Basic program to read temperature and pressure data from BMP-180 altimeter, convert the temperature into Centigrade and Fahrenheit, and average pressure for highest precision. Use pressure to obtain altitude in meters and feet. Display all to four 4-digit eight-segment bubble displays.
main.cpp
- Committer:
- onehorse
- Date:
- 2014-07-03
- Revision:
- 0:06dc60296e6e
File content as of revision 0:06dc60296e6e:
#include "mbed.h" #include "BMP180.h" #include "HT16K33.h" #define BMP180_ADDRESS 0x77<<1 uint32_t delt_t, count, tempcount; float temperature, pressure, temppress, altitude; DigitalOut myled(LED1); BMP180 bmp180; // initialize BMP-180 altimeter HT16K33 led; // initialize bubble display Timer t; Serial pc(USBTX, USBRX); // tx, rx int main() { t.start(); led.initHT16K33(); // initialize bubble display led.clearDsplay(display1); // clear bubble display1 led.clearDsplay(display2); // clear bubble display2 led.clearDsplay(display3); // clear bubble display1 led.clearDsplay(display4); // clear bubble display2 // Read the WHO_AM_I register of the BMP-180, this is a good test of communication uint8_t c = bmp180.readByte(BMP180_ADDRESS, BMP180_WHO_AM_I); if(c == 0x55) { pc.printf("BMP-180 is 0x%x\n\r", c); pc.printf("BMP-180 should be 0x55\n\r"); pc.printf("BMP-180 online...\n\r"); bmp180.BMP180Calibration(); pc.printf("BMP-180 calibration complete...\n\r"); } else { pc.printf("BMP-180 is 0x%x\n\r", c); pc.printf("BMP-180 should be 0x55\n\r"); while(1); // idle here forever } ///////////////////////////////////////////////// // main ///////////////////////////////////////////////// while (1) { // Average over the display duty cycle to get the best pressure and altitude resolution // The sample read time is on the order of 30 ms at the highest resolution using OSS = 3 // Averaging over the display duty cycle is equivalent to averaging about 500/30 ~ 16 times // per display output. If this is too much averaging, one can always reduce the display duty cycle temperature = (float)bmp180.BMP180GetTemperature()/10.0f; // Get temperature from BMP-180 in degrees C temppress += (float)bmp180.BMP180GetPressure(); // Get pressure from BMP-180 in Pa tempcount++; // Serial print and/or display at 0.5 s rate independent of data rates delt_t = t.read_ms() - count; if (delt_t > 500) { // update LCD once per half-second independent of read rate myled=!myled; pressure = temppress/tempcount; // use average pressure for reading to get ultra-high resolution temperature = temperature*9.0f/5.0f + 32.0f; // convert to Fahrenheit altitude = 44330.0f*( 1.0f - pow((pressure/101325.0f), (1.0f/5.255f))); // Calculate altitude in meters led.writeFloat(display1, temperature, 1); // display temperature in degrees Fahrenheit to bubble display led.writeFloat(display2, pressure/1000, 2); // display pressure in mPa to bubble display led.writeFloat(display3, altitude, 1); // display altitude in meters to bubble display led.writeFloat(display4, altitude*3.281f, 1); // display altitude in feet to bubble display pc.printf("Temperature is %.1f C\n\r", temperature); pc.printf("Pressure is %.3f mPa\n\r", pressure/1000.0f); pc.printf("Altitude is %.1f m\n\r", altitude); pc.printf("Altitude is %.1f ft\n\r", altitude*3.2810f); pc.printf("\n\r"); count = t.read_ms(); temppress = 0; tempcount = 0; } } }