File espos_sensor_math.h¶

FileList > espos_sensors > include > espos_sensor_math.h

#include <stdbool.h>
#include <stdint.h>

Public Functions¶

Type	Name
float	espos_adc_counts_to_volts (int raw, float full_scale_v, int max_counts) Raw ADC counts to volts, with no eFuse calibration available.
uint32_t	espos_counter_delta (int prev, int now, int limit) The number of edges between two readings of a counter that wraps at `limit` and restarts at zero.
float	espos_hz_to_revolutions (float hz, int pulses_per_rev) Revolutions per second from a pulse frequency and the pulses per revolution of the sender.
float	espos_pulses_to_hz (uint32_t count, uint64_t interval_us) Edges counted over a measured interval, as a frequency in Hz.

Public Functions Documentation¶

function espos_adc_counts_to_volts¶

Raw ADC counts to volts, with no eFuse calibration available.

float espos_adc_counts_to_volts (
    int raw,
    float full_scale_v,
    int max_counts
)

full_scale_v is the nominal full-scale voltage of the attenuation in use and max_counts the top of the range (4095 at 12 bits). Accurate to a few percent, which is the honest accuracy of an uncalibrated SAR ADC.

function espos_counter_delta¶

The number of edges between two readings of a counter that wraps at limit and restarts at zero.

uint32_t espos_counter_delta (
    int prev,
    int now,
    int limit
)

One wrap between calls is accounted for. More than one is indistinguishable from none the counter is 16-bit and carries no generation so a poll must be fast enough that fewer than limit edges arrive between two of them.

function espos_hz_to_revolutions¶

Revolutions per second from a pulse frequency and the pulses per revolution of the sender.

float espos_hz_to_revolutions (
    float hz,
    int pulses_per_rev
)

Signal K's propulsion.*.revolutions is per SECOND, not per minute: the single most common unit error on a tachometer, and one that looks plausible either way until someone compares it with the engine's own gauge.

function espos_pulses_to_hz¶

Edges counted over a measured interval, as a frequency in Hz.

float espos_pulses_to_hz (
    uint32_t count,
    uint64_t interval_us
)

The interval is measured rather than assumed: dividing by the nominal poll period assumes the poll ran on time, and the first poll after a reconnect or a flash erase is exactly when it did not. A zero interval returns 0 rather than dividing by it.

The documentation for this class was generated from the following file espos_sensors/include/espos_sensor_math.h