Bar30 High-Resolution 300m calibration coefficients

[Class (William Class)]

Hi all, I am interfacing the the Bar30 pressure sensor via I2C, using a TI microcontroller. I am trying to Read the calibrations value from the sensor, but am unsure on what commands to use. The data sheets specifies that there are 6 calibration coefficients which must me read, using the commands A0 tO AC. Here’s where I am having trouble understanding, from A0 to AC there are 13 different commands, but only 6 coefficient are used. How do I know which commands to use?

thanks and sorry for the inconvenience

[EliotBR (Eliot)]

Hi @Class, welcome to the forum

@Class

Here’s where I am having trouble understanding, from A0 to AC there are 13 different commands, but only 6 coefficient are used.

I’m not sure where you got those values from, but they’re not quite correct. The PROM is composed of 7 16-bit registers, where W0 is a bitmap for factory configuration and the CRC, and W1-W6 are for the 6 16-bit unsigned integer calibration coefficients.

The datasheet explains

@MS5837-30BA Datasheet - I2C Interface - Commands

The address of the PROM is embedded inside of the PROM read command using the a2, a1 and a0 bits.

command	bit 0	bit 1	bit 2	bit 3	bit 4	bit 5	bit 6	bit 7	hex values
	PROM	CONV	-	Typ	ad2	ad1	ad0	stop
…	…	…	…	…	…	…	…	…	…
PROM read	1	0	1	0	ad2	ad1	ad0	0	0xA0 to 0xAE

Bits 0-3 of PROM read are 0b1010 = 0xA, and bits 4-7 are 0bxxx0 which is 7 values in the range 0x0 to 0xE, in steps of 2 (since the stop bit is always 0).

You may wish to refer to the implementation in our Arduino library:

bluerobotics/BlueRobotics_MS5837_Library/blob/master/src/MS5837.cpp#L42-L50