From e45fe924520ec4ee1463f9402a4506ade5743700 Mon Sep 17 00:00:00 2001
From: Michael Buesch <mb@bu3sch.de>
Date: Sat, 21 Nov 2009 21:46:36 +0100
Subject: pressure_control: ADC averaging

Signed-off-by: Michael Buesch <mb@bu3sch.de>
---
 pressure_control/firmware/main.c   | 27 +++++++++++++++++++--------
 pressure_control/firmware/main.h   |  6 ++++--
 pressure_control/firmware/sensor.c |  6 ++++++
 pressure_control/firmware/sensor.h |  1 +
 4 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/pressure_control/firmware/main.c b/pressure_control/firmware/main.c
index 9f6cdd9..d39008d 100644
--- a/pressure_control/firmware/main.c
+++ b/pressure_control/firmware/main.c
@@ -60,6 +60,10 @@ static DEFINE_SENSOR(xy_control_sensor, (1<<MUX0), 245, 4400, 10000);
 #define Z_MAX_PRESSURE		1500
 #define Z_MAX_HYSTERESIS	300
 
+/* Report hysteresis (in mBar).
+ * Don't report changes lower than this (With some exceptions). */
+#define REPORT_HYSTERESIS	25
+
 
 
 /* EEPROM contents */
@@ -142,11 +146,17 @@ void get_pressure_state(struct pressure_state *ret)
  * Called in IRQ context. */
 void sensor_result(struct sensor *s, uint16_t mbar)
 {
-	/* Defer processing of the value to the mainloop, so we can do it with
-	 * interrupts enabled. */
-	state.measured_mbar = mbar;
-	mb();
-	state.needs_checking = 1;
+	state.measured_mbar += mbar;
+
+	if (++state.nr_adc_measurements >= 8) {
+		state.nr_adc_measurements = 0;
+		state.measured_mbar /= 8;
+		mb();
+		/* Defer processing of the value to the mainloop, so we can
+		 * do it with interrupts enabled. */
+		state.needs_checking = 1;
+	} else
+		sensor_retrigger();
 }
 
 jiffies_t get_jiffies(void)
@@ -206,7 +216,7 @@ static void do_check_pressure(struct valves *valves,
 			 * keep on doing this to reach the desired center value
 			 * more closely. */
 		} else {
-			/* We're within half the hysteresis.
+			/* We're within quarter of the hysteresis.
 			 * The pressure is OK. Make sure the valves are
 			 * all idle. */
 			report_change = (cur_state != VALVES_IDLE);
@@ -222,7 +232,7 @@ static void do_check_pressure(struct valves *valves,
 			valves_disarm_auto_idle(valves);
 		}
 	}
-	if (abs((int32_t)mbar - (int32_t)(*reported_mbar)) >= 40)
+	if (abs((int32_t)mbar - (int32_t)(*reported_mbar)) >= REPORT_HYSTERESIS)
 		report_change = 1;
 	if (report_change) {
 		remote_pressure_change_notification(state.measured_mbar_xy,
@@ -334,7 +344,7 @@ int main(void)
 			if (++sensor_cycle == __NR_SENSOR_CYCLE)
 				sensor_cycle = 0;
 			state.needs_checking = 0;
-			next_sensor_trigger = now + msec_to_jiffies(20);
+			next_sensor_trigger = now + msec_to_jiffies(5);
 			mb();
 			need_sensor_trigger = 1;
 		}
@@ -343,6 +353,7 @@ int main(void)
 			/* It's time for triggering another
 			 * sensor measurement. */
 			need_sensor_trigger = 0;
+			state.measured_mbar = 0;
 			switch (sensor_cycle) {
 			case SENSOR_CYCLE_XY:
 				sensor_trigger_read(&xy_control_sensor);
diff --git a/pressure_control/firmware/main.h b/pressure_control/firmware/main.h
index b229ade..915e66e 100644
--- a/pressure_control/firmware/main.h
+++ b/pressure_control/firmware/main.h
@@ -44,10 +44,10 @@ struct pressure_config {
 struct pressure_state {
 	/* Sensing and adjustment logic enabled? */
 	bool device_enabled;
-	/* The last measured pressure (in mBar).
+	/* The sum of the last measured pressures (in mBar).
 	 * It depends on sensor_cycle which valves this
 	 * value belongs to. */
-	uint16_t measured_mbar;
+	uint32_t measured_mbar;
 	/* The current pressure for the individual valves */
 	uint16_t measured_mbar_xy;
 	uint16_t measured_mbar_z;
@@ -57,6 +57,8 @@ struct pressure_state {
 	/* True, if the current pressure value needs checking against
 	 * the desired pressure config. */
 	bool needs_checking;
+	/* The current count of lowlevel ADC measurements. */
+	uint8_t nr_adc_measurements;
 };
 
 void get_pressure_config(struct pressure_config *xy,
diff --git a/pressure_control/firmware/sensor.c b/pressure_control/firmware/sensor.c
index 08eca77..6e59bb1 100644
--- a/pressure_control/firmware/sensor.c
+++ b/pressure_control/firmware/sensor.c
@@ -72,6 +72,12 @@ void sensor_trigger_read(struct sensor *s)
 	adc_trigger(s->adc_mux, 1);
 }
 
+void sensor_retrigger(void)
+{
+	/* Retrigger an ADC conversion on the currently active sensor. */
+	adc_trigger(active_sensor->adc_mux, 1);
+}
+
 void sensor_init(struct sensor *s)
 {
 	mdelay(20); /* Warm-up time */
diff --git a/pressure_control/firmware/sensor.h b/pressure_control/firmware/sensor.h
index 8f3c4e5..73b0835 100644
--- a/pressure_control/firmware/sensor.h
+++ b/pressure_control/firmware/sensor.h
@@ -27,6 +27,7 @@ struct sensor {
 	}
 
 void sensor_trigger_read(struct sensor *s);
+void sensor_retrigger(void);
 void sensor_init(struct sensor *s);
 
 /* Callback for sensor value reporting. */
-- 
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