Arduino library for I2C MSP300 pressure transducer.
Experimental
The MSP300 is an industrial digital pressure transducer. This library implements the I2C version (J) of the sensor. The code is written based upon the datasheet, it is not actually tested by me yet.
The library does not implement the SPI or analog version.
Note: be aware to buy the right sensor: PSI/BAR, SPI/I2C/analog and I2C address as these are hardcoded. OK, The pressure value can be converted with Pressure library, see below.
PSI = 1.45037737738e-5 * BAR;
BAR = 6.89475729318e+4 * PSI;
As the sensor is industrial quality, many applications can be realized with it.
Issues, remarks, experience and improvements are welcome, please open an issue on https://github.com/RobTillaart/MSP300.
A read bug has been fixed and this makes all previous versions obsolete.
Version 0.2.0 introduced a breaking change. You cannot set the pins in begin() any more. This reduces the dependency of processor dependent Wire implementations. The user has to call Wire.begin() and can optionally set the Wire pins before calling begin().
Again: be aware to buy the right sensor: PSI/BAR, SPI/I2C/analog and I2C address as these are hardcoded. (OK pressure output can be converted)
- PSI := 100, 200, 300, 500, 1K, 3K, 5K, 10K, 15K
- BAR := 7, 10, 20, 35, 70, 200, 350, 700, 1000
| colour | description |
|---|---|
| RED | 2.7 – 5.0V |
| BLACK | GND |
| GREEN | SCL |
| WHITE | SDA |
| YELLOW | NC |
For Arduino analog output version 3 is also interesting. It provide 0.5-4.5 volt output which matches many ADC ranges.
White wire is the output (page 4 datasheet).
The analog version is not supported in the library.
This library is related to:
- https://github.com/RobTillaart/I2C_ASDX Honeywell pressure sensors
- https://github.com/RobTillaart/MS5611 (I2C) air pressure & temperature sensor
- https://github.com/RobTillaart/MS5611_SPI air pressure & temperature sensor
- https://github.com/RobTillaart/Pressure to convert PSI to BAR and back.
The MSP300 has a fixed address, however there a five different supported. So without a multiplexer you can have up to 5 transducers on one I2C bus. The address is in the product number of the sensor you buy. (check datasheet Page 7).
| code | address | decimal |
|---|---|---|
| 0 | 0x28 | 24 |
| 1 | 0x36 | 54 |
| 2 | 0x46 | 70 |
| 3 | 0x48 | 72 |
| 4 | 0x51 | 81 |
Sometimes you need to control more devices than possible with the default address range the device provides. This is possible with an I2C multiplexer e.g. TCA9548 which creates up to eight channels (think of it as I2C subnets) which can use the complete address range of the device.
Drawback of using a multiplexer is that it takes more administration in your code e.g. which device is on which channel. This will slow down the access, which must be taken into account when deciding which devices are on which channel. Also note that switching between channels will slow down other devices too if they are behind the multiplexer.
The sensor is specified to work at 100 - 400 KHz I2C. An example performance sketch can be used to see the duration of the most important readPT() call.
As I have no hardware yet, the performance figures are not available. It is also not known yet if and how well the sensor operates above and below the specified range.
To elaborate table with measurements.
| I2C clock | readPT() | Notes |
|---|---|---|
| 50000 | ||
| 100000 | ||
| 200000 | ||
| 300000 | ||
| 400000 | max advised speed | |
| 500000 | ||
| 600000 |
Operating the sensor outside the specified range may cause incorrect readings and/or shorten lifetime. This is unknown territory.
#include "MSP300.h"The library has a number of functions which are all quite straightforward.
- MSP300(uint8_t address = 0x20, TwoWire *wire = &Wire) constructor, default address and I2C bus.
- bool begin(int maxValue) initialize internals. maxValue is the maximum pressure the sensor can read.
- bool isConnected() See if address set in constructor is on the bus.
- bool setAddress(const uint8_t deviceAddress) set address runtime e.g. when the address is unknown at compile time.
- uint8_t getAddress() returns address set.
- uint32_t readP() read status and pressure. Does not update the temperature. Returns the raw value which is useful for debugging.
- uint32_t readPT() reads status, pressure and temperature. Returns the raw value which is useful for debugging.
- uint8_t getStatus() returns status. Should be 0 after read.
- float getPressure() returns the pressure in PSI or BAR (whatever sensor you have). For converting PSI to BAR or other pressure unit one can use the Pressure library. See above. Multiple calls will return the same (cached) value. Call readP() or readPT() to update.
- float getTemperature() returns the temperature in degrees Celsius. Compensated range 0..55° Celsius. Multiple calls will return the same (cached) temperature. Call readPT() to update.
Pressure calibration
- void setPressureCounts(int Pmin = 1000, int Pmax = 15000) set the count rates. Use with care. Check datasheet for details.
- int getPmin() return current value.
- int getPmax() return current value.
- int lastError() returns the last error set. Note: will reset the error!
| define | value |
|---|---|
| MSP300_OK | 0 |
| MSP300_RESERVED | 1 |
| MSP300_STALE_DATA | 2 |
| MSP300_READ_ERROR | 3 |
| MSP300_REQUEST_ERROR | 100 |
The examples show the basic working of the functions.
- improve documentation
- get hardware
- test performance
- add examples
- test accuracy?
- improve status / errorhandling
- add Temperature calibration.
- unit tests
- add simple class for the analog version
- MSP300A
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