toannv17 / dht-sensors-non-blocking

Arduino library DHT-Sensors-Non-Blocking

Description

An Arduino library for the DHT sensor family (DHT11, DHT22,...). With Non-Blocking design to optimize CPU performance.

dht-sensors-non-blocking's Issues

Reading does not work when measure is not called often

Here's a simple example to reproduce this issue on an Arduino Nano, with a DHT type 11 sensor attached to pin D5.

#include <DHT_Async.h>

DHT_Async dhtSensor(5, DHT_TYPE_11);

void setup()
{
    Serial.begin(9600);
}

int i = 0;

void loop()
{
    i++;

    float temperature;
    float humidity;
    if (dhtSensor.measure(&temperature, &humidity))
    {
        Serial.println();
        Serial.print("Got Temperature: ");
        Serial.print(temperature);
        Serial.println(" degC");
    }
    else
    {
        Serial.print(i); Serial.print(" ");
    }
    delay(100);
}

If you remove the delay(100);, you get something like this

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 
Got Temperature: 23.70 degC
111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 
Got Temperature: 23.70 degC
197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 
Got Temperature: 23.70 degC

But with the delay(100); there, you only get one line of ever-increasing numbers (i.e. "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 " and so on) at a rate of close to 10 numbers per second, but you never get any measurement values.

Replacing the delay(100) with the following code also does not help.

auto startTime = millis();
while (millis() - startTime < 100) { }

If seems that if measure is not called often enough, reading the sensor doesn't work. In my case, I can't guarantee my that the code gets to calling measure often enough. I see some timing stuff in DHT_Async.cpp that happens across multiple calls to measure, but those are only a minimum delay, not a maximum. The part where the values are actually read (readData) happens within one call to measure, so I'm not sure why this happens.