From 73fda4e6a74df78c796a709e8488b42147f05ac5 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 17 Nov 2020 09:53:20 +1100
Subject: [PATCH] AP_Airspeed: cope with zero ratio in SDP3X driver

needed for AP_Periph
---
 libraries/AP_Airspeed/AP_Airspeed_SDP3X.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libraries/AP_Airspeed/AP_Airspeed_SDP3X.cpp b/libraries/AP_Airspeed/AP_Airspeed_SDP3X.cpp
index a8e066c515..b68ef886fa 100644
--- a/libraries/AP_Airspeed/AP_Airspeed_SDP3X.cpp
+++ b/libraries/AP_Airspeed/AP_Airspeed_SDP3X.cpp
@@ -259,6 +259,10 @@ float AP_Airspeed_SDP3X::_correct_pressure(float press)
 
     // airspeed ratio
     float ratio = get_airspeed_ratio();
+    if (!is_positive(ratio)) {
+        // cope with AP_Periph where ratio is 0
+        ratio = 2.0;
+    }
 
     // calculate equivalent pressure correction. This formula comes
     // from turning the dv correction above into an equivalent