lm75: Added support for LM75/LM75A I2C connected temperature sensors (#3101)

Signed-off-by: Boleslaw Ciesielski <combolek@users.noreply.github.com>

klippy/extras/heaters.py

@@ -261,7 +261,7 @@ class PrinterHeaters:
         return self.heaters[heater_name]
     def setup_sensor(self, config):
         modules = ["thermistor", "adc_temperature", "spi_temperature",
-                   "bme280", "htu21d"]
+                   "bme280", "htu21d", "lm75"]
         for module_name in modules:
             self.printer.load_object(config, module_name)
         sensor_type = config.get('sensor_type')

klippy/extras/lm75.py

@@ -0,0 +1,107 @@
+# Support for I2C based LM75/LM75A temperature sensors
+#
+# Copyright (C) 2020  Boleslaw Ciesielski <combolek@users.noreply.github.com>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import logging
+from . import bus
+
+LM75_CHIP_ADDR = 0x48
+LM75_I2C_SPEED = 100000
+LM75_REGS = {
+    'TEMP'   : 0x00,
+    'CONF'   : 0x01,
+    'THYST'  : 0x02,
+    'TOS'    : 0x03,
+    'PRODID' : 0x07    # TI LM75A chips only?
+}
+LM75_REPORT_TIME = .8
+# Temperature can be sampled at any time but the read aborts
+# the current conversion. Conversion time is 300ms so make
+# sure not to read too often.
+LM75_MIN_REPORT_TIME = .5
+
+class LM75:
+    def __init__(self, config):
+        self.printer = config.get_printer()
+        self.name = config.get_name().split()[-1]
+        self.reactor = self.printer.get_reactor()
+        self.i2c = bus.MCU_I2C_from_config(
+            config,
+            default_addr=LM75_CHIP_ADDR,
+            default_speed=LM75_I2C_SPEED
+        )
+        self.mcu = self.i2c.get_mcu()
+        self.report_time = config.getint(
+            'lm75_report_time',
+            LM75_REPORT_TIME,
+            minval=LM75_MIN_REPORT_TIME
+        )
+        self.temp = 0.0
+        self.sample_timer = self.reactor.register_timer(self._sample_lm75)
+        self.printer.add_object("lm75 " + self.name, self)
+        self.printer.register_event_handler("klippy:ready", self.handle_ready)
+
+    def handle_ready(self):
+        self._init_lm75()
+        self.reactor.update_timer(self.sample_timer, self.reactor.NOW)
+
+    def setup_minmax(self, min_temp, max_temp):
+        pass
+
+    def setup_callback(self, cb):
+        self._callback = cb
+
+    def get_report_time_delta(self):
+        return self.report_time
+
+    def degrees_from_sample(self, x):
+        # The temp sample is encoded in the top 9 bits of a 16-bit
+        # value. Resolution is 0.5 degrees C.
+        return x[0] + (x[1] >> 7) * 0.5
+
+    def _init_lm75(self):
+        # Check and report the chip ID but ignore errors since many
+        # chips don't have it
+        try:
+            prodid = self.read_register('PRODID', 1)[0]
+            logging.info("lm75: Chip ID %#x" % prodid)
+        except:
+            pass
+
+    def _sample_lm75(self, eventtime):
+        try:
+            sample = self.read_register('TEMP', 2)
+            self.temp = self.degrees_from_sample(sample)
+        except Exception:
+            logging.exception("lm75: Error reading data")
+            self.temp = 0.0
+            return self.reactor.NEVER
+
+        measured_time = self.reactor.monotonic()
+        self._callback(self.mcu.estimated_print_time(measured_time), self.temp)
+        return measured_time + self.report_time
+
+    def read_register(self, reg_name, read_len):
+        # read a single register
+        regs = [LM75_REGS[reg_name]]
+        params = self.i2c.i2c_read(regs, read_len)
+        return bytearray(params['response'])
+
+    def write_register(self, reg_name, data):
+        if type(data) is not list:
+            data = [data]
+        reg = LM75_REGS[reg_name]
+        data.insert(0, reg)
+        self.i2c.i2c_write(data)
+
+    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("LM75", LM75)