MS5611

[joesaliba]

I am giving another try to the MS5611 pressure sensor.

Is it possible to get suitable readings using a PIC18F14K22?

It needs some 64 bit variable to do some calculations.

Has anyone got a good reading out of these devices?

Regards

Joe

[trastikata]

It needs some 64 bit variable to do some calculations.

Has anyone got a good reading out of these devices?

I did pressure sensors test couple years ago and made a new PCB where I placed all sensors on the same board with PIC18F4553:

MP3H6115A;MPL3115A2;BMP180;BMP280;MS5611;BMP85P;LPS25HB;MS5607;MS5637;BME280;SPL06-001

The purpose was to see how they behave compared to each other in different conditions, temperature drift etc- thus I needed a close to simultaneous pressure data.

Anyway MS5611 and neither of those require 64-bit computations, everything was done on a PIC18F4553. The code is quite old and written in a haste with no commenting but can serve you as a starting point.

Here are some screenshots from those tests, SPL06-001 was really crappy Chinese copy of BMP280 so I excluded it from the data table.

Code Select Expand

SETUP_SENSOR_MS5611:
    Low CS_MS5611
        spi_byte = $1E : GoSub SPI_SEND : GoSub CHOOSE_5MS_DELAY
    High CS_MS5611
   
    Low CS_MS5611
        spi_byte = $A2 : GoSub SPI_SEND
        GoSub SPI_READ : c1_MS5611.Byte1 = spi_byte
        GoSub SPI_READ : c1_MS5611.Byte0 = spi_byte
    High CS_MS5611
    Low CS_MS5611
        spi_byte = $A4 : GoSub SPI_SEND
        GoSub SPI_READ : c2_MS5611.Byte1 = spi_byte
        GoSub SPI_READ : c2_MS5611.Byte0 = spi_byte
    High CS_MS5611
    Low CS_MS5611
        spi_byte = $A6 : GoSub SPI_SEND
        GoSub SPI_READ : c3_MS5611.Byte1 = spi_byte
        GoSub SPI_READ : c3_MS5611.Byte0 = spi_byte
    High CS_MS5611
    Low CS_MS5611
        spi_byte = $A8 : GoSub SPI_SEND
        GoSub SPI_READ : c4_MS5611.Byte1 = spi_byte
        GoSub SPI_READ : c4_MS5611.Byte0 = spi_byte
    High CS_MS5611
    Low CS_MS5611
        spi_byte = $AA : GoSub SPI_SEND
        GoSub SPI_READ : c5_MS5611.Byte1 = spi_byte
        GoSub SPI_READ : c5_MS5611.Byte0 = spi_byte
    High CS_MS5611
    Low CS_MS5611
        spi_byte = $AC : GoSub SPI_SEND
        GoSub SPI_READ : c6_MS5611.Byte1 = spi_byte
        GoSub SPI_READ : c6_MS5611.Byte0 = spi_byte
    High CS_MS5611
Return

START_MS5611_PRESSURE:
    Low CS_MS5611
        spi_byte = $48 : GoSub SPI_SEND '4096 OS   
    High CS_MS5611   
Return

START_MS5611_TEMPERATURE:
    Low CS_MS5611
        spi_byte = $52 : GoSub SPI_SEND '512 OS
    High CS_MS5611 
Return

READ_MS5611_PRESSURE:
    Low CS_MS5611
        spi_byte = $00 : GoSub SPI_SEND
        GoSub SPI_READ : MS5611_pressure.Byte2 = spi_byte
        GoSub SPI_READ : MS5611_pressure.Byte1 = spi_byte
        GoSub SPI_READ : MS5611_pressure.Byte0 = spi_byte
    High CS_MS5611       
Return

READ_MS5611_TEMPERATURE:
    Low CS_MS5611
        spi_byte = $00 : GoSub SPI_SEND
        GoSub SPI_READ : MS5611_temperature.Byte2 = spi_byte
        GoSub SPI_READ : MS5611_temperature.Byte1 = spi_byte
        GoSub SPI_READ : MS5611_temperature.Byte0 = spi_byte
    High CS_MS5611
Return

CALCULATE_MS5611_PRESSURE:
    MS5611_X1 = c5_MS5611 * 256
    MS5611_X1 = MS5611_temperature - MS5611_X1 ' dT
    MS5611_X2 = MS5611_X1 / 8388608 
    MS5611_X2 = (MS5611_X2 * c6_MS5611) + 2000 
    MS5611_X2 = MS5611_X2 / 100
    s_temperature = MS5611_X2
   
    MS5611_B6 = c4_MS5611 / 16384
    MS5611_B6 = MS5611_B6 * c5_MS5611 
    MS5611_B5 = MS5611_temperature / 32768
    MS5611_B4 = c4_MS5611 / 128
    MS5611_B3 = c2_MS5611 * 2
    MS5611_X1 = MS5611_B4 * MS5611_B5
    MS5611_X1 = MS5611_X1 - MS5611_B6
    MS5611_X1 = MS5611_X1 + MS5611_B3
    MS5611_B6 = c5_MS5611 / 1024
    MS5611_B5 = c3_MS5611 / 32
    MS5611_B6 = MS5611_B6 * MS5611_B5
    MS5611_B5 = MS5611_temperature / 32768
    MS5611_B4 = c3_MS5611 / 256
    MS5611_B5 = MS5611_B5 * MS5611_B4
    MS5611_B4 = c1_MS5611 - MS5611_B6 + MS5611_B5
    pressure = MS5611_pressure / 2097152
    pressure = (pressure * MS5611_B4) - MS5611_X1
Return



[joesaliba]

Thanks Trastikata,

I will try change your code as I am using I2C and work with your calculations.

Thank you

Joe

[joesaliba]

Hi Trastikata,

If you find some time, can you please add what variable types are X1, X2 B4, B5, B6, s_temperature and pressure?

Thank you

Joe

[trastikata]

If you find some time, can you please add what variable types are X1, X2 B4, B5, B6, s_temperature and pressure?

I realized you might need that, but forgot to add it yesterday, here it is:

Code Select Expand

Dim c1_MS5611 As Word
Dim c2_MS5611 As Word
Dim c3_MS5611 As Word
Dim c4_MS5611 As Word
Dim c5_MS5611 As Word
Dim c6_MS5611 As Word

Dim s_temperature As SByte
Dim MS5611_temperature As Dword
Dim MS5611_pressure As Dword

Dim MS5611_X1 As Float
Dim MS5611_X2 As Float
Dim MS5611_B3 As Float
Dim MS5611_B4 As Float
Dim MS5611_B5 As Float
Dim MS5611_B6 As Float


[joesaliba]

Thank you Trastikata.

Joe