ds18b20: new module for 1-wire temperature sensor (#3462)

Initial commit of code to support 1-wire (Dallas) sensors such
as the DS18B20. Requires Linux kernel drivers to create a file
in /sysfs which is read by this module, and temperature
typically returned to a temperature_fan.

Signed-off-by: Alan Lord <alanslists@gmail.com>
Signed-off-by: Josh Headapohl <joshhead@gmail.com>

klippy/extras/ds18b20.py

@@ -0,0 +1,77 @@
+# Support for 1-wire based temperature sensors
+#
+# Copyright (C) 2020 Alan Lord <alanslists@gmail.com>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import logging
+import mcu
+
+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
+
+class DS18B20:
+    def __init__(self, config):
+        self.printer = config.get_printer()
+        self.name = config.get_name().split()[-1]
+        self.sensor_id = config.get("serial_no")
+        self.temp = self.min_temp = self.max_temp = 0.0
+        self._report_clock = 0
+        self.report_time = config.getfloat(
+            'ds18_report_time',
+            DS18_REPORT_TIME,
+            minval=DS18_MIN_REPORT_TIME
+        )
+        self._mcu = mcu.get_printer_mcu(self.printer, config.get('sensor_mcu'))
+        self.oid = self._mcu.create_oid()
+        self._mcu.register_response(self._handle_ds18b20_response,
+            "ds18b20_result", self.oid)
+        self._mcu.register_config_callback(self._build_config)
+
+    def _build_config(self):
+        self._mcu.add_config_cmd("config_ds18b20 oid=%d serial=%s" % (self.oid,
+            self.sensor_id.encode("hex")))
+
+        clock = self._mcu.get_query_slot(self.oid)
+        self._report_clock = self._mcu.seconds_to_clock(self.report_time)
+        self._mcu.add_config_cmd("query_ds18b20 oid=%d clock=%u rest_ticks=%u"
+            " min_value=%d max_value=%d" % (
+                self.oid, clock, self._report_clock,
+                self.min_temp * 1000, self.max_temp * 1000), is_init=True)
+
+    def _handle_ds18b20_response(self, params):
+        temp = params['value'] / 1000.0
+
+        if 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))
+
+        next_clock      = self._mcu.clock32_to_clock64(params['next_clock'])
+        last_read_clock = next_clock - self._report_clock
+        last_read_time  = self._mcu.clock_to_print_time(last_read_clock)
+        self._callback(last_read_time, temp)
+
+    def setup_minmax(self, min_temp, max_temp):
+        self.min_temp = min_temp
+        self.max_temp = max_temp
+
+    def fault(self, msg):
+        self.printer.invoke_async_shutdown(msg)
+
+    def get_report_time_delta(self):
+        return self.report_time
+
+    def setup_callback(self, cb):
+        self._callback = cb
+
+    def get_status(self, eventtime):
+        return {
+            'temperature': self.temp,
+        }
+
+def load_config(config):
+    # Register sensor
+    pheaters = config.get_printer().load_object(config, "heaters")
+    pheaters.add_sensor_factory("DS18B20", DS18B20)

klippy/extras/heaters.py

@@ -265,7 +265,8 @@ class PrinterHeaters:
     def setup_sensor(self, config):
         modules = ["thermistor", "adc_temperature", "spi_temperature",
                    "bme280", "htu21d", "lm75", "rpi_temperature",
-                   "temperature_mcu"]
+                   "temperature_mcu", "ds18b20"]
+
         for module_name in modules:
             self.printer.load_object(config, module_name)
         sensor_type = config.get('sensor_type')