sns(dht): another dht22 variant w/ 12bit values

xoseperez · Mar 5, 2025 · 40500b4 · 40500b4
1 parent 7476793
commit 40500b4
Show file tree

Hide file tree

Showing 2 changed files with 73 additions and 8 deletions.
diff --git a/code/espurna/sensors/DHTSensor.h b/code/espurna/sensors/DHTSensor.h
@@ -82,6 +82,17 @@ float dht_humidity(DHTChipType type, std::array<uint8_t, 2> pair) {
     return out;
 }
 
+float dht_raw_impl(std::array<uint8_t, 2> pair) {
+    int16_t out;
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+    std::swap(pair[0], pair[1]);
+#endif
+    std::memcpy(&out, pair.data(), sizeof(out));
+
+    return out;
+}
+
 float dht_temperature(DHTChipType type, std::array<uint8_t, 2> pair) {
     // binary representation varies between the original chip and its copies
     // by default, check for generic sign-magnitude
@@ -92,6 +103,11 @@ float dht_temperature(DHTChipType type, std::array<uint8_t, 2> pair) {
     // it is enough to only check the sign bit neighbour; possible values are around [0...800]
     constexpr auto NegativeTwoComplementMask = uint8_t{ 0b11000000 };
 
+    // another case is 12bit value instead of full 16bit
+    // in case of negative numbers we'd have to extend it to full 16bit
+    constexpr auto ShortVoidMask = uint8_t{ 0b11111000 };
+    constexpr auto ShortSignMask = uint8_t{ 0b00001000 };
+
     float out;
 
     switch (type) {
@@ -122,15 +138,14 @@ float dht_temperature(DHTChipType type, std::array<uint8_t, 2> pair) {
     case DHT_CHIP_DHT22:
     case DHT_CHIP_AM2301:
     case DHT_CHIP_SI7021:
-        // special exception for negative numbers in twos-complement
+        // negative numbers in twos-complement
         if ((pair[0] & NegativeTwoComplementMask) == NegativeTwoComplementMask) {
-            int16_t tmp;
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-            std::swap(pair[0], pair[1]);
-#endif
-            std::memcpy(&tmp, pair.data(), sizeof(tmp));
-            out = tmp;
-        // fallback works both for the original chips and positive numbers
+            out = dht_raw_impl(pair);
+        // 12bit numbers have to be extended first
+        } else if ((pair[0] & ShortVoidMask) == ShortSignMask) {
+            pair[0] |= ShortVoidMask;
+            out = dht_raw_impl(pair);
+        // otherwise, use the standard copy
         } else {
             out = ((pair[0] & MagnitudeMask) << 8) | pair[1];
             if (pair[0] & SignMask) {

diff --git a/code/test/unit/src/sensor/sensor.cpp b/code/test/unit/src/sensor/sensor.cpp
@@ -15,13 +15,19 @@
 // TODO is ..._SUPPORT wrapping necessary inside of sensor includes?
 // TODO ..._PORT should not be used in the class itself?
 
+// TODO ignore -Wunused-value that comes up here from interrupts() / noInterrupts() usage
+#undef xt_rsil
+#define xt_rsil(X)
+
 #define SENSOR_SUPPORT 1
 #define CSE7766_SUPPORT 1
 #define A02YYU_SUPPORT 1
+#define DHT_SUPPORT 1
 
 #include <espurna/config/sensors.h>
 #include <espurna/sensors/CSE7766Sensor.h>
 #include <espurna/sensors/A02YYUSensor.h>
+#include <espurna/sensors/DHTSensor.h>
 
 #include <memory>
 #include <vector>
@@ -193,6 +199,49 @@ void test_a02yyu_data() {
     TEST_ASSERT_EQUAL_DOUBLE(1.953, ptr->value(0));
 }
 
+void test_dht_data() {
+    constexpr auto a = 0b00011010;
+    constexpr auto b = 0b10000110;
+
+    TEST_ASSERT_EQUAL_FLOAT(56.8f,
+        dht_humidity(DHT_CHIP_DHT12, {0x38, 0x8}));
+    TEST_ASSERT_EQUAL_FLOAT(26.6f,
+        dht_temperature(DHