unit_SPA06_data.hpp File Reference

SPA06-003 measurement data + calibration/compensation (framework independent) More...

#include <array>
#include <cstdint>
#include <cmath>
#include <limits>

Go to the source code of this file.

Classes
struct	m5::unit::spa06::coeffs_t
	Factory calibration coefficients (all 2's complement, already sign-extended) More...
struct	m5::unit::spa06::Data
	One SPA06 sample: a 6-byte burst from PSR_B2 (0x00) = PSR(24) + TMP(24), big-endian. More...

Namespaces
namespace	m5
	Top level namespace of M5Stack.

Enumerations
enum class	m5::unit::spa06::Oversampling : uint8_t {   X1 , X2 , X4 , X8 ,   X16 , X32 , X64 , X128 }
	Oversampling factor; the enum value is the PM_PRC/TM_PRC nibble (datasheet Table 4) More...
enum class	m5::unit::spa06::Rate : uint8_t {   Rate1 , Rate2 , Rate4 , Rate8 ,   Rate16 , Rate32 , Rate64 , Rate128 }
	Measurement rate; the enum value is the PM_RATE/TMP_RATE nibble (measurements per second) More...
enum class	m5::unit::spa06::Mode : uint8_t { Pressure = 0x05 , Temperature = 0x06 , PressureAndTemperature = 0x07 }
	Continuous measurement type; the enum value is the MEAS_CFG MEAS_CTRL[2:0] background-mode code. More...

Functions
float	m5::unit::spa06::scale_factor (const Oversampling oversampling)
	Compensation scale factor kP/kT for an oversampling rate (datasheet Table 4)
uint32_t	m5::unit::spa06::measurement_time_x10 (const Oversampling oversampling)
	Measurement time (ms x10) for an oversampling rate (datasheet Table 8), indexed by nibble.
bool	m5::unit::spa06::valid_combination (const Oversampling osrs_p, const Oversampling osrs_t, const Rate rate, const Mode mode)
	True if a rate/oversampling/mode combination fits the datasheet timing budget.
int32_t	m5::unit::spa06::sign_extend (const uint32_t v, const uint8_t bits)
	Sign-extend the low bits of v (2's complement)
coeffs_t	m5::unit::spa06::parse_coeffs (const std::array< uint8_t, 21 > &r)
	Parse the 21 COEF register bytes (0x10..0x24) into coeffs_t (datasheet Table 10)
float	m5::unit::spa06::compensate_temperature (const int32_t tmp_raw, const coeffs_t &c, const float kt)
	Compensated temperature (degC) from a raw TMP reading and scale kT.
float	m5::unit::spa06::compensate_pressure (const int32_t psr_raw, const int32_t tmp_raw, const coeffs_t &c, const float kp, const float kt)
	Compensated pressure (Pa) from raw PSR/TMP readings and scales kP/kT (datasheet 4.6.1)
float	m5::unit::spa06::altitude_m (const float pressure_hpa, const float sea_level_hpa)
	Relative altitude (m) from a pressure and a reference (both hPa), barometric formula.

Variables
constexpr int32_t	m5::unit::spa06::NOT_MEASURED {-8388608}
	Sentinel value of psr_raw()/tmp_raw() for a register not measured yet (reset value 0x800000)

Detailed Description

SPA06-003 measurement data + calibration/compensation (framework independent)

PSR/TMP are 24-bit 2's complement; 11 calibration coefficients (c0,c1 12-bit; c00,c10 20-bit; c01,c11,c20,c21,c30 16-bit; c31,c40 12-bit) drive a high-order compensation polynomial. Pressure is returned in Pa; the UnitSPA06 driver converts to hPa.

Enumeration Type Documentation

Mode

enum class m5::unit::spa06::Mode : uint8_t

strong

Continuous measurement type; the enum value is the MEAS_CFG MEAS_CTRL[2:0] background-mode code.

Enumerator
Pressure	Continuous pressure only (temperature() returns NaN)
Temperature	Continuous temperature only (pressure() returns NaN)
PressureAndTemperature	Continuous pressure and temperature (both valid)

Oversampling

enum class m5::unit::spa06::Oversampling : uint8_t

strong

Oversampling factor; the enum value is the PM_PRC/TM_PRC nibble (datasheet Table 4)

Enumerator
X1	x1 (single, lowest precision)
X2	x2
X4	x4
X8	x8
X16	x16 (standard)
X32	x32
X64	x64
X128	x128 (highest precision)

Rate

enum class m5::unit::spa06::Rate : uint8_t

strong

Measurement rate; the enum value is the PM_RATE/TMP_RATE nibble (measurements per second)

Enumerator
Rate1	1 measurement/s
Rate2	2 measurements/s
Rate4	4 measurements/s
Rate8	8 measurements/s
Rate16	16 measurements/s
Rate32	32 measurements/s
Rate64	64 measurements/s
Rate128	128 measurements/s

Function Documentation

valid_combination()

bool m5::unit::spa06::valid_combination ( const Oversampling osrs_p, const Oversampling osrs_t, const Rate rate, const Mode mode )

inline

True if a rate/oversampling/mode combination fits the datasheet timing budget.

Background mode shares a 1-second timeline between pressure and temperature (single ADC). The active measurement type(s) must fit: Rate x (sum of active measurement times) < 1 second (datasheet 7.3 Note under Table 9). Pressure and temperature run at the same Rate in this driver.