Re: i2c problems with nodemcu
Posted: Sun May 08, 2016 12:25 pmI modified the original coding slightly. Now it works on my ESP8266-12 with SCL connected to GPIO2 and SDA connected to GPIO0. Both pins are pulled up to VCC with a 2,2kOhm resistor.
Things I changed:
- added a delay of 100ms between the transmitt and the receive command
- read always 3 bytes (2 data bytes + 1 checksum byte)
Things I changed:
- added a delay of 100ms between the transmitt and the receive command
- read always 3 bytes (2 data bytes + 1 checksum byte)
Code: Select all
-- Driver for the Humidity- and Temperature-Sensor HTU21D
htu21df = {
CMD_TEMP_HOLD = 0xE3,
CMD_TEMP_NO_HOLD = 0xF3,
CMD_HUMIDITY_HOLD = 0xE5,
CMD_HUMIDITY_NO_HOLD = 0xF5,
address = 0x40,
id = 0,
-- Initialise the I2C-Bus
-- Parameters:
-- sda - IO-Index of the SDA pin
-- scl - IO-Index of the SCL pin
init = function (self, sda, scl)
self.id = 0
i2c.setup(self.id, sda, scl, i2c.SLOW)
end,
-- Returns the value of the register with the given address
-- Parameters:
-- reg_addr - Address of the register to read
read_reg = function(self, reg_addr)
i2c.start(self.id)
i2c.address(self.id, self.address, i2c.TRANSMITTER)
i2c.write(self.id, reg_addr)
i2c.stop(self.id)
tmr.delay(100000) -- wait for 100ms
i2c.start(self.id)
i2c.address(self.id, self.address, i2c.RECEIVER)
c = i2c.read(self.id, 3)
i2c.stop(self.id)
return c
end,
-- Returns the measured temperature
readTemp = function(self)
h, l = string.byte(self:read_reg(self.CMD_TEMP_HOLD), 1, 2)
h1=bit.lshift(h, 8)
rawtemp = bit.band(bit.bor(h1,l), 0xfffc)
temp = ((rawtemp/65536) * 175.72) - 46.85
return temp
end,
-- Returns the measured humidity
readHum = function(self)
h,l = string.byte(self:read_reg(self.CMD_HUMIDITY_HOLD), 1, 2)
h1=bit.lshift(h, 8)
rawhum = bit.band(bit.bor(h1, 1), 0xfffc)
hum = ((rawhum / 65536) * 125.0) - 6.0
return hum
end
}
sda = 3 --GPIO0 -- declare your I2C interface PIN's
scl = 4 --GPIO2
htu21df:init(sda, scl) -- initialize I2C
temp = htu21df:readTemp() -- read temperature
print(temp) -- print it
hum = htu21df:readHum() -- read humidity
print(hum) -- print it