From 5369b928c1c58c1a8cbf8c6c1fef772107949cb0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Robert=20J=C3=B6rdens?= <rj@quartiq.de>
Date: Sun, 31 Mar 2019 11:33:18 +0000
Subject: [PATCH] add get_x_offset

---
 src/iir.rs  | 10 +++++++++-
 src/main.rs |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/iir.rs b/src/iir.rs
index dd31b86..6d02e17 100644
--- a/src/iir.rs
+++ b/src/iir.rs
@@ -27,7 +27,7 @@ fn macc(y0: f32, x: &[f32], a: &[f32]) -> f32 {
 }
 
 impl IIR {
-    pub fn set_pi(&mut self, kp: f32, ki: f32, g: f32) -> Result<(), &'static str> {
+    pub fn set_pi(&mut self, kp: f32, ki: f32, g: f32) -> Result<(), &str> {
         let ki = copysign(ki, kp);
         let g = copysign(g, kp);
         let (a1, b0, b1) =
@@ -52,6 +52,14 @@ impl IIR {
         Ok(())
     }
 
+    pub fn get_x_offset(&self) -> Result<f32, &str> {
+        let b: f32 = self.ba[..3].iter().sum();
+        if abs(b) < f32::EPSILON {
+            return Err("b is zero")
+        }
+        Ok(self.y_offset/b)
+    }
+
     pub fn set_x_offset(&mut self, xo: f32) {
         let b: f32 = self.ba[..3].iter().sum();
         self.y_offset = xo*b;
diff --git a/src/main.rs b/src/main.rs
index 1a90298..83d7c4b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -563,6 +563,7 @@ fn main() -> ! {
 
         IIR_CH[1].set_pi(-0.1, -10.*t, 0.).expect("bad coefficients");
         IIR_CH[1].set_x_offset(0.1*SCALE);
+        IIR_CH[1].get_x_offset().expect("bad coefficients");
     }
 
     cortex_m::interrupt::free(|cs| {