From 69ff13a991db8b7b525e447fbdb03d76d48744c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mario=20H=C3=BCttel?= <mario.huettel@gmx.net>
Date: Sat, 9 Jan 2021 22:26:31 +0100
Subject: [PATCH] Add fast moving average filter for faster startup

---
 stm-firmware/adc-meas.c                           | 13 +++++++++++--
 stm-firmware/include/reflow-controller/adc-meas.h |  8 ++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/stm-firmware/adc-meas.c b/stm-firmware/adc-meas.c
index 1526457..e4d0fa2 100644
--- a/stm-firmware/adc-meas.c
+++ b/stm-firmware/adc-meas.c
@@ -303,14 +303,23 @@ void adc_pt1000_disable(void)
 
 static inline __attribute__((optimize("O3"))) void adc_pt1000_filter(float adc_prefiltered_value)
 {
+	float alpha;
+	float res;
+
 	if (filter_startup_cnt > 0) {
 		filter_startup_cnt--;
 		if (filter_startup_cnt == 0)
 			safety_controller_ack_flag_with_key(ERR_FLAG_MEAS_ADC_UNSTABLE, MEAS_ADC_SAFETY_FLAG_KEY);
 	}
 
-	pt1000_res_raw_lf = (1.0f - filter_alpha) * pt1000_res_raw_lf +
-			filter_alpha * ADC_TO_RES(adc_prefiltered_value);
+	res = ADC_TO_RES(adc_prefiltered_value);
+	if (ABS(res - pt1000_res_raw_lf) > 20)
+		alpha = ADC_PT1000_FILTER_WEIGHT_FAST;
+	else
+		alpha = filter_alpha;
+
+	pt1000_res_raw_lf = (1.0f - alpha) * pt1000_res_raw_lf +
+			alpha * res;
 
 	safety_controller_report_timing(ERR_TIMING_MEAS_ADC);
 }
diff --git a/stm-firmware/include/reflow-controller/adc-meas.h b/stm-firmware/include/reflow-controller/adc-meas.h
index 5c07236..073977a 100644
--- a/stm-firmware/include/reflow-controller/adc-meas.h
+++ b/stm-firmware/include/reflow-controller/adc-meas.h
@@ -38,6 +38,12 @@
  */
 #define ADC_PT1000_FILTER_WEIGHT 0.005f
 
+/**
+  * @brief Moving average filter weight used for fast regaulation. This is used when the measured resistance
+  * is more than 20 Ohms away from the current averaged value.
+  */
+#define ADC_PT1000_FILTER_WEIGHT_FAST 0.05
+
 /**
  * @brief ADC channel number of PT1000 sensor input
  */
@@ -99,6 +105,8 @@
  */
 #define ADC_TO_RES(adc) ((float)(adc) / 4096.0f * 2500.0f)
 
+#define RES_TO_ADC(res) ((float)(res) / 2500.0f * 4096.0f)
+
 /**
  * @brief This function sets up the ADC measurement fo the external PT1000 temperature sensor
  *