Miceuz
commented
8 years ago Hi,
I'm not exactly sure why you get weird readings. Are aware that light measurement takes some time, if you query the sensor before reading is done, it returns the old value. So basically you should wait for ~3 - 5 seconds before reading light measurement result.
Thanks for the code!
On 11/07/2015 12:08 AM, krikk wrote:
hi!
i got your sensor running with a raspberry pi and after a lot of research and tries i got very good readings.. my raspberry pi code:
|#!/usr/bin/python
https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/tree/master/Adafruit_I2C
from Adafruit_I2C import Adafruit_I2C from time import sleep, strftime from datetime import datetime deviceAddr = 0x20 i2c = Adafruit_I2C( deviceAddr, -1, False ) #to change adress #i2c.write8( 1, 0x22 ) #reset sensor, we need this otherwise i get inconsistent light reading in the dark... i2c.write8( deviceAddr, 0x06 ) sleep(5) i2c.write8(deviceAddr, 3) sleep(3) light = i2c.readU16(4, False) temp = i2c.readS16(5, False)/float(10) moisture = i2c.readU16(0, False) print str(temp) + ":"
- str(moisture) + ":" + str(light) |
... only strange thing i noted there was that i had to reset the sensor always before reading values, because otherwise i got strange readings from the light sensor after a few reads... have no clue why... buts that ok with me.
but now i got a shiny new arduino uno and i tried to run your sensor with it, and once again i get wrong readings from the light sensor, e.g. i get a negative reading when measuring in a dark room
i used the provided example code from github a adapted it:
|void loop(){ //Reset i2c moisture sensor Serial.println("Reset i2c moisture sensor"); writeI2CRegister8bit(0x20, 6); //reset delay(5000); writeI2CRegister8bit(0x20, 3); //request light measurement delay(3000); int light = readI2CRegister16bit(0x20, 4); //read light register int moisture = readI2CRegister16bit(0x20, 0); //read capacitance register float temp = readI2CRegister16bit(0x20, 5)/(float)10; //temperature register char tempstr[15]; dtostrf(temp,4, 1, tempstr); Serial.print("moisture: "); Serial.print(moisture); Serial.print(", Temp: "); Serial.print(tempstr); Serial.print(", Light: "); Serial.println(light); delay(2000); } void writeI2CRegister8bit(int addr, int value) { Wire.beginTransmission(addr); Wire.write(value); Wire.endTransmission(); } unsigned int readI2CRegister16bit(int addr, int reg) { Wire.beginTransmission(addr); Wire.write(reg); Wire.endTransmission(); delay(20); Wire.requestFrom(addr, 2); unsigned int t = Wire.read() << 8; t = t | Wire.read(); return t; } |
and i noted a few strange things in it:
|unsigned int readI2CRegister16bit(int addr, int reg) { ... } |
why unsigned ?? ...what about negative temperature values (just tested with a cool-pack, give completely wrong values) (this works with my raspberry pi, python code) also the example code does not wait 3 seconds with reading light value after writing...?
all in all the provided example code seems wrong to me... i reads values, but i think there is something wrong with the conversion of the values... would be nice if you could have a look into this or give me some hints what i'm doing wrong... thx
— Reply to this email directly or view it on GitHub https://github.com/Miceuz/i2c-moisture-sensor/issues/2.
[ok]
mic.
Apollon77
sekdiy
krikk
...i first thought resetting the sensor before each reading will get better results, but this is not the case... we all know the light reading is a "hack" so i can live with it...
cheeeeee
hi!
i got your sensor running with a raspberry pi and after a lot of research and tries i got very good readings.. my raspberry pi code:
... only strange thing i noted there was that i had to reset the sensor always before reading values, because otherwise i got strange readings from the light sensor after a few reads... have no clue why... buts that ok with me.
but now i got a shiny new arduino uno and i tried to run your sensor with it, and once again i get wrong readings from the light sensor, e.g. i get a negative reading when measuring in a dark room
i used the provided example code from github a adapted it:
and i noted a few strange things in it:
why unsigned ?? ...what about negative temperature values (just tested with a cool-pack, give completely wrong values) (this works with my raspberry pi, python code) also the example code does not wait 3 seconds with reading light value after writing...?
all in all the provided example code seems wrong to me... i reads values, but i think there is something wrong with the conversion of the values... would be nice if you could have a look into this or give me some hints what i'm doing wrong... thx