From d607ad028f4d344fd6a894a0285fbebeded70e97 Mon Sep 17 00:00:00 2001
From: jfd <jfd@realflightsystems.com>
Date: Wed, 7 Dec 2022 19:42:42 -0800
Subject: [PATCH 1/2] support altitude in meters

---
 src/BARO.cpp | 12 ++++++++++++
 src/BARO.h   |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/BARO.cpp b/src/BARO.cpp
index 23d3f30..8bfe1c9 100644
--- a/src/BARO.cpp
+++ b/src/BARO.cpp
@@ -93,6 +93,18 @@ float LPS22HBClass::readTemperature(void)
   return reading/100;
 }
 
+#define PRESSURE_SEALEVEL_HPA  (1013.25f) /**< Average sea level pressure is 1013.25 hPa */
+float LPS22HBClass::readAltitude(void)
+{
+  float atmospheric = BARO.readPressure(MILLIBAR);
+  /*
+   * The altitude in meters can be calculated
+   * with the international barometric formula
+   */
+  return 44330.0 *
+    (1.0 - pow(atmospheric/PRESSURE_SEALEVEL_HPA, (1.0/5.255)));
+}
+
 int LPS22HBClass::i2cRead(uint8_t reg)
 {
   _wire->beginTransmission(LPS22HB_ADDRESS);
diff --git a/src/BARO.h b/src/BARO.h
index 6a66004..9d29ca7 100644
--- a/src/BARO.h
+++ b/src/BARO.h
@@ -38,7 +38,7 @@ class LPS22HBClass {
 
   float readPressure(int units = KILOPASCAL);
   float readTemperature(void);
-
+  float readAltitude(void);
 private:
   int i2cRead(uint8_t reg);
   int i2cWrite(uint8_t reg, uint8_t val);

From b3a7dd3be69600797a486747bea30a2b98495b34 Mon Sep 17 00:00:00 2001
From: jfd <jfd@realflightsystems.com>
Date: Wed, 7 Dec 2022 19:56:07 -0800
Subject: [PATCH 2/2] update example

---
 examples/ReadPressure/ReadPressure.ino | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/examples/ReadPressure/ReadPressure.ino b/examples/ReadPressure/ReadPressure.ino
index 00bb7c1..59294b0 100644
--- a/examples/ReadPressure/ReadPressure.ino
+++ b/examples/ReadPressure/ReadPressure.ino
@@ -42,6 +42,16 @@ void loop() {
   // print an empty line
   Serial.println();
 
+  // read the sensor value
+  float altitude = BARO.readAltitude();
+  // print the sensor value
+  Serial.print("Altitude = ");
+  Serial.print(altitude);
+  Serial.println(" m");
+
+  // print an empty line
+  Serial.println();
+
   // wait 1 second to print again
   delay(1000);
 }