esphome-emporia-vue-utility/docs/protocol-meter-reading.md

Meter Reading

There are at least two known response payloads sent by the MGM111 chip. MGM Firmware version 2 sends a 152 byte payload while version 7 sends a 44 byte payload. Check the section below relevant to your version.

Payload for Version 2

The meter reading response contains 152 bytes of payload, most of which seem to always be zeros. The fields in the payload have a mix of sizes and just to make things more confusing, the use of LSB / MSB byte ordering is inconsistent.
The below table details the payload format that's been reversed engineered so far. Blank cells have never been seen to be anything other than zero. Note the table is zero-indexed (starts at byte zero, not byte 1)

	0	1	2	3
0
4	EnergyVal
...
44				MeterDiv
48			EnergyCostUnit
52	Unknown 1
56		PowerVal
...
148	MeterTS

Known Fields

EnergyVal

Bytes 4 to 8, 32 bit int, unknown if signed, MSB

Energy Meter totalizer in watts, in other words, cumulative watt-hours consumed. Unknown when this value resets to zero, might reset monthly or on start of new billing cycle.

Sometimes, an invalid number greater than 0x00400000 is returned, it is not understood when or why this happens.

MeterDiv

At least byte 47, maybe as large as bytes 44 to 47

Some meters report values not in watts and watt hours but in a multiple of those values. EnergyVal and PowerVal should be divided by MeterDiv to determine the real value. Usually this is 1, but have also seen a value of 3.

EnergyCostUnit

Bytes 50 and 51 MSB(?)

Usually 0x03E8, which is 1000. Theorized to be how many EvergyVal units per "cost unit" (a value we don't appear to have). Since people are typically charged per kWh, this value is typically 1000.

This value is not currently used in the code

PowerVal

Bytes 57 to 59 (24 bit signed int, MSB)

The power being consumed at the moment in Watts. If you have a grid-tie solar / wind / battery system, then this value can go negative. Negative values are returned in 1's complement notation (if left most bit is 1, then flip all the bits then multiply by -1)

"Data Missing" / "Unknown" is denoted as max negative, 0x800000

MeterTS

Bytes 148 to 151 (32 bit unsigned int, LSB)

Number of milliseconds since an unknown event. Could be time since EnergyVal was reset, or could just be a free-running timer. Will roll over every 49 days.

Only reported as a debugging value, not used in calculations.

Unknown 1

Bytes 52 and 53

The meaning of the values in these fields is completely unknown. They appear to be static for each meter. Some of the observed values from users include:

fbfb
2c2b
3133

Random uneducated guess is that this is a bit field with flags about the meter configuration.

Payload for Version 7

The meter reading response contains 44 bytes of payload, most of which seem to always be zeros. The table below details the payload format that's been reversed engineered so far. Blank cells have never been seen to be anything other than zero. Some cells have hex codes that I have never seen change, but might differ for you. Note the table is zero-indexed (starts at byte zero, not byte 1).

	0	1	2	3
0	0x18	Incrementor	0x01
4			0x25	ImportWh~
8	~ImportWh
12		0x01
16	0x25	ExportWh~
20	~ExportWh			0x01
24	0x03		0x22	MeterDiv
28			0x02	0x03
32		0x22	EnergyCostUnit
36			0x04
40	0x2A	PowerVal

Known Fields

ImportWh

Bytes 7 to 10, (32 bit int, probably unsigned, LSB)

Cumulative watt-hours consumed from the grid. Unknown when the value resets, but probably never resets since ESP32 never sends a clock sync to the MGM111 so it likely just rolls over.

ExportWh

Bytes 17 to 20, (32 bit int, probably unsigned, LSB)

Cumulative watt-hours sent to the grid. Unknown when the value resets, but probably never resets since ESP32 never sends a clock sync to the MGM111 so it likely just rolls over.

MeterDiv

Byte 27

Used in conjunction with EnergyCostUnit and PowerVal to calculate the actual wattage.

EnergyCostUnit

Bytes 34 and 35 LSB

Usually 0xE803, which is 0x03E8 = 1000. Continuing the V2 theorization that this is the number of watt-hour units per "cost unit". Since people are typically charged per kWh, this value is typically 1000.

PowerVal

Bytes 41 and 43 (24 bit signed int, LSB)

The power being sent or consumed at this moment. The actual wattage is calculated with the formula:

Watts = PowerVal * MeterDiv / (EnergyCostUnit / 1000)

Incrementor

Byte 1 (8 bit unsigned int)

This just increments by 1 on each reading and rolls over.