, and SPI0 to communicate with our board.
I have still have some doubts:
- First of all, I’m powering BB from this circuit (using a 7805CKCT, 1.5 A to regulate +5V), and with the same signal I’m powering ADE7753. Could this be dangerous if ADE7753 wakes up too fast?
- I’m connecting directly SPI outputs from BB (3.3V) to ADE7753 (5V). On the other direction, I’m connecting SPI output from ADE7753 to BB via a simple resistor divider to get 3.3. v . Is there any problem with this setup to work?
- Is there any kind of danger when connecting the BB to the rest of my LAN even if I’m using a transformer isolating from 220VAC and I’m not connecting Neutral line?
The circuit is not complicated at all, and I’m sure my doubts are easy for anyone with more experience in connecting BB to external sources. This is my first try and any advice is welcome before I plug it all 
Thanks in advance
bb energy meter.pdf (55.2 KB)