AN3914, Modern Altimeter and Barometer System using ... - Freescale

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if (weather_cntr ==120){ //Avg pressure at end of the hour, value averaged from 0 to 5 min. Pressure_5th_115min = ((WeatherPressArray[115]+WeatherPressArray[116]+WeatherPressArray[117]+WeatherPressArray[118]+WeatherPressArray[119])/5); Weather_change = (Pressure_5th_115min - Pressure_1st_5min); if(pressure_second_round_flag ==0) //first time initial 3 hour dP_dt = (((65.0/1023.0)*Weather_change)/2); //note this is for t = 2 hour if(pressure_second_round_flag ==1) //more than initial 3 hour. dP_dt = (((65.0/1023.0)*Weather_change)/3); //divide by 3 as this is the difference in time from 0 value } if (weather_cntr ==155){ //Avg pressure at end of the hour, value averaged from 0 to 5 min. Pressure_6th_150min = ((WeatherPressArray[150]+WeatherPressArray[151]+WeatherPressArray[152]+WeatherPressArray[153]+WeatherPressArray[154])/5); Weather_change = (Pressure_6th_150min - Pressure_1st_5min); if(pressure_second_round_flag ==0) //first time initial 3 hour dP_dt = (((65.0/1023.0)*Weather_change)/2.5); //note this is for t = 2.5 hour if(pressure_second_round_flag ==1) //more than initial 3 hour. dP_dt = (((65.0/1023.0)*Weather_change)/3.5); //divide by 3.5 as this is the difference in time from 0 value } if (weather_cntr ==180){ //Avg pressure at end of the hour, value averaged from 0 to 5 min. Pressure_7th_180min = ((WeatherPressArray[175]+WeatherPressArray[176]+WeatherPressArray[177]+WeatherPressArray[178]+WeatherPressArray[179])/5); Weather_change = (Pressure_7th_180min - Pressure_1st_5min); if(pressure_second_round_flag ==0) //first time initial 3 hour dP_dt = (((65.0/1023.0)*Weather_change)/3); //note this is for t = 3 hour if(pressure_second_round_flag ==1) //more than initial 3 hour. dP_dt = (((65.0/1023.0)*Weather_change)/4); //divide by 4 as this is the difference in time from 0 value Pressure_1st_5min = Pressure_6th_150min; //Equating the pressure at 0 to the pressure at 2 hour after 3 hours have past. pressure_second_round_flag =1; // flag to let you know that this is on the past 3 hour mark. Initialized to 0 outside main loop. } if ((dP_dt > (-0.05)) && (dP_dt 0.05) && (dP_dt (-0.25)) && (dP_dt 0.25) weatherstatus = 3; // Quickly rising HP, not stable weather if (dP_dt < (-0.25)) weatherstatus = 4; // Quickly falling LP, Thunderstorm, not stable //if ((weather_cntr
Display Code to Output to LCD Screen: //ADVANCED DP/Dt SECTION if (weatherstatus == 0){ sprintf(LCDArray, "Stable Weather Patt "); LCD_WR (LCDArray,LR3+0); sprintf(LCDArray, " "); LCD_WR (LCDArray,LR1+8); } if (weatherstatus == 1){ sprintf(LCDArray, "Slowly rising Good Weather"); LCD_WR (LCDArray,LR3+0); sprintf(LCDArray, "Clear/Sunny "); LCD_WR (LCDArray,LR1+8); } if (weatherstatus == 2){ sprintf(LCDArray, "Slowly falling L-Pressure "); LCD_WR (LCDArray,LR3+0); sprintf(LCDArray, "Cloudy/Rain "); LCD_WR (LCDArray,LR1+8); } if (weatherstatus == 3){ sprintf(LCDArray, "Quickly rising H-Press"); LCD_WR (LCDArray,LR3+0); sprintf(LCDArray, "Not Stable"); LCD_WR (LCDArray,LR1+8); } if (weatherstatus == 4){ sprintf(LCDArray, "Quickly falling L-Press"); LCD_WR (LCDArray,LR3+0); sprintf(LCDArray, "Thunderstorm"); LCD_WR (LCDArray,LR1+8); } if (weatherstatus == 5){ sprintf(LCDArray, "Unknown (More Time) "); LCD_WR (LCDArray,LR3+0); sprintf(LCDArray, " "); LCD_WR (LCDArray,LR1+8); } <strong>AN3914</strong> Sensors <strong>Freescale</strong> Semiconductor 11
Page 1 and 2: Freescale Semiconductor Application
Page 3 and 4: Table 2. Pressure vs. Altitude Pres
Page 5 and 6: Pressure Change Altitude Change (m)
Page 7 and 8: Simple Weather Station Code ///////
Page 9: Algorithm Code for Advanced Weather
Page 13 and 14: APPENDIX Table 5. Worldwide Altitud
Page 15: How to Reach Us: Home Page: www.fre

AN3914, Modern Altimeter and Barometer System using ... - Freescale

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