herosdevices.hardware.raspberrypi.max318xx.max31855¶

Uses Superclass MAX318xx for communication methods and implements MAX31855 specific functions.

Module Contents¶

herosdevices.hardware.raspberrypi.max318xx.max31855.temperature_NIST(t_remote: float, t_ambient: float) → float¶

Correct temperature for ambient effects according to the Adafruit library.

https://github.com/adafruit/Adafruit_CircuitPython_MAX31855/blob/main/adafruit_max31855.py This function applies a correction to the remote thermocouple temperature reading based on the ambient temperature, using the polynomial approximations from the Adafruit MAX31855 library.

Parameters:

t_remote (float) – The remote thermocouple junction temperature in Celsius.
t_ambient (float) – The ambient (cold junction) temperature in Celsius.

Returns:

Corrected temperature in Celsius.

Return type:

float

Raises:

RuntimeError – If the total thermoelectric voltage is out of the expected range.

class herosdevices.hardware.raspberrypi.max318xx.max31855.MAX31855(cs_pins: dict, miso_pin: int = 5, clk_pin: int = 7, invert_sign: bool = False)¶

Bases: herosdevices.hardware.raspberrypi.max318xx.max318xx.MAX318xx

Class to interface with MAX31855 thermocouple-to-digital converter.

Parameters:

cs_pin (int) – Chip select GPIO pin. Default is 24.
miso_pin (int) – MISO GPIO pin. Default is 5.
clk_pin (int) – CLK GPIO pin. Default is 7.
invert_sign (bool) – Whether to invert the sign of the temperature reading (default: False).

read_temperature()¶: Returns the temperature in Celsius.

invert_sign = False¶

static convert_bits(data: list) → tuple[int, int]¶

Convert raw bits from sensor to temperature readings.

Parameters:

data (list) – List of integers representing raw bits.

Returns:

(t_tc, t_ref) where:: t_tc (float): Thermocouple temperature. t_ref (float): Cold junction (reference) temperature.

Return type:

tuple

transform_bytes(data: list) → tuple[int, int]¶

Extract temperature data from raw byte list.

Parameters:

data (list) – List of bytes received from sensor.

Returns:

(t_tc, t_ref): t_tc (float): Thermocouple temperature. t_ref (float): Cold junction (reference) temperature.

Return type:

tuple

read_temp(cs_pin: int, num_registers: int, convert: collections.abc.Callable[[float, float], float]) → float¶: Read temperature on port cs_pin.

cs_pins¶

miso_pin = 9¶

mosi_pin = 10¶

clk_pin = 11¶

write_register(reg_num: int, data_byte: int) → None¶

Write a byte to a specified register.

Parameters:

regNum (int) – Register number to write to.
dataByte (int) – Data byte to write.

read_register(cs_pin: int, num_registers: int, reg_num_start: int | None = None) → list[int]¶

Read one or more bytes starting from a specified register.

Parameters:

cs_pin (int) – Chip select GPIO pin number.
numRegisters (int) – Number of bytes to read.
regNumStart (int, optional) – Starting register number for the read operation.

Returns:

List of bytes read from the device.

Return type:

list

send_byte(byte: int) → None¶

Send a byte via SPI by bit-banging.

Parameters:: byte (int) – Byte value to send.

recv_byte() → int¶

Receive a byte via SPI by bit-banging.

Returns:: Byte received.
Return type:: int

create_dict(values: list[float], observable: str, unit: str) → dict¶: Build dictionary of observables to be returned by the sensor.