Interfacing Dust Sensor with MSP430FR5969

Rajkumar Mekala

Other Parts Discussed in Thread: MSP430FR5969

Can any one suggest me how to interface dust sensor with msp430fr5969 .I have done with the code but even though there is no dust, control is moving to isr .I have connected dust sensor output pin to 4.3 of msp430fr5969

over 9 years ago

0 Dennis Eichmann over 9 years ago

Guru 74080 points

It would be helpful to tell the type of sensor you are using. Or explain it's output signal. Furthermore the problem can be located in your code, so posting the relevant part of it could help, too.

0 Rajkumar Mekala over 9 years ago in reply to Dennis Eichmann

Prodigy 80 points

Sensor Type -- SHINYEI PPD42
Initially The output pin of sensor has logic 1 when dust is detected it goes low .

0 Dennis Eichmann over 9 years ago in reply to Rajkumar Mekala

Guru 74080 points

And how does your code for sensing this output look like?

0 Dennis Eichmann over 9 years ago in reply to Rajkumar Mekala

Guru 74080 points

Rajkumar Mekala said:
when dust is detected it goes low

It looks like you have to do some counting to get the concentration.

0 Dennis Eichmann over 9 years ago

Guru 74080 points

This is a little bit too much code to look at. Please narrow down your problem a bit.

0 Rajkumar Mekala over 9 years ago in reply to Dennis Eichmann

Prodigy 80 points

Yes I will be running a timer to calculate the low pulse time period .

0 Rajkumar Mekala over 9 years ago in reply to Dennis Eichmann

Prodigy 80 points

Yes
Initialise port 4 and pin 3 as input
Select interrupt edge as high to low pulse detection
if any dust is detected the output pin goes low so it is a falling edge it enters into isr and i will start a timer which is of 1 sec timer and switch the edge to low to high pulse transition if the dust detected is for 30 sec then after detecting it again it goes low

0 Dennis Eichmann over 9 years ago in reply to Rajkumar Mekala

Guru 74080 points

Are you sure this is how the sensor works? I did not not read the datasheet - how does it signal the concentration? Is it pulsed? Is it a duty cycle?

0 Rajkumar Mekala over 9 years ago in reply to Dennis Eichmann

Prodigy 80 points

Signal concentration is calculated based up on the lowpulseoccuracy

0 Rajkumar Mekala over 9 years ago in reply to Dennis Eichmann

Prodigy 80 points

duration = T_End - T_Start;
lowpulseoccupancy += duration;
if((T_End - T_Start) >= sampletime_ms)
{
ratio = (lowpulseoccupancy/(sampletime_ms*10.0));
concentration = (1.1*pow(ratio,3)-3.8*pow(ratio,2)+520*ratio+0.62);
lowpulseoccupancy = 0;
T_End = T_Start = 0;
Tx_Uart0_String("\r\n");
Tx_Uart0_String("Concentration = ");
sprintf(Buf,"%f",concentration);
Tx_Uart0_String(Buf);
Tx_Uart0_String(" pcs/0.01cf\n\n\n");
GPIO_enableInterrupt(GPIO_PORT_P4,GPIO_PIN3);
}

0 Dennis Eichmann over 9 years ago in reply to Rajkumar Mekala

Guru 74080 points

Maybe the timer in capture mode is what you need here (still don't know the exact output of the sensor). In capture mode you can trigger an interrupt on a falling edge, take the timer value and store it, change the edge to a rising detection and then when the interrupt happens, store the new timer value and compare both to calculate the elapsed time. If your sensor works with a duty cycle output, I would try this way.

0 Rajkumar Mekala over 9 years ago in reply to Dennis Eichmann

Prodigy 80 points

Thanks Denni

I will b trying now and letu know by writing timer capture interrupt for alling and raising edge

0 Dennis Eichmann over 9 years ago in reply to Rajkumar Mekala

Guru 74080 points

Please keep in mind that my suggestion was based on the assumption that the sensor has an output signal as mentioned before. I did not check that.

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Interfacing Dust Sensor with MSP430FR5969