Library and demo program for MS4525DO differential pressure sensor based pitot tube, using I2C interface
Temperature values are correct. But I dont trust the PSI and airspeed (especially airspeed).
Code blended and ported from a combination of the following sources:
- https://forum.arduino.cc/index.php?topic=309653.0
- https://github.com/PX4/Firmware/blob/master/src/modules/commander/airspeed_calibration.cpp
- https://github.com/PX4/Firmware/tree/master/src/drivers/differential_pressure/ms4525
Diff: MS4525DO/MS4525DO.h
- Revision:
- 0:5965bf423184
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/MS4525DO/MS4525DO.h Fri Sep 13 08:41:37 2019 +0000 @@ -0,0 +1,73 @@ + +#ifndef MS4525DO_H +#define MS4525DO_H + +#include "mbed.h" + +#define I2C_ADDRESS_MS4525DO 0x28 /**< 7-bit address =0x28. 8-bit is 0x50. Depends on the order code (this is for code "I") */ + +/* Register address */ +#define ADDR_READ_MR 0x00 /* write to this address to start conversion */ + +// MS4525D sensor full scale range and units +const int16_t MS4525FullScaleRange = 1; // 1 psi + +// MS4525D Sensor type (A or B) comment out the wrong type assignments +// Type A (10% to 90%) +const int16_t MS4525MinScaleCounts = 1638; +const int16_t MS4525FullScaleCounts = 14746; + +const int16_t MS4525Span=MS4525FullScaleCounts-MS4525MinScaleCounts; + +//MS4525D sensor pressure style, differential or otherwise. Comment out the wrong one. +//Differential +const int16_t MS4525ZeroCounts=(MS4525MinScaleCounts+MS4525FullScaleCounts)/2; + + +class MS4525DO +{ + public: + // instance methods + // explicit I2C pin names + MS4525DO(PinName sda, PinName sck, char slave_adr = I2C_ADDRESS_MS4525DO); + + // pin names as an object (ideal when sharing the bus) + MS4525DO(I2C &i2c_obj, char slave_adr = I2C_ADDRESS_MS4525DO); + + virtual ~MS4525DO(); + + // public functions + void initialize(void); + int measure(void); // returns status of measurement + float getPSI(void); // returns the PSI of last measurement + float getTemperature(void); // returns temperature of last measurement + float getAirSpeed(void); // calculates and returns the airspeed + int calibrate(void); // attempts to calibrate and returns a status code + + + private: + I2C *i2c_p; + I2C &i2c; + char address; + char _status; + float psi; + float temperature; + float airspeed; + uint16_t P_dat; // 14 bit pressure data + uint16_t T_dat; // 11 bit temperature data + + // private functions + int collect(void); + char fetch_pressure(uint16_t &P_dat, uint16_t &T_dat); + + +}; // end of the class + + +/** airspeed scaling factors; out = (in * Vscale) + offset */ +struct airspeed_scale { + float offset_pa; + float scale; +}; + +#endif