Data Acquisition

Data Acquisition (DAQ)

Measurements are taken using ADC with DMA. The DAC is used to generate reference voltages for bi-directional current measurement. Data is stored in structs, which are afterwards used by the control algorithms

All calculations assume a 16-bit ADC, even though the STM32 ADCs natively support 12-bit. Using 16-bit for calculation allows to increase resolution by oversampling. Left-aligned 12-bit ADC readings can be treated as 16-bit ADC readings.

Enums

enum [anonymous]

Values:

enumerator DT_FOREACH_CHILD

Functions

static inline float adc_raw_to_voltage(int32_t raw, int32_t vref_mV)

Convert 16-bit raw ADC reading to voltage

Parameters:

  • raw – 16-bit ADC reading

  • vref_mV – Reference voltage in millivolts

Returns:

Voltage in volts

static inline int32_t adc_voltage_to_raw(float voltage, int32_t vref_mV)

Convert voltage to 16-bit raw ADC reading

Parameters:

  • voltage – Voltage in volts

  • vref_mV – Reference voltage in millivolts

Returns:

16-bit ADC reading

void calibrate_current_sensors(void)

Set offset vs. actual measured value, i.e. sets zero current point.

All input/output switches and consumers should be switched off before calling this function

void daq_update(void)

Updates structures with data read from ADC

void daq_setup(void)

Initializes ADC, DAC and DMA

void adc_update_value(unsigned int pos)

Read, filter and check raw ADC readings stored by DMA controller

void daq_set_lv_limits(float lv_overvoltage, float lv_undervoltage)

Set lv side (battery) voltage limits where an alert should be triggered

Parameters:

  • lv_overvoltage – Upper voltage limit

  • lv_undervoltage – Lower voltage limit

void daq_set_hv_limit(float hv_overvoltage)

Set hv side (grid/solar) voltage limit where an alert should be triggered

Parameters:

hv_overvoltage – Upper voltage limit

void adc_upper_alert_inhibit(int adc_pos, int timeout_ms)

Add an inhibit delay to the alerts to disable it temporarily

Parameters:

  • adc_pos – The position of the ADC measurement channel

  • timeout_ms – Timeout in milliseconds

struct AdcAlert
#include <daq.h>

Struct to define upper and lower limit alerts for any ADC channel

Public Members

void (*callback)()

Function to be called when limits are exceeded.

uint16_t limit

ADC reading for lower limit.

int16_t debounce_ms

Milliseconds delay for triggering alert.