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Read the concentration of CO2 in ppm from a K30 sensor connected to a Linux board over I2C.
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| #!/usr/bin/env python | |
| """ vim: set ai tw=80: | |
| Accessing the K30 10,000ppm CO2 sensor via I2C, rather than UART, upon Linux | |
| (such as for the Raspberry Pi and other similar embedded systems). | |
| Copyright (c) 2019 George White. | |
| Permission is hereby granted, free of charge, to any person obtaining a copy of | |
| this software and associated documentation files (the "Software"), to deal in | |
| the Software without restriction, including without limitation the rights to | |
| use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of | |
| the Software, and to permit persons to whom the Software is furnished to do so, | |
| subject to the following conditions: | |
| The above copyright notice and this permission notice shall be included in all | |
| copies or substantial portions of the Software. | |
| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
| IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS | |
| FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR | |
| COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER | |
| IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN | |
| CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. | |
| """ | |
| I2C_SLAVE = 0x0703 | |
| CMD_READ_REG = 0x22 | |
| REG_CO2_PPM = 0x08 | |
| import io | |
| import fcntl | |
| class K30Sensor: | |
| def __init__(self, bus, addr=0x68): | |
| self.fr = io.open(bus, "rb", buffering=0) | |
| self.fw = io.open(bus, "wb", buffering=0) | |
| fcntl.ioctl(self.fr, I2C_SLAVE, addr) | |
| fcntl.ioctl(self.fw, I2C_SLAVE, addr) | |
| def write(self, *data): | |
| if type(data) is list or type(data) is tuple: | |
| data = bytes(data) | |
| self.fw.write(data) | |
| def read(self, count): | |
| s = self.fr.read(count) | |
| l = [] | |
| if len(s) != 0: | |
| for n in s: | |
| l.append(ord(n)) | |
| return l | |
| def read_co2_ppm(self): | |
| checksum = (CMD_READ_REG + REG_CO2_PPM) & 0xFF | |
| self.write(CMD_READ_REG, 0, REG_CO2_PPM, checksum) | |
| response = self.read(4) | |
| return ((response[1] & 0xFF) << 8) | (response[2] & 0xFF) | |
| def close(self): | |
| self.fw.close() | |
| self.fr.close() | |
| if __name__ == "__main__": | |
| """ | |
| Demonstrate the use of the K30Sensor class by simply reading the | |
| concentration from the sensor, and printing it to the screen. | |
| """ | |
| with K30Sensor("/dev/i2c-0") as k30: | |
| print("Concentration of CO2: {} ppm".format(k30.read_co2_ppm())) |
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