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ds18b20: Allow some read errors

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Allows a limited number of DS18B20 read failures
before stopping the printer. This is designed to
tolerate spurious read errors, while still stopping
for serious issues.

The printer will stop when the sensor

fails to report a value five times in a row.

Implementation works as follows:
The MCU reports any read errors using a new "fault"
parameter in its answers.
The Python code tracks the number of errors
and triggers the shutdown. This paves the way for
more sophisticated error handling in the future,
as well as an example for other sensors to follow.

Signed-off-by: Lorenzo Pfeifer <Lorenzo.Pfeifer+github@googlemail.com>
This commit is contained in:
functionpointer 2022-06-05 14:26:51 +02:00 • committed by Kevin O'Connor
parent b0da191bee
commit 2dc20c011d
2 changed files with 38 additions and 24 deletions
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7
klippy/extras/ds18b20.py
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@ -10,6 +10,7 @@ DS18_REPORT_TIME = 3.0
# Temperature can be sampled at any time but conversion time is ~750ms, so
# setting the time too low will not make the reports come faster.
DS18_MIN_REPORT_TIME = 1.0
DS18_MAX_CONSECUTIVE_ERRORS = 4
class DS18B20:
def __init__(self, config):
@ -32,7 +33,7 @@ class DS18B20:
def _build_config(self):
sid = "".join(["%02x" % (x,) for x in self.sensor_id])
self._mcu.add_config_cmd("config_ds18b20 oid=%d serial=%s"
% (self.oid, sid))
% (self.oid, sid, DS18_MAX_CONSECUTIVE_ERRORS))
clock = self._mcu.get_query_slot(self.oid)
self._report_clock = self._mcu.seconds_to_clock(self.report_time)
@ -44,7 +45,9 @@ class DS18B20:
def _handle_ds18b20_response(self, params):
temp = params['value'] / 1000.0
if temp < self.min_temp or temp > self.max_temp:
if params["fault"] != 0:
temp = 0 # read error! report 0C and don't check temp range
elif temp < self.min_temp or temp > self.max_temp:
self.printer.invoke_shutdown(
"DS18B20 temperature %0.1f outside range of %0.1f:%.01f"
% (temp, self.min_temp, self.max_temp))