Reading Raw Data from MPL3115A2

[saranyimsrichar]

Hi, I using MPL3115A2 to read barometric pressure and also temperature in my product box (higher than ambient temperature) it cause barometric value is wrong due to internal integrate temperature compensation.

So Datasheet say Raw out put of barometric pressure is no compensated. and it is 20 bits data this is only word show in datasheet.

Do someone have more information of this chip with raw data?
Can raw data will be use?

Thank you in advane

[saranyimsrichar]

Dear Jose,

Thank you for your answer. MPL115A2 is not recommend to new design meaning it will stop production soon?

My application is after market engine control unit I need barometric pressure value to compensate fuel injection. I have to place it on my PCB and it always higher temperature than actual.

Do you have any suggestion?

Thank you

[reyes]

Hi Saran,

There is a SPI version of the MPL115A named MPL115A1. This version of the sensor is in active status.

MPL115A1: http://cache.nxp.com/files/sensors/doc/data_sheet/MPL115A1.pdf

Have a great day,
Jose Reyes

[reyes · Accepted solution]

Hi Saran,

You can read the raw data from the MPL3115A2 when RAW bit is set (CTRL_REG1), then the pressure RAW value is stored in all 24 bits of OUT_P_MSB, OUT_P_CSB and OUT_P_LSB and the temperature RAW value is stored in all 16 bits of OUT_T_MSB and OUT_T_LSB.

However, we strongly do not recommend using the RAW output mode as it outputs ADC data with no post processing (no scaling, no offset correction etc). It is much more convenient to use the processed data.

Unfortunately, the RAW data of the MPL3115A2 is intended to be used only internally by nxp in order to check if there is an error with the embedded compensation algorithm.

What you would need to know in order to know the relationship between the raw data and the pressure data are some coefficient data and the algorithm for the conversion, unfortunately I do not have access to any of this information and I not even think that it can be shared if I had it.

Also, I don’t think that this information would be really useful because you will get the same result that the one you get when reading the pressure data directly from the MPL3115A2, but without doing all the extra conversion and compensation work.

I apologize for the problems this may cause.

Now, if you want to make all this extra procedure you can use the MPL115A2, using this version of the digital pressure sensor you have access of the coefficient data and based on this and the raw data given by the sensor, you need to implement your algorithm externally in order to get the compensated pressure data. But 1 important note is that the MPL115A2 is not recommended for new designs since the MPL3115A2 is replacing this device, because as mentioned, all the compensation is internally made by nxp.

Have a great day,
Jose Reyes

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