bme280: initial implementation of BME280 environmental sensor
Signed-off-by: Eric Callahan <arksine.code@gmail.com>
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Arksine
KevinOConnor
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# Support for i2c based temperature sensors
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#
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# Copyright (C) 2020 Eric Callahan <arksine.code@gmail.com>
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#
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# This file may be distributed under the terms of the GNU GPLv3 license.
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import bus
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import logging
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REPORT_TIME = .8
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BME280_CHIP_ADDR = 0x76
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BME280_REGS = {
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'CHIP_ID': 0xD0, 'RESET': 0xE0, 'CTRL_HUM': 0xF2,
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'STATUS': 0xF3, 'CTRL_MEAS': 0xF4, 'CONFIG': 0xF5,
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'PRESSURE_MSB': 0xF7, 'PRESSURE_LSB': 0xF8, 'PRESSURE_XLSB': 0xF9,
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'TEMP_MSB': 0xFA, 'TEMP_LSB': 0xFB, 'TEMP_XLSB': 0xFC,
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'HUM_MSB': 0xFD, 'HUM_LSB': 0xFE, 'CAL_1': 0x88, 'CAL_2': 0xE1
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}
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# BME default settings
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STATUS_MEASURING = 1 << 3
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STATUS_IM_UPDATE = 1
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MODE = 1
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class BME280:
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def __init__(self, config):
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self.printer = config.get_printer()
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self.name = config.get_name().split()[-1]
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self.reactor = self.printer.get_reactor()
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self.i2c = bus.MCU_I2C_from_config(
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config, default_addr=BME280_CHIP_ADDR, default_speed=100000)
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self.os_temp = config.getint('bme280_oversample_temp', 2)
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self.os_hum = config.getint('bme280_oversample_hum', 2)
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self.os_pres = config.getint('bme280_oversample_pressure', 2)
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self.temp = self.pressure = self.humidity = self.t_fine = 0.
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self.max_sample_time = \
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(1.25 + (2.3 * self.os_temp) + ((2.3 * self.os_pres) +
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.575) + ((2.3 * self.os_hum) + .575)) / 1000
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self.dig = None
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self.sample_timer = self.reactor.register_timer(self._sample_bme280)
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self.printer.add_object("bme280 " + self.name, self)
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self.printer.register_event_handler("klippy:ready", self.handle_ready)
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def handle_ready(self):
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self._init_bme280()
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self.reactor.update_timer(self.sample_timer, self.reactor.NOW)
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def setup_minmax(self, min_temp, max_temp):
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pass
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def setup_callback(self, cb):
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self._callback = cb
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def get_report_time_delta(self):
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return REPORT_TIME
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def _init_bme280(self):
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def get_twos_complement(val, bit_size):
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if val & (1 << (bit_size - 1)):
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val -= (1 << bit_size)
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return val
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def get_unsigned_short(bits):
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return bits[1] << 8 | bits[0]
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def get_signed_short(bits):
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val = get_unsigned_short(bits)
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return get_twos_complement(val, 16)
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# Check the chip ID, should be 0x60
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chip_id = self.read_register('CHIP_ID', 1)[0]
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if chip_id != 0x60:
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logging.info(
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"bme280: Chip ID mismatch, expected 0x60, received %#x"
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% (chip_id))
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# Make sure non-volatile memory has been copied to registers
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status = self.read_register('STATUS', 1)[0]
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while status & STATUS_IM_UPDATE:
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self.reactor.pause(self.reactor.monotonic() + .01)
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status = self.read_register('STATUS', 1)[0]
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c1 = self.read_register('CAL_1', 26)
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c2 = self.read_register('CAL_2', 7)
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# Read out and calculate the trimming parameters
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dig = {}
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unsigned_keys = ['T1', 'P1']
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idx = 0
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for cnt, prefix in [(3, 'T'), (9, 'P')]:
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for i in range(cnt):
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key = prefix + str(i + 1)
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if key in unsigned_keys:
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dig[key] = get_unsigned_short(c1[idx:idx+2])
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else:
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dig[key] = get_signed_short(c1[idx:idx+2])
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idx += 2
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dig['H1'] = c1[25] & 0xFF
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dig['H2'] = get_signed_short(c2[0:2])
