use trim values to set mixer:scaler.offset

clamp mixer output offset to [-.2,.2] ([-2000, 2000] in mixer file)

add 8 main PWM trim parameters

add long desc to parameters and bump minor parameter version

src/modules/systemlib/mixer/mixer.h

@@ -192,6 +192,7 @@ public:
 	 */
 	virtual void 			set_max_delta_out_once(float delta_out_max) {};
 
+	virtual unsigned set_trim(float trim) = 0;
 
 protected:
 	/** client-supplied callback used when fetching control values */
@@ -333,6 +334,17 @@ public:
 	 */
 	virtual void 			set_max_delta_out_once(float delta_out_max);
 
+	/*
+	 * Invoke the set_offset method of each mixer in the group
+	 * for each value in page r_page_servo_control_trim
+	 */
+	unsigned set_trims(uint16_t *v, unsigned n);
+
+	unsigned set_trim(float trim)
+	{
+		return 0;
+	}
+
 private:
 	Mixer				*_first;	/**< linked list of mixers */
 
@@ -369,6 +381,12 @@ public:
 
 	virtual unsigned		mix(float *outputs, unsigned space, uint16_t *status_reg);
 	virtual void			groups_required(uint32_t &groups);
+	virtual void 			set_offset(float trim) {};
+	unsigned set_trim(float trim)
+	{
+		return 0;
+	}
+
 };
 
 /**
@@ -445,6 +463,8 @@ public:
 	 */
 	int				check();
 
+	unsigned set_trim(float trim);
+
 protected:
 
 private:
@@ -551,6 +571,11 @@ public:
 	 */
 	virtual void 			set_max_delta_out_once(float delta_out_max) {_delta_out_max = delta_out_max;}
 
+	unsigned set_trim(float trim)
+	{
+		return _rotor_count;
+	}
+
 private:
 	float				_roll_scale;
 	float				_pitch_scale;

src/modules/systemlib/mixer/mixer_group.cpp

@@ -112,6 +112,28 @@ MixerGroup::mix(float *outputs, unsigned space, uint16_t *status_reg)
 	return index;
 }
 
+unsigned
+MixerGroup::set_trims(uint16_t *values, unsigned n)
+{
+	Mixer	*mixer = _first;
+	unsigned index = 0;
+
+	while ((mixer != nullptr) && (index < n)) {
+		/* hardwired assumption that PWM output range is [1000, 2000] usec */
+		float offset = ((float)values[index] - 1500) / 500;
+
+		/* to be safe, clamp offset to range of [-100, 100] usec */
+		if (offset < -0.2f) { offset = -0.2f; }
+
+		if (offset >  0.2f) { offset =  0.2f; }
+
+		index += mixer->set_trim(offset);
+		mixer = mixer->_next;
+	}
+
+	return index;
+}
+
 unsigned
 MixerGroup::count()
 {

src/modules/systemlib/mixer/mixer_simple.cpp

@@ -72,6 +72,12 @@ SimpleMixer::~SimpleMixer()
 	}
 }
 
+unsigned SimpleMixer::set_trim(float trim)
+{
+	_pinfo->output_scaler.offset = trim;
+	return 1;
+}
+
 int
 SimpleMixer::parse_output_scaler(const char *buf, unsigned &buflen, mixer_scaler_s &scaler)
 {

src/modules/systemlib/pwm_limit/pwm_limit.c

@@ -206,15 +206,15 @@ void pwm_limit_calc(const bool armed, const bool pre_armed, const unsigned num_c
 				control_value = -1.0f * control_value;
 			}
 
-			if (trim_pwm[i] == 0) {
-				effective_pwm[i] = control_value * (max_pwm[i] - min_pwm[i]) / 2 + (max_pwm[i] + min_pwm[i]) / 2;
+//			if (trim_pwm[i] == 0) {
+			effective_pwm[i] = control_value * (max_pwm[i] - min_pwm[i]) / 2 + (max_pwm[i] + min_pwm[i]) / 2;
 
-			} else if (control_value < 0) {
-				effective_pwm[i] = control_value * (trim_pwm[i] - min_pwm[i]) + trim_pwm[i];
-
-			} else {
-				effective_pwm[i] = control_value * (max_pwm[i] - trim_pwm[i]) + trim_pwm[i];
-			}
+//			} else if (control_value < 0) {
+//				effective_pwm[i] = control_value * (trim_pwm[i] - min_pwm[i]) + trim_pwm[i];
+//
+//			} else {
+//				effective_pwm[i] = control_value * (max_pwm[i] - trim_pwm[i]) + trim_pwm[i];
+//			}
 
 			/* last line of defense against invalid inputs */
 			if (effective_pwm[i] < min_pwm[i]) {