I always wanted to track my house's power consumption and usage. I have an Efergy monitor but it doesn't have PC (USB|Serial) connection so I decided to try to get some information.
Hardware
Transmitter
The transmitter has three 3.5'' jacks for connecting one or three current clamps (monophase vs triphase).
It transmits current information every 6, 12 or 18seconds (configurable with push button)
I configured mine every 6 seconds to help with sniffing information
Receiver
RF Side
The wireless monitor uses an AMICCOM A7201A UHF receiver (SSOP20 package) working in hardware pin mode (SPI disabled)
It's configured as:
| Pin |
Name |
Value |
Comment |
| 13 |
SPIS |
Low |
Disable SPI -> Hardware Pin mode |
| 14 |
BAND |
High |
434 Mhz |
| 15 |
SPI_CLK |
Low |
Not used |
| 16 |
AFSK |
Low |
FSK |
Pin 18 shows a pulse train every 6 seconds.
The first pulses (~2.6 to ~3.8 msec) are variable and I assume is some sort of pseudo-random information to match transmitter with receiver. This pulse is variable and I've seen if ranging from ~1 to ~4 mseconds.
Then, at ~7,6 msec there's a long high pulse that leads the data start. At ~8.6 msec the actual data starts.
In the following graph, you can see the overlapped data start of 6 transmissions:
Each bit starts at each high to low transition.
The encoding for 1s is to have a >50% duty cycle for the bit.
The encoding for 0s is to have a <50% duty cycle for the bit.
In the next graph, you can see the whole data transfer. Red line shows bit times. Green lines show 1s (line present) or 0s (no line)
CPU Side
There's a microcontroller glued to the PCB but no information about brand/model. There are some hints about the Xtal location but nothing more....
Communication
Links
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