Matrix - Pressure and Temperature Sensor
Contents
1 Introduction
- The BMP180 is a high precision, ultra-low power small digital pressure sensor for consumer applications in mobile phones, PDAs, GPS navigation devices and outdoor equipments. With a low altitude noise of merely 0.25m at fast conversion time, the BMP180 offers superior performance. The I2C interface allows for easy system integration with a microcontroller.
- The BMP180 is based on piezo-resistive technology for EMC robustness, high accuracy and linearity as well as long term stability.
- The BMP180 consists of a piezo-resistive sensor, an analog to digital converter and a control unit with E2PROM and a serial I2C interface. The E2PROM has stored 176 bit of individual calibration data. This is used to compensate offset, temperature dependence and other parameters of the sensor.
2 Features
- I2C,3.3V
- Pressure data(16 to 19 bit)
- Temperature data(16 bit)
- PCB Dimension(mm): 16 x 16
- Pin Description:
Pin | Description |
SDA | I2C SDA |
SCL | I2C SCL |
5V | Supply Voltage 5V |
GND | Ground |
3 Basic Device Operation
- The mode (ultra low power, standard, high, ultra high resolution) can be selected by the variable oversampling_setting (0, 1, 2, 3) in the C code.
- Calculation of true temperature and pressure in steps of 1Pa (= 0.01hPa = 0.01mbar) and temperature in steps of 0.1°C.
- With the measured pressure p and the pressure at sea level p0 e.g. 1013.25hPa, the altitude in meters can be calculated with the international barometric formula:
- With the measured pressure p and the absolute altitude the pressure at sea level can be calculated:
Thus, a difference in altitude of ∆altitude = 10m corresponds to 1.2hPa pressure change at sea level.
4 Applications
4.1 Connect to NanoPi M1
Refer to the following connection diagram to connect the module to the NanoPi M1:
Connection Details:
Matrix-Pressure_and_Temperature_Sensor | NanoPi M1 |
SDA | Pin3 |
SCL | Pin5 |
5V | Pin4 |
GND | Pin6 |
4.2 Connect to NanoPi 2
Refer to the following connection diagram to connect the module to the NanoPi 2:
Connection Details:
Matrix-Pressure_and_Temperature_Sensor | NanoPi 2 |
SDA | Pin3 |
SCL | Pin5 |
5V | Pin4 |
GND | Pin6 |
4.3 Connect to NanoPi M2 / NanoPi 2 Fire
Refer to the following connection diagram to connect the module to the NanoPi M2/ NanoPi 2 Fire:
Connection Details:
NanoPi M2 | |
SDA | Pin3 |
SCL | Pin5 |
5V | Pin4 |
GND | Pin6 |
4.4 Connect to NanoPC-T2
Refer to the following connection diagram to connect the module to the NanoPC-T2:
Matrix-Pressure_and_Temperature_Sensor_NanoPC-T2
Connection Details:
Matrix-Pressure_and_Temperature_Sensor | NanoPC-T2 |
SDA | Pin6 |
SCL | Pin5 |
5V | Pin29 |
GND | Pin30 |
5 Compile & Run Test Program
Boot your ARM board with Debian and copy the matrix code:
$ apt-get update && apt-get install git $ git clone https://github.com/friendlyarm/matrix.git
If your cloning is done successfully a "matrix" directory will be generated.
Compile and install Matrix:
$ cd matrix $ make && make install
Run test program:
$ matrix-pressure_temp
Note: this module is not plug and play therefore before running the module please make sure it is connected to an ARM board.
Here is what you should observe:
The temperature is 26.6 C The pressure is 983.91 hPa The altitude is 247.18
6 Code Sample
This Matrix code sample can work with all the ARM boards mentioned in this module's wiki. The name of this code sample is "matrix-pressure_and_temperature_sensor". Here is its source code:
int main(int argc, char ** argv) { int ret = -1; int bmpTemp=0, bmpPressure=0; int board; float altitude = 0; if ((board = boardInit()) < 0) { printf("Fail to init board\n"); return -1; } system("modprobe "DRIVER_MODULE); if ((ret = bmp180Read(BMP180_TEMP, &bmpTemp)) != -1) { printf("The temperature is %.1f C\n", (float)bmpTemp / 10); } else { printf("Faided to get humidity\n"); } if ((ret = bmp180Read(BMP180_PRESSURE, &bmpPressure)) != -1) { printf("The pressure is %.2f hPa\n", (float)bmpPressure / 100); } else { printf("Faided to get pressure\n"); } altitude = 44330 * ( 1 - pow( ((float)bmpPressure / 100 / 1013.25), (1/5.255) ) ); printf("The altitude is %.2f m\n", altitude); system("rmmod "DRIVER_MODULE); return 0; }
For more details about this APIs called in this code sample refer to Matrix API reference manual
7 Resources
8 Update Log
8.1 Feb-24-2016
- Added the whole English version
8.2 Feb-26-2016
- Translated into English
8.3 June-23-2016
- Re-organized and simplified wiki