I would really like to get OTA working here as it's freezing outside and I have to go there to update the software in the greenhouse control system.
So please, can we have a 'how to' step-by-step guide to OTA? Please?
S.
@eiten I haven't yet made any progress on finding a good VOC sensor, but along the way I did find out something interesting regarding CO2: namely, if you sleep with your bedroom door closed at night, then the odds are good that the CO2 levels rise to surprisingly high and unhealthy levels.
The better CO2 sensors are factory calibrated and never again need recalibration for the life of the sensor (usually around 10 years or so), because they are used in HVAC systems to control fresh air intake to guarantee indoor air quality. As a for instance, here is one such CO2 sensor: https://www.digikey.com/en/products/detail/senseair/006-0-0008/15790694 At around $50 for just the sensor element itself, it's not exactly cheap, but then again, I'd say it's worth it, because who wants to be burdened by remembering to calibrate their CO2 sensors?
Ideally, I'd like to find a sensitive VOC sensor that also will never require calibration.
Nearly all, and maybe all, of the off-the-shelf IAQ montoring stuff that you might buy for, say, $300 or less seems to require periodic calibration. For that reason, this might be one of those occasions where build is rather than buy.
I have success!
(oops, that's suppose to be Timer1)
I only sample for 1/60 of a second. What I did was to back up all the timer registered I used and then resorted them after I was done sampling. (As opposed to initializing the registers in setup and then starting the timer when needed.)
Now I have a Nano sampling the data and sending it to a MySensors Gateway on an RPi3B+ which then sends it to an MQTT broker runing on an old laptop. Also running on the laptop is Home Assistant running inside of VirtualBox.
If MySensors does use Timer1, it appears that restoring the registers allows it to be shared.
//------------------------------------------------------ISR
ISR(TIMER1_OVF_vect){ // interrupt service routine for overflow
TCNT1 = TimerPreloadValue; // must be first line! starts the timer counting again
digitalWrite(TRIGGER_START_SAMPLE_PIN,HIGH);
samplesVolts[--sample]=analogRead(VOLTS_IN_PIN); // decrement before capturing
samplesCurrent[sample]=analogRead(CURRENT_IN_PIN);
digitalWrite(TRIGGER_START_SAMPLE_PIN,LOW);
if (!sample){ // count down to zero
digitalWrite(TRIGGER_START_SAMPLE_PERIOD_PIN,LOW); // indicate that sampling is complete
samplingEnd = micros();
TCCR1B &= 248; // turns off timer
}
}
//------------------------------------------------------sampleOneCycle
void sampleOneCycle(){
// back up timer registers
uint8_t TCNT1_b = TCNT1;
uint8_t TCCR1B_b = TCCR1B;
uint8_t TCCR1A_b = TCCR1A;
uint8_t TIMSK1_b = TIMSK1;
// configure timer which starts the sampling
noInterrupts(); // disable all interrupts
TCCR1A = 0;
TCCR1B = 0;
TCNT1 = TimerPreloadValue; // preload timer
//TCCR1B |= (1 << CS10)|(1 << CS12); // 1024 prescaler
TCCR1B &= 248; // turns off timer?
TIMSK1 |= (1 << TOIE1); // enable timer overflow interrupt ISR
// demark sampling
sample = NUMBER_OF_SAMPLES; // count down to zero
digitalWrite(TRIGGER_START_SAMPLE_PERIOD_PIN,HIGH);
samplingStart = micros();
TCNT1 = 65535; // first trigger right away!
TCCR1B |= 1; // turns on timer
interrupts(); // enable all interrupts
// wait for sampling to be complete
while(digitalRead(TRIGGER_START_SAMPLE_PERIOD_PIN)){};
samplingEnd = micros();
// restore timer registers
TCNT1 = TCNT1_b;
TCCR1B = TCCR1B_b;
TCCR1A = TCCR1A_b;
TIMSK1 = TIMSK1_b;
}
There are air quality monitors that can detect VOCs (volatile organic compounds), and some that claim to pick up marijuana smoke specifically. Devices like the Airthings Wave Plus, uHoo Air Sensor, or Plume Labs Flow could help identify changes in air quality. Another option is checking with industrial-grade smoke detection companies that provide sensors for businesses and schools, and some of them may also have solutions suited for home use.
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