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document DDM100TC connection

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King Kévin 2017-01-22 15:39:48 +01:00
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README.md
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@ -44,6 +44,24 @@ RTC
The onboard Real Time Clock (RTC) is used to track the uptime a periodically start querying all electricity meter for their measurement value.
The time interval between the periodic queries is hard coded in `main.c`.
By connecting a (coin cell) battery to VBAT the RTC keeps running, even if the board is not powered anymore.
DDM100TC
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This 3-phase 4-wire electricity meter provides an S0 interface.
On my model this would output 1600 impulse/kWh, thus each impulse corresponds to a power consumption of 0.625 Wh).
To record these impulses a timer input capture is used.
The number of impulses determines the energy used.
It is stored in a backup register, keeping the value in memory even when the board is powered down as long as a (coin cell) battery is connected to VBAT.
The interval between impulses allow to calculate the current power consumption.
The time has a resolution of 0.91 ms (leading to a power calculation error of <1%).
Connections DDM100TC <-> board:
- S0+, pin 8; +3.3V or +5V
- S0-, pin 7; TIM4_CH1, PB6 (use pull-down resistor)
ESP8266
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