IMU/Altimeter: Finesse elevations that are below sea level. It's magic.

rwaldron · Oct 16, 2015 · ee2f739 · ee2f739
1 parent 0f215d0
commit ee2f739
Showing 1 changed file with 7 additions and 1 deletion.
diff --git a/lib/imu.js b/lib/imu.js
@@ -238,6 +238,7 @@ var Drivers = {
         var io = board.io;
         var address = opts.address || this.ADDRESSES[0];
         var elevation = null;
+        var offset = 0;
         var isPressure = false;
 
         // See http://www.henrylahr.com/?p=99 for implementation approach
@@ -253,6 +254,11 @@ var Drivers = {
           elevation = opts.elevation;
         }
 
+        if (elevation !== null && elevation <= 0) {
+          offset = Math.abs(elevation) + 1;
+          elevation = 1;
+        }
+
         var waitForReady = function(next) {
           io.i2cReadOnce(address, this.REGISTER.STATUS, 1, function(data) {
             if (data[0] & this.MASK.STATUS.PRESSURE_DATA_READ) {
@@ -291,7 +297,7 @@ var Drivers = {
                 altVal = (m << 8 | c) + fl;
                 altNow = (altNow * 3 + altVal) / 4;
 
-                computed.altitude = altNow;
+                computed.altitude = altNow - offset;
               }
 
               isPressure = !isPressure;