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| author | DavidvtWout <github@yoctobyte.nl> | 2023-09-11 00:51:14 +0200 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2023-09-10 18:51:14 -0400 |
| commit | 8ef0f7d7e3d3b2ac7bc1e80ed3295ceca6bba4e7 (patch) | |
| tree | 4d741cf7286f914f7477bd08b42e629b3b249119 | |
| parent | 2acfa282942c13c725af6a2cb3ea314edf53406f (diff) | |
| download | kutter-8ef0f7d7e3d3b2ac7bc1e80ed3295ceca6bba4e7.tar.gz kutter-8ef0f7d7e3d3b2ac7bc1e80ed3295ceca6bba4e7.tar.xz kutter-8ef0f7d7e3d3b2ac7bc1e80ed3295ceca6bba4e7.zip | |
spi_temperature: Limit maximum temperature in MAX31865.calc_adc() to melting point of platinum (#6320)
Limit the maximum temperature in MAX31865.calc_adc() to the melting
point of platinum. Above this temperature the Callendar-Van Dusem
formula does not make sense. The default value for max_temp is
99999999.9 and at this temperature the result of this formula is
negative. This sets max_sample_value to 0 which causes the mcu
to shutdown.
Set max adc value to (1<<15)-1 . This is needed because the max value of the adc register
of the MAX31865 is 0b1111 1111 1111 1110 which represents
32767 and not 32768.
Signed-off-by: David van 't Wout <github@yoctobyte.nl>
| -rw-r--r-- | klippy/extras/spi_temperature.py | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/klippy/extras/spi_temperature.py b/klippy/extras/spi_temperature.py index 9970a28d..77033b1b 100644 --- a/klippy/extras/spi_temperature.py +++ b/klippy/extras/spi_temperature.py @@ -320,9 +320,10 @@ class MAX31865(SensorBase): def calc_adc(self, temp): # Calculate relative resistance via Callendar-Van Dusen formula: # resistance = rtd_nominal_r * (1 + CVD_A * temp + CVD_B * temp**2) + temp = min(temp, 1768.3) # Melting point of platinum R_div_nominal = 1. + CVD_A * temp + CVD_B * temp * temp adc = int(R_div_nominal / self.adc_to_resist_div_nominal + 0.5) - adc = max(0, min(MAX31865_ADC_MAX, adc)) + adc = max(0, min(MAX31865_ADC_MAX - 1, adc)) adc = adc << 1 # Add fault bit return adc def build_spi_init(self, config): |