AN2799

Firmware description

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4.1.1

Attributes

The object attributes are described as follows:

●

m_Voltage: “private” variable containing the last read voltage in mV

●

m_Current: “private” variable containing the last read current in mA

●

m_Energy: “private” variable containing the last read energy in mW

●

Registers: “public” structured variables containing the STPM01 registers:

–

DAP: type0 active energy

–

DRP: reactive energy

–

DSP: apparent energy

–

DFP: type1 energy

–

DEV: RMS values of measured voltage and current

–

DMV: instantaneous values of measured voltage and current

–

CFL: lower part of the configuration register

–

CFH: higher part of the configuration register

●

Signals: “public” structured variables containing the signals descriptor used to interface

STM32 with STPM01:

–

PM_SCS: this signal enables the SPI operation when low

–

PM_SYN: When SCS is low, this signal selects the read or write operation. When

both SCS and SYN signals are high, the results of the input or output data are

transferred to the transmission latches.

–

PM_SDA: SPI MISO signal. This signal is used as the STPM01 data signal. The

direction of this signal depends on the SYN signal.

–

PM_SCLK: SPI clock signal

Each signal descriptor contains the STM32 port and pin number. For further details about

SPM01 registers and the microcontroller interface, please refer to the STPM01 datasheet.

4.1.2

Methods

The object methods are implemented by means of pointers to functions which are described

as follows:

●

Create: this function initializes all power meter object elements (properties and

methods).

●

Destroy: not used. Implemented to have a general object implementation.

●

Init: this function initializes the power meter object properties and the power meter

signals putting them in the idle state.

●

Reset: this function executes the reset sequence to perform the “remote reset”

operation of the STPM01 (

Figure 4).

●

SetSignals: this function initializes the “signals” attribute of the power meter object and

configures the GPIOs related to the signals.

●

GetSignals: this function retrieves the “signals” attribute of the power meter object.

●

SetCfgRegMode: this function sets the STPM01 configuration register as shadow

latches or OTP. In current AN firmware the STPM01 is configured to use the shadow

latches for the configuration for testing reasons.