40 lines
1.4 KiB
Python
40 lines
1.4 KiB
Python
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# Copyright 2016 Peter Dahlberg
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import time
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OP_SINGLE_HRES1 = 0x20
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OP_SINGLE_HRES2 = 0x21
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OP_SINGLE_LRES = 0x23
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DELAY_HMODE = 180 # 180ms in H-mode
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DELAY_LMODE = 24 # 24ms in L-mode
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def sample(i2c, mode=OP_SINGLE_HRES1, i2c_addr=0x23):
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"""
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Performs a single sampling. returns the result in lux
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"""
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i2c.writeto(i2c_addr, b"\x00") # make sure device is in a clean state
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i2c.writeto(i2c_addr, b"\x01") # power up
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i2c.writeto(i2c_addr, bytes([mode])) # set measurement mode
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time.sleep_ms(DELAY_LMODE if mode == OP_SINGLE_LRES else DELAY_HMODE)
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raw = i2c.readfrom(i2c_addr, 2)
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i2c.writeto(i2c_addr, b"\x00") # power down again
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# we must divide the end result by 1.2 to get the lux
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return ((raw[0] << 24) | (raw[1] << 16)) // 78642
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