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dig['H3'] = c2[2] & 0xFF
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dig['H4'] = get_twos_complement(
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((c2[3] << 4) & 0xFF0) | (c2[4] & 0x0F), 12)
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dig['H5'] = get_twos_complement(
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(c2[4] & 0x0F) | ((c2[5] << 4) & 0xFF0), 12)
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dig['H6'] = get_twos_complement(c2[6], 8)
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self.dig = dig
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def _sample_bme280(self, eventtime):
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# Enter forced mode
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self.write_register('CTRL_HUM', self.os_hum)
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meas = self.os_temp << 5 | self.os_pres << 2 | MODE
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self.write_register('CTRL_MEAS', meas)
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# wait until results are ready
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status = self.read_register('STATUS', 1)[0]
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while status & STATUS_MEASURING:
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self.reactor.pause(self.reactor.monotonic() + self.max_sample_time)
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status = self.read_register('STATUS', 1)[0]
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data = self.read_register('PRESSURE_MSB', 8)
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pressure_raw = (data[0] << 12) | (data[1] << 4) | (data[2] >> 4)
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temp_raw = (data[3] << 12) | (data[4] << 4) | (data[5] >> 4)
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humid_raw = (data[6] << 8) | data[7]
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self.temp = self._compensate_temp(temp_raw)
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self.pressure = self._compensate_pressure(pressure_raw) / 100.
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self.humidity = self._compensate_humidity(humid_raw)
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measured_time = self.reactor.monotonic()
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self._callback(measured_time, self.temp)
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return measured_time + REPORT_TIME
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def _compensate_temp(self, raw_temp):
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dig = self.dig
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var1 = ((raw_temp / 16384. - (dig['T1'] / 1024.)) * dig['T2'])
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var2 = (
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((raw_temp / 131072.) - (dig['T1'] / 8192.)) *
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((raw_temp / 131072.) - (dig['T1'] / 8192.)) * dig['T3'])
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self.t_fine = var1 + var2
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return self.t_fine / 5120.0
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def _compensate_pressure(self, raw_pressure):
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dig = self.dig
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t_fine = self.t_fine
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var1 = t_fine / 2. - 64000.
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var2 = var1 * var1 * dig['P6'] / 32768.
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var2 = var2 + var1 * dig['P5'] * 2.
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var2 = var2 / 4. + (dig['P4'] * 65536.)
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var1 = (dig['P3'] * var1 * var1 / 524288. + dig['P2'] * var1) / 524288.
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var1 = (1. + var1 / 32768.) * dig['P1']
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if var1 == 0:
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return 0.
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else:
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pressure = 1048576.0 - raw_pressure
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pressure = ((pressure - var2 / 4096.) * 6250.) / var1
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var1 = dig['P9'] * pressure * pressure / 2147483648.
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var2 = pressure * dig['P8'] / 32768.
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return pressure + (var1 + var2 + dig['P7']) / 16.
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def _compensate_humidity(self, raw_humidity):
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dig = self.dig
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t_fine = self.t_fine
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humidity = t_fine - 76800.
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h1 = (
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raw_humidity - (dig['H4'] * 64. + dig['H5'] / 16384. * humidity))
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h2 = (dig['H2'] / 65536. * (1. + dig['H6'] / 67108864. * humidity *
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(1. + dig['H3'] / 67108864. * humidity)))
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humidity = h1 * h2
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humidity = humidity * (1. - dig['H1'] * humidity / 524288.)
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return min(100., max(0., humidity))
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def read_register(self, reg_name, read_len):
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# read a single register
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regs = [BME280_REGS[reg_name]]
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params = self.i2c.i2c_read(regs, read_len)
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return bytearray(params['response'])
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def write_register(self, reg_name, data):
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if type(data) is not list:
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data = [data]
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reg = BME280_REGS[reg_name]
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data.insert(0, reg)
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self.i2c.i2c_write(data)
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def get_status(self, eventtime):
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return {
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'temperature': self.temp,
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'humidity': self.humidity,
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'pressure': self.pressure
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}
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def load_config(config):
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# Register sensor
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pheater = config.get_printer().lookup_object("heater")
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pheater.add_sensor_factory("BME280", BME280)
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