Hi everyone.
I’m trying to read my Seed Grove Multichannel gas sensor. (http://wiki.seeed.cc/Grove-Multichannel_Gas_Sensor/)
I now, in the webpage the’re a red X on Beaglebone, but I thought It was due to lack of python library.
So I started coding from the Arduino cpp library (that works): https://github.com/Seeed-Studio/Mutichannel_Gas_Sensor/blob/master/MutichannelGasSensor.cpp
If I plug the groove, I see it with i2cdetect -r 2:
`
root@beaglebone:~# i2cdetect -r 2
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-2 using read byte commands.
I will probe address range 0x03-0x77.
Continue? [Y/n]
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: – 04 – -- – -- – -- – -- – -- –
10: – -- – -- – -- – -- – -- – -- – -- – --
20: – -- – -- – -- – -- – -- – -- – -- – --
30: – -- – -- – -- – -- – -- – -- – -- – --
40: – -- – -- – -- – -- – -- – -- – -- – --
50: – -- – -- UU UU UU UU – -- – -- – -- – --
60: – -- – -- – -- – -- – -- – -- – -- – --
70: – -- – -- – -- – --
`
At the moment I’m using Adafruit_I2C library to write/read.
This is my Class:
`
class MutichannelGasSensor:
address = None
def init(self, mode=1, address=0x04, i2c=None, **kwargs):
i2c = Adafruit_I2C(0x04, busnum=2, debug=True)
self._device = i2c
self.address=0x04
self.adcValueR0_NH3_Buf = 0;
self.adcValueR0_CO_Buf = 0;
self.adcValueR0_NO2_Buf = 0;
#POWER ON
dta_test = [11,1]
self._device.writeList(self.address, dta_test)
self.calcGas()
def calcGas(self):
how to calc ratio/123
#ledON
dta_test = [10, 1]
self._device.writeList(self.address, dta_test)
time.sleep(1)
A0_0 = self.get_addr_dta(6, 8)
time.sleep(1)
A0_1 = self.get_addr_dta(6, 10)
time.sleep(1)
A0_2 = self.get_addr_dta(6, 12)
print "A0_0: " + str(A0_0)
print "A0_1: " + str(A0_1)
print "A0_2: " + str(A0_2)
def get_addr_dta(self, addr_reg, __dta):
self._device.write8(0x04, addr_reg)
self._device.write8(0x04, __dta)
testArray = self._device.readList(self.address, 2)
dta=0
dta = testArray[0]
dta <<= 8
dta += testArray[1]
if addr_reg == 8: #CH_VALUE_NH3
self.adcValueR0_NH3_Buf = dta;
elif addr_reg == 10: #CH_VALUE_CO
self.adcValueR0_CO_Buf = dta;
elif addr_reg == 12: #CH_VALUE_NO2
self.adcValueR0_NO2_Buf = dta;
return dta
`
The problem is when I call calcGas() and get_addr_dta(6, 8) , get_addr_dta(6, 10) and get_addr_dta(6, 12):
I wrote in three different registers, but I read always the same value from it (A0_0, A0_1 and A0_2) while they’re differente on an Arduino.
Why?
The same function in Arduino is:
`
unsigned int MutichannelGasSensor::get_addr_dta(unsigned char addr_reg, unsigned char __dta){
START:
Wire.beginTransmission(i2cAddress);
Wire.write(addr_reg);
Wire.write(__dta);
Wire.endTransmission(); // stop transmitting
Wire.requestFrom(i2cAddress, 2);
unsigned int dta = 0;
unsigned char raw[10];
int cnt = 0;
while(Wire.available())
{
raw[cnt++] = Wire.read();
}
if(cnt == 0)goto START;
dta = raw[0];
dta <<= 8;
dta += raw[1];
return dta;
}
`
The sensor datasheet is useless: https://raw.githubusercontent.com/SeeedDocument/Grove-Multichannel_Gas_Sensor/master/res/MiCS-6814_Datasheet.pdf
Thank you for the support 