MAX31855 Thermocouple-to-Digital Converter driver

Driver for the SPI Thermocouple-to-Digital Converter MAX31855. More...

Detailed Description

Driver for the SPI Thermocouple-to-Digital Converter MAX31855.

         The MAX31855 performs cold-junction compensation and digitizes
         the signal from a K-, J-, N-, T-, S-, R-, or E-type
         thermocouple. The data is output in a signed 14-bit,
         SPI-compatible, read-only format. This converter resolves
         temperatures to 0.25°C, allows readings as high as +1800°C and
         as low as -270°C, and exhibits thermocouple accuracy of ±2°C
         for temperatures ranging from -200°C to +700°C for K-type
         thermocouples.

Note

See the datasheet for more information: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX31855.pdf

This driver doesn't require a MOSI line, as the MAX31855 is a read-only.

Files
file	max31855.h
file	max31855_constants.h
	Internal addresses, registers and constants.
file	max31855_params.h
	Default configuration for the MAX31855 driver.

Data Structures
struct	max31855_params_t
	Device initialization parameters. More...
struct	max31855_t
	Device descriptor for the driver. More...
struct	max31855_data_t
	Data structure for the MAX31855. More...

Enumerations
enum	max31855_fault_t { MAX31855_FAULT_VCC_SHORT = 0 , MAX31855_FAULT_GND_SHORT = 1 , MAX31855_FAULT_OPEN_CIRCUIT = 2 , MAX31855_FAULT_NO_FAULT = 3 }
	Fault status of the MAX31855. More...

Functions
int	max31855_init (max31855_t *dev, const max31855_params_t *params)
	Initialize the given device.
void	max31855_raw_to_data (uint32_t raw_data, max31855_data_t *data)
	Parse the raw data from the MAX31855 to the data structure.
int	max31855_read (max31855_t *dev, max31855_data_t *data)
	Read data from the MAX31855.
void	max31855_read_raw (max31855_t *dev, uint32_t *data)
	Read raw data from the MAX31855.

Enumeration Type Documentation

max31855_fault_t

enum max31855_fault_t

Fault status of the MAX31855.

Enumerator
MAX31855_FAULT_VCC_SHORT	VCC short-circuit.
MAX31855_FAULT_GND_SHORT	GND short-circuit.
MAX31855_FAULT_OPEN_CIRCUIT	Open circuit.
MAX31855_FAULT_NO_FAULT	No fault.

Definition at line 66 of file max31855.h.

Function Documentation

max31855_init()

int max31855_init	(	max31855_t *	dev,
		const max31855_params_t *	params
	)

Initialize the given device.

Parameters

[in,out]	dev	Device descriptor of the driver
[in]	params	Initialization parameters

Return values

0	on success
-ENXIO	invalid SPI device
-EINVAL	invalid SPI CS pin/line

max31855_raw_to_data()

void max31855_raw_to_data	(	uint32_t	raw_data,
		max31855_data_t *	data
	)

Parse the raw data from the MAX31855 to the data structure.

Parameters

[in]	raw_data	Raw data from the MAX31855
[out]	data	Pointer to the data structure.

Precondition

data must not be NULL

max31855_read()

int max31855_read	(	max31855_t *	dev,
		max31855_data_t *	data
	)

Read data from the MAX31855.

This is a shortcut to read raw data and parse it to the data structure.

Parameters

[in]	dev	Device descriptor of the driver
[out]	data	Pointer to the data structure.

Precondition

dev and data must not be NULL

Return values

0	on success
-EIO	if there is an error detected by the MAX31855. For a detailed error description, check the fault field of the data structure. On this case, temperature fields are not valid.

max31855_read_raw()

void max31855_read_raw	(	max31855_t *	dev,
		uint32_t *	data
	)

Read raw data from the MAX31855.

Parameters

[in]	dev	Device descriptor of the driver
[out]	data	Pointer where to store the raw data.

Precondition

dev and data must not be NULL