From 9a6cccaf4a9bb08f712b105ba54b855b272821d5 Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Sat, 16 Nov 2019 14:38:08 +0800
Subject: [PATCH] wavemeter: decimate wavelength output

---
 src/wavemeter.rs | 21 +++++++++++++++------
 wavemeter.json   |  4 +++-
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/src/wavemeter.rs b/src/wavemeter.rs
index 2d4e069..b5877da 100644
--- a/src/wavemeter.rs
+++ b/src/wavemeter.rs
@@ -40,7 +40,9 @@ struct Config {
     position_mon_time: f64, // The time during which position is monitored to compute min/max
     duty_cycle: f64,        // Fraction of the scan used for counting input laser fringes
 
+    debug: bool,            // Enable debug output of wavelength determination code
     motion_cutoff: f64,     // Cut-off frequency of the motion filter
+    decimation: u32,        // Decimation/averaging factor for the final wavelength output
 }
 
 fn read_config_from_file<P: AsRef<Path>>(path: P) -> Result<Config, Box<dyn Error>> {
@@ -145,6 +147,7 @@ fn do_wavemeter(config: &Config) {
 
     let mut first_fringe = 0;
     let mut fringe_count = 0;
+    let mut decimator = noptica::Decimator::new(config.decimation);
 
     noptica::sample(&config.sample_command, |rising, _falling| {
         refpll.tick(rising & (1 << config.bit_ref) != 0);
@@ -176,13 +179,19 @@ fn do_wavemeter(config: &Config) {
                 }
                 if !in_duty & prev_in_duty {
                     let wavelength = (fringe_position - first_fringe).abs()/fringe_count;
-                    let displacement = ((fringe_position - first_fringe).abs() as f64)/(noptica::Dpll::TURN as f64)*config.ref_wavelength;
-                    println!("{:.4} {} {} {:.1}",
-                        (wavelength as f64)/(noptica::Dpll::TURN as f64)*1.0e9*config.ref_wavelength,
-                        fringe_count,
-                        if fringe_position > first_fringe { "UP  " } else { "DOWN" },
-                        1.0e9*displacement);
+                    let wavelength_nm = (wavelength as f64)/(noptica::Dpll::TURN as f64)*1.0e9*config.ref_wavelength;
+                    if config.debug {
+                        let displacement = ((fringe_position - first_fringe).abs() as f64)/(noptica::Dpll::TURN as f64)*config.ref_wavelength;
+                        println!("DEBUG: {:.4} {} {} {:.1}",
+                            wavelength_nm,
+                            fringe_count,
+                            if fringe_position > first_fringe { "UP  " } else { "DOWN" },
+                            1.0e9*displacement);
+                    }
                     fringe_count = 0;
+                    if let Some(wavelength_nm) = decimator.input(wavelength_nm) {
+                        println!("{:.4} nm", wavelength_nm);
+                    }
                 }
                 fringe_count += 1;
                 prev_in_duty = in_duty;
diff --git a/wavemeter.json b/wavemeter.json
index 0ca983e..09c65da 100644
--- a/wavemeter.json
+++ b/wavemeter.json
@@ -15,5 +15,7 @@
     "position_mon_time": 0.25,
     "duty_cycle": 0.9,
 
-    "motion_cutoff": 100e3
+    "debug": false,
+    "motion_cutoff": 100e3,
+    "decimation": 50
 }