Created
November 8, 2016 04:49
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Si7021 Sensor Module for Micropython-ESP8266
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from time import sleep_ms | |
from machine import Pin, I2C | |
# Default Address | |
SI7021_I2C_DEFAULT_ADDR = 0x40 | |
# Commands | |
CMD_MEASURE_RELATIVE_HUMIDITY_HOLD_MASTER_MODE = 0xE5 | |
CMD_MEASURE_RELATIVE_HUMIDITY = 0xF5 | |
CMD_MEASURE_TEMPERATURE_HOLD_MASTER_MODE = 0xE3 | |
CMD_MEASURE_TEMPERATURE = 0xF3 | |
CMD_READ_TEMPERATURE_VALUE_FROM_PREVIOUS_RH_MEASUREMENT = 0xE0 | |
CMD_RESET = 0xFE | |
CMD_WRITE_RH_T_USER_REGISTER_1 = 0xE6 | |
CMD_READ_RH_T_USER_REGISTER_1 = 0xE7 | |
CMD_WRITE_HEATER_CONTROL_REGISTER = 0x51 | |
CMD_READ_HEATER_CONTROL_REGISTER = 0x11 | |
class Si7021(object): | |
def __init__(self, i2c_addr = SI7021_I2C_DEFAULT_ADDR): | |
self.addr = i2c_addr | |
self.cbuffer = bytearray(2) | |
self.cbuffer[1] = 0x00 | |
self.i2c = I2C(scl=Pin(5), sda=Pin(4), freq=100000) | |
def write_command(self, command_byte): | |
self.cbuffer[0] = command_byte | |
self.i2c.writeto(self.addr, self.cbuffer) | |
def readTemp(self): | |
self.write_command(CMD_MEASURE_TEMPERATURE) | |
sleep_ms(25) | |
temp = self.i2c.readfrom(self.addr,3) | |
temp2 = temp[0] << 8 | |
temp2 = temp2 | temp[1] | |
return (175.72 * temp2 / 65536) - 46.85 | |
def readRH(self): | |
self.write_command(CMD_MEASURE_RELATIVE_HUMIDITY) | |
sleep_ms(25) | |
rh = self.i2c.readfrom(self.addr, 3) | |
rh2 = rh[0] << 8 | |
rh2 = rh2 | rh[1] | |
return (125 * rh2 / 65536) - 6 |
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