servo_sim.c File Reference

Single-servo and two-servo models of a control surface. More...

#include "servo_sim.h"
#include <string.h>

Functions
void	servo_sim_defaults (servo_sim_cfg_t *cfg)
	A standard servo on a well-set-up surface, binding at 1150 and 1880 us.
void	servo_sim_init (servo_sim_t *s, const servo_sim_cfg_t *cfg)
	Start the single-servo model at the middle of its stops.
static float	noise (servo_sim_t *s)
	Deterministic, so a failing case reproduces.
float	servo_sim_step (servo_sim_t *s, uint16_t cmd_us, uint32_t now_ms)
	Advance the model to now_ms with the servo commanded to cmd_us, and return the current its sensor would report.
void	servo_pair_defaults (servo_pair_cfg_t *cfg, uint16_t centre_us)
	Defaults for two servos on one surface.
void	servo_pair_init (servo_pair_t *p, const servo_pair_cfg_t *cfg)
	Start the two-servo model with both servos at the centre.
float	servo_pair_disagreement (const servo_pair_t *p, uint16_t cmd_a_us, uint16_t cmd_b_us)
	How far apart the two hold the surface, in microseconds. Hardware cannot report this; the search is blind to it and a test may read it.
static bool	approach (float *pos, float target, float reach)
	Move pos toward target by at most reach; true if it arrived.
float	servo_pair_step (servo_pair_t *p, uint16_t cmd_a_us, uint16_t cmd_b_us, uint32_t now_ms)
	Advance both servos to now_ms with the commands given, and return the total current the pair draws.

Detailed Description

Single-servo and two-servo models of a control surface.

SPDX-License-Identifier: MIT

Function Documentation

approach()

bool approach ( float * pos, float target, float reach )

static

Move pos toward target by at most reach; true if it arrived.

Parameters

pos	Position to move, us. Updated in place.
target	Target position, us.
reach	Largest move allowed, us.

Returns

true when the position equals the target after the move.

noise()

float noise ( servo_sim_t * s )

static

Deterministic, so a failing case reproduces.

Parameters

s	Model state. Advances the noise generator.

Returns

noise, A, within plus or minus half of noise_a.

servo_pair_defaults()

void servo_pair_defaults	(	servo_pair_cfg_t *	cfg,
		uint16_t	centre_us )

Defaults for two servos on one surface.

Parameters

cfg	Configuration to fill.
centre_us	Centre pulse width, us.

servo_pair_disagreement()

float servo_pair_disagreement	(	const servo_pair_t *	p,
		uint16_t	cmd_a_us,
		uint16_t	cmd_b_us )

How far apart the two hold the surface, in microseconds. Hardware cannot report this; the search is blind to it and a test may read it.

Parameters

p	Model state.
cmd_a_us	Commanded pulse width of servo A, us.
cmd_b_us	Commanded pulse width of servo B, us.

Returns

distance between the two servos on the surface, us; 0 when p is NULL.

servo_pair_init()

void servo_pair_init	(	servo_pair_t *	p,
		const servo_pair_cfg_t *	cfg )

Start the two-servo model with both servos at the centre.

Parameters

p	Model state to initialise.
cfg	Configuration to copy.

servo_pair_step()

float servo_pair_step	(	servo_pair_t *	p,
		uint16_t	cmd_a_us,
		uint16_t	cmd_b_us,
		uint32_t	now_ms )

Advance both servos to now_ms with the commands given, and return the total current the pair draws.

Both servos take time to arrive, which is why this takes a clock: a reading taken before they have arrived is a reading of two servos in transit, not of two servos disagreeing. The settle time separates the two.

Parameters

p	Model state.
cmd_a_us	Commanded pulse width of servo A, us.
cmd_b_us	Commanded pulse width of servo B, us.
now_ms	Current time, ms.

Returns

total current the pair draws, A; 0 when p is NULL.

servo_sim_defaults()

void servo_sim_defaults

(

servo_sim_cfg_t *

cfg

)

A standard servo on a well-set-up surface, binding at 1150 and 1880 us.

Parameters

cfg	Configuration to fill. Does nothing when NULL.

servo_sim_init()

void servo_sim_init	(	servo_sim_t *	s,
		const servo_sim_cfg_t *	cfg )

Start the single-servo model at the middle of its stops.

Parameters

s	Model state to initialise. Does nothing when NULL.
cfg	Configuration to copy. Does nothing when NULL.

servo_sim_step()

float servo_sim_step	(	servo_sim_t *	s,
		uint16_t	cmd_us,
		uint32_t	now_ms )

Advance the model to now_ms with the servo commanded to cmd_us, and return the current its sensor would report.

Parameters

s	Model state.
cmd_us	Commanded pulse width, us.
now_ms	Current time, ms.

Returns

current the sensor reports, A; 0 when s is NULL.