setup

This module acts as a setup script for the microcontroller programme, providing pin definitions and configuration values for bus devices, then initialising them.

Code listing

"""Setup script for the microcontroller programme.

Provides pin definitions, configuration and initialisation of bus devices
"""
import board
import busio
from adafruit_bus_device.spi_device import SPIDevice
import digitalio
#import adafruit_max31865
from adafruit_max31865 import MAX31865 # lib/adafruit_max31865.py
from adafruit_max31856 import ThermocoupleType, MAX31856 # lib/adafruit_max31856
import pwmio

# Define hardware connections

## SPI pin definitions and configuration
SPI_MISO_PIN = board.GP12
SPI_MOSI_PIN = board.GP11
SPI_SCLK_PIN = board.GP10
SPI_CS_PIN_0 = board.GP14 # MAX31865 #1
SPI_CS_PIN_1 = board.GP13 # MAX31865 #2
SPI_CS_PIN_2 = board.GP9  # MAX31856 #1
SPI_CS_PIN_3 = board.GP8  # MAX31856 #2

SPI_BAUDRATE = 5_000_000 # 5 MHz max clock for ICs

## PWM pin definitions and configuration
PWM_PIN1 = board.GP16
PWM_PIN2 = board.GP17
PWM_PIN3 = board.GP18
PWM_PIN4 = board.GP19
PWM_FREQ = 19_900 # 20 kHz PWM frequency


# Setup SPI bus
SPI = busio.SPI(SPI_SCLK_PIN, MISO=SPI_MISO_PIN, MOSI=SPI_MOSI_PIN)
CS_1 = digitalio.DigitalInOut(SPI_CS_PIN_0)
CS_2 = digitalio.DigitalInOut(SPI_CS_PIN_1)
CS_3 = digitalio.DigitalInOut(SPI_CS_PIN_2)
CS_4 = digitalio.DigitalInOut(SPI_CS_PIN_3)

## Setup SPI devices

### Setup MAX31865 RTD temperature sensor breakout boards

RTD_NOMINAL_RES_PT100 = 100.0
RTD_NOMINAL_RES_PT1000 = 1000.0
RTD_REF_RESISTOR_PT100 = 430.0
RTD_REF_RESISTOR_PT1000 = 4300.0



max31865a = MAX31865(
        SPI,
        CS_1,
        rtd_nominal=RTD_NOMINAL_RES_PT100, 
        ref_resistor=RTD_REF_RESISTOR_PT100,
        wires=4,
        baudrate=SPI_BAUDRATE
    )
"""
"""

max31865b = MAX31865(
        SPI,
        CS_2,
        rtd_nominal=RTD_NOMINAL_RES_PT100, 
        ref_resistor=RTD_REF_RESISTOR_PT100,
        wires=4,
        baudrate=SPI_BAUDRATE
    )

## Configure MAX31865 to run with voltage bias always on and continuous conversion mode
max31865a.auto_convert = True
max31865a.bias = True
max31865b.auto_convert = True
max31865b.bias = True

## Double check configuration by inspecting configuration register and manually writing config value 
## (see datasheet): https://datasheets.maximintegrated.com/en/ds/MAX31865.pdf#page=13
print(max31865a._read_u8(0x00))
max31865a._write_u8(0x80, 0xC1)
print(max31865a._read_u8(0x00))

print(max31865b._read_u8(0x00))
max31865b._write_u8(0x00, 0xC1)
print(max31865b._read_u8(0x00))

### Setup MAX31856 thermocouple temperature sensor breakout board:

max31856a = MAX31856(
        SPI,
        CS_3,                   # Chip Select Pin number (lines 33-37)
        ThermocoupleType.T,     # Thermocouple Type (see lib/adafruit_max31856.py)
        filter_frequency=50,    # 50 Hz or 60 Hz
        auto_conversion=True,   # Auto conversion for faster measurements
        cj_disable=True,        # Disable cold junction compensation to get deltaT
        baudrate=SPI_BAUDRATE
    )
max31856b = MAX31856(
        SPI,
        CS_4,
        ThermocoupleType.K,
        filter_frequency=50,
        auto_conversion=True,
        cj_disable=True,
        baudrate=SPI_BAUDRATE
    )

max31856a_CR1 = max31856a._read_register(0x01, 1)[0]
max31856a._write_u8(0x81, (max31856a_CR1 ^ 0x20)) # Enable averaging mode for MAX31856 (pg 20 in datasheet)



# Setup PWM output for controlling TEC modules

enPin1 = pwmio.PWMOut(PWM_PIN1, frequency=PWM_FREQ, duty_cycle=0)
enPin2 = digitalio.DigitalInOut(PWM_PIN2)
enPin2.direction=digitalio.Direction.OUTPUT
enPin2.value = True

enPin3 = pwmio.PWMOut(PWM_PIN3, frequency=PWM_FREQ, duty_cycle=0)
enPin4 = digitalio.DigitalInOut(PWM_PIN4)
enPin4.direction=digitalio.Direction.OUTPUT
enPin4.value = True