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Inconsistent altitude reading with MPL3115A2

Question asked by Chiranjeevi Kinnera on Aug 5, 2016
Latest reply on Aug 16, 2016 by Mike Stanley

Hi All,

 

We are using MPL3115A2 for altitude measurement. our application demands a real time altitude.

We are running linux on iMX6 and MPL3115 is connected on I2C. Using the evtest application to get the altitude from the input subsystem. Tried both RAW mode and post processing mode.

Following is the output of the evtest, Altitude is calculated as 26*0.0625 = 1.625 Metres ( we actually are testing from 9th floor of the building which is around 53 m high) Interestingly even the freedom sensor kit also shows around 1.5 to 2.0 metres. Can someone please throw some light. we are confused.

 

vent: time 1470274587.595498, -------------- Report Sync ------------

Event: time 1470274588.595494, type 3 (Absolute), code 24 (Pressure), value 26

Event: time 1470274588.595499, -------------- Report Sync ------------

Event: time 1470274589.595494, type 3 (Absolute), code 24 (Pressure), value 20

Event: time 1470274589.595500, -------------- Report Sync ------------

Event: time 1470274590.585493, type 3 (Absolute), code 24 (Pressure), value 27

Event: time 1470274590.585499, -------------- Report Sync ------------

Event: time 1470274591.585494, type 3 (Absolute), code 24 (Pressure), value 29

Event: time 1470274591.585500, -------------- Report Sync ------------

Event: time 1470274592.575494, type 3 (Absolute), code 24 (Pressure), value 23

Event: time 1470274592.575499, -------------- Report Sync ------------

Event: time 1470274593.575493, type 3 (Absolute), code 24 (Pressure), value 30

Event: time 1470274593.575499, -------------- Report Sync ------------

Event: time 1470274594.575497, type 3 (Absolute), code 24 (Pressure), value 34

Event: time 1470274594.575503, -------------- Report Sync ------------

Event: time 1470274595.565499, type 3 (Absolute), code 24 (Pressure), value 24

Event: time 1470274595.565504, -------------- Report Sync ------------

Event: time 1470274596.565497, type 3 (Absolute), code 24 (Pressure), value 25

Event: time 1470274596.565502, -------------- Report Sync ------------

Event: time 1470274598.555505, type 3 (Absolute), code 24 (Pressure), value 18

Event: time 1470274598.555511, -------------- Report Sync ------------

Event: time 1470274599.555505, type 3 (Absolute), code 24 (Pressure), value 25

Event: time 1470274599.555510, -------------- Report Sync ------------

Event: time 1470274600.546570, type 3 (Absolute), code 24 (Pressure), value 20

Event: time 1470274600.546576, -------------- Report Sync ------------

Event: time 1470274601.545484, type 3 (Absolute), code 24 (Pressure), value 31

Event: time 1470274601.545490, -------------- Report Sync ------------

Event: time 1470274602.545487, type 3 (Absolute), code 24 (Pressure), value 20

Event: time 1470274602.545493, -------------- Report Sync ------------

Event: time 1470274604.535496, type 3 (Absolute), code 24 (Pressure), value 19

Event: time 1470274604.535501, -------------- Report Sync ------------

Event: time 1470274605.525512, type 3 (Absolute), code 24 (Pressure), value 18

Event: time 1470274605.525517, -------------- Report Sync ------------

Event: time 1470274606.525512, type 3 (Absolute), code 24 (Pressure), value 15

Event: time 1470274606.525517, -------------- Report Sync ------------

Event: time 1470274607.525510, type 3 (Absolute), code 24 (Pressure), value 18

Event: time 1470274607.525516, -------------- Report Sync ------------

Event: time 1470274609.515464, type 3 (Absolute), code 24 (Pressure), value 23

Event: time 1470274609.515470, -------------- Report Sync ------------

Event: time 1470274610.505466, type 3 (Absolute), code 24 (Pressure), value 14

Event: time 1470274610.505472, -------------- Report Sync ------------

Event: time 1470274611.505465, type 3 (Absolute), code 24 (Pressure), value 22

Event: time 1470274611.505470, -------------- Report Sync ------------

Event: time 1470274612.505464, type 3 (Absolute), code 24 (Pressure), value 18

Event: time 1470274612.505470, -------------- Report Sync ------------

Event: time 1470274613.495465, type 3 (Absolute), code 24 (Pressure), value 16

Event: time 1470274613.495470, -------------- Report Sync ------------

Event: time 1470274614.495464, type 3 (Absolute), code 24 (Pressure), value 15

Event: time 1470274614.495469, -------------- Report Sync ------------

Event: time 1470274615.485513, type 3 (Absolute), code 24 (Pressure), value 17

Event: time 1470274615.485519, -------------- Report Sync ------------

Event: time 1470274616.485479, type 3 (Absolute), code 24 (Pressure), value 20

 

Thanks in advance!

Best regards,

Chiranjeevi

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