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| Rev | Author | Line No. | Line |
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| 1993 | - | 1 | /* |
| 2 | MS561101BA_altitude.pde - Computes altitude from sea level using pressure readings from the sensor. |
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| 3 | The algorithm uses the Hypsometric formula as explained in http://keisan.casio.com/has10/SpecExec.cgi?path=06000000.Science%2F02100100.Earth%20science%2F12000300.Altitude%20from%20atmospheric%20pressure%2Fdefault.xml&charset=utf-8 |
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| 4 | TODO: The results are not that good. Suggestions on improvements welcome. |
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| 5 | |||
| 6 | Copyright (C) 2011 Fabio Varesano <fvaresano@yahoo.it> |
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| 7 | |||
| 8 | Development of this code has been supported by the Department of Computer Science, |
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| 9 | Universita' degli Studi di Torino, Italy within the Piemonte Project |
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| 10 | http://www.piemonte.di.unito.it/ |
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| 11 | |||
| 12 | |||
| 13 | This program is free software: you can redistribute it and/or modify |
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| 14 | it under the terms of the version 3 GNU General Public License as |
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| 15 | published by the Free Software Foundation. |
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| 16 | |||
| 17 | This program is distributed in the hope that it will be useful, |
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| 18 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 19 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 20 | GNU General Public License for more details. |
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| 21 | |||
| 22 | You should have received a copy of the GNU General Public License |
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| 23 | along with this program. If not, see <http://www.gnu.org/licenses/>. |
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| 24 | |||
| 25 | */ |
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| 26 | |||
| 27 | |||
| 28 | //#define DEBUG_V |
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| 29 | |||
| 30 | #include <Wire.h> |
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| 31 | //#include <DebugUtils.h> |
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| 32 | #include <MS561101BA.h> |
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| 33 | |||
| 34 | |||
| 35 | #define MOVAVG_SIZE 32 |
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| 36 | |||
| 37 | MS561101BA baro = MS561101BA(); |
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| 38 | |||
| 39 | float movavg_buff[MOVAVG_SIZE]; |
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| 40 | int movavg_i=0; |
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| 41 | |||
| 42 | const float sea_press = 1013.25; |
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| 43 | float press, temp; |
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| 44 | |||
| 45 | void setup() { |
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| 46 | Wire.begin(); |
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| 47 | Serial.begin(115200); |
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| 48 | delay(1000); |
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| 49 | |||
| 50 | // Suppose that the CSB pin is connected to GND. |
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| 51 | // You'll have to check this on your breakout schematics |
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| 52 | baro.init(MS561101BA_ADDR_CSB_LOW); |
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| 53 | delay(100); |
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| 54 | |||
| 55 | // populate movavg_buff before starting loop |
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| 56 | for(int i=0; i<MOVAVG_SIZE; i++) { |
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| 57 | movavg_buff[i] = baro.getPressure(MS561101BA_OSR_4096); |
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| 58 | } |
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| 59 | } |
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| 60 | |||
| 61 | void loop() { |
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| 62 | Serial.print(" temp: "); |
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| 63 | temp = baro.getTemperature(MS561101BA_OSR_4096); |
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| 64 | Serial.print(temp); |
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| 65 | Serial.print(" degC pres: "); |
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| 66 | pushAvg(baro.getPressure(MS561101BA_OSR_4096)); |
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| 67 | press = getAvg(movavg_buff, MOVAVG_SIZE); |
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| 68 | Serial.print(press); |
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| 69 | Serial.print(" mbar altitude: "); |
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| 70 | Serial.print(getAltitude(press, temp)); |
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| 71 | Serial.println(" m"); |
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| 72 | delay(100); |
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| 73 | } |
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| 74 | |||
| 75 | float getAltitude(float press, float temp) { |
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| 76 | return ((pow((sea_press / press), 1/5.257) - 1.0) * (temp + 273.15)) / 0.0065; |
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| 77 | } |
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| 78 | |||
| 79 | void pushAvg(float val) { |
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| 80 | movavg_buff[movavg_i] = val; |
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| 81 | movavg_i = (movavg_i + 1) % MOVAVG_SIZE; |
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| 82 | } |
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| 83 | |||
| 84 | float getAvg(float * buff, int size) { |
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| 85 | float sum = 0.0; |
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| 86 | for(int i=0; i<size; i++) { |
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| 87 | sum += buff[i]; |
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| 88 | } |
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| 89 | return sum / size; |
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| 90 | } |