arofarn
/
Adafruit_MicroPython_MAX31685
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Fix SPI device baudrate, polarity, phase usage.

This commit is contained in:
Tony DiCola 2017-12-06 18:13:48 -08:00
parent 36888f86a1
commit 48f0a3b5f2
1 changed files with 7 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
adafruit_max31865.py
View File

@ -72,7 +72,8 @@ class MAX31865:
def __init__(self, spi, cs, rtd_nominal=100, ref_resistor=430.0, wires=2): def __init__(self, spi, cs, rtd_nominal=100, ref_resistor=430.0, wires=2):
self.rtd_nominal = rtd_nominal self.rtd_nominal = rtd_nominal
self.ref_resistor = ref_resistor self.ref_resistor = ref_resistor
self._device = spi_device.SPIDevice(spi, cs) self._device = spi_device.SPIDevice(spi, cs, baudrate=500000,
polarity=0, phase=1)
# Set wire config register based on the number of wires specified. # Set wire config register based on the number of wires specified.
if wires not in (2, 3, 4): if wires not in (2, 3, 4):
raise ValueError('Wires must be a value of 2, 3, or 4!') raise ValueError('Wires must be a value of 2, 3, or 4!')
@ -90,7 +91,6 @@ class MAX31865:
def _read_u8(self, address): def _read_u8(self, address):
# Read an 8-bit unsigned value from the specified 8-bit address. # Read an 8-bit unsigned value from the specified 8-bit address.
with self._device as device: with self._device as device:
device.configure(baudrate=500000, phase=1, polarity=0)
self._BUFFER[0] = address & 0x7F self._BUFFER[0] = address & 0x7F
device.write(self._BUFFER, end=1) device.write(self._BUFFER, end=1)
device.readinto(self._BUFFER, end=1) device.readinto(self._BUFFER, end=1)
@ -99,7 +99,6 @@ class MAX31865:
def _read_u16(self, address): def _read_u16(self, address):
# Read a 16-bit BE unsigned value from the specified 8-bit address. # Read a 16-bit BE unsigned value from the specified 8-bit address.
with self._device as device: with self._device as device:
device.configure(baudrate=500000, phase=1, polarity=0)
self._BUFFER[0] = address & 0x7F self._BUFFER[0] = address & 0x7F
device.write(self._BUFFER, end=1) device.write(self._BUFFER, end=1)
device.readinto(self._BUFFER, end=2) device.readinto(self._BUFFER, end=2)
@ -108,8 +107,7 @@ class MAX31865:
def _write_u8(self, address, val): def _write_u8(self, address, val):
# Write an 8-bit unsigned value to the specified 8-bit address. # Write an 8-bit unsigned value to the specified 8-bit address.
with self._device as device: with self._device as device:
device.configure(baudrate=500000, phase=1, polarity=0) self._BUFFER[0] = (address | 0x80) & 0xFF
self._BUFFER[0] = (address & 0xFF) | 0x80
self._BUFFER[1] = val & 0xFF self._BUFFER[1] = val & 0xFF
device.write(self._BUFFER, end=2) device.write(self._BUFFER, end=2)
@ -195,13 +193,13 @@ class MAX31865:
Celsius. Celsius.
""" """
Rt = self.read_rtd() Rt = self.read_rtd()
Rt //= 32768 Rt /= 32768
Rt *= self.ref_resistor Rt *= self.ref_resistor
Z1 = -_RTD_A Z1 = -_RTD_A
Z2 = _RTD_A * _RTD_A - (4 * _RTD_B); Z2 = _RTD_A * _RTD_A - (4 * _RTD_B)
Z3 = (4 * _RTD_B) / self.rtd_nominal; Z3 = (4 * _RTD_B) / self.rtd_nominal
Z4 = 2 * _RTD_B Z4 = 2 * _RTD_B
temp = Z2 + (Z3 * Rt); temp = Z2 + (Z3 * Rt)
temp = (math.sqrt(temp) + Z1) / Z4 temp = (math.sqrt(temp) + Z1) / Z4
if temp >= 0: if temp >= 0:
return temp return temp