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Barometer Configuration

With 3.2, barometer driver was converted to be fully configurable / reconfigurable.

As a side effect, how related definitions in target.h are interpreted has been changed in large. Measures to keep backward compatibility has been taken, but there might be cases in which working setups with barometer fail to work with 3.2.

This page explains CLI variables/command to configure barometers at runtime to bring barometers back in the working state, as well as changes in default configuration determination for target maintainers.

Barometer configuration with CLI

  • Barometer related CLI variables
baro_bustypeNONE, I2C, SPISpecifies a type of bus a selected barometer device is connected.
baro_i2c_device0 ~ Max I2C bus ordinate for MCU type (1 origin, same as x in I2Cx expression in target.h)Specifies a bus ordinate of the I2C bus the device is connected when baro_bustype is I2C. 0 meanns "none".
baro_i2c_address0 ~ 119 (0x77)Specifies an I2C address of the device in 7-bit representation. 0 is a special value to specify "driver default address". Values 1~7 are invalid and behavior is unpredictable.
baro_spi_device0 ~ Max SPI bus ordinate for MCU type (1 origin, same as x in SPIx expression in target.h)Specifies a bus ordinate of the SPI bus the device is connected when baro_bustype is SPI. 0 means "none".
baro_hardwareNONE, AUTO, BMP280, MS5611, BMP085NONE = Barometer support disabled. AUTO = Firmware will determine device to use under pre-defined rule. BMP280, MS5611 and BMP085 = Explicitly specifies device to use.
  • If the device is SPI connected, CS (Chip Select) pin can be specified with the resource CLI command
Resource nameDescription
BARO_CSSpecifies CS (Chip Select) pin to enable the SPI connected barometer device.
  • Note that not all combination of bus type and devices are built-in for a particular target.

  • A combination of baro_hardware = AUTO, baro_bustype = I2C and baro_i2c_address = 0 will cause all built-in I2C devices types to be scanned on the specified baro_i2c_device, in the order of BMP280, MS5611 and BMP085.

Target definition changes

This section is intended for target maintainers and developers.

USE_BARO_xxx and USE_BARO_SPI_xxx are now independent.

Prior to 3.2, to configure a device xxx on SPI required both USE_BARO_xxx and USE_BARO_SPI_xxx defined (and this combination disabled I2C support for the device xxx). With 3.2, this dependency/relationship has been removed. USE_BARO_xxx configures an I2C variant of the xxx and USE_BARO_SPI_xxx configures an SPI variant of xxx. If both specified, both I2C and SPI variants are configured.

Right now, as inherited from 3.1.7, targets that use SPI connected barometer defines both USE_BARO_xxx and USE_BARO_SPI_xxx, so they are configured for both I2C and SPI variants, in which case, a run time selection will be the SPI variant as explained next.

Default device determination (compile time)

When a single barometer device is configured in the target definition, then the device will be the default device.

When multiple barometer devices are configured in the target definition, then the following rule are applied sequentially to determine the default device.

  1. In an order of pre-defined precedence: BMP280, MS5611 then BMP085; the order was decided based on popularity.
  2. When both I2C and SPI variants are configured, then SPI is selected; it is assumed that the SPI variant is more likely to be onboard.
  3. Note that when baro_bustype = I2C and baro_i2c_address = 0 and baro_hardware = AUTO, then I2C devices on specified I2C bus will be scanned in the order of precedence described in 1 (this is a run time behavior).

Overriding default configuration

If above rule does not bring intended default configuration, macro names DEFAULT_BARO_bbb_xxx can be used to override the rule. See beginning of the sensors/barometer.c for specific macro names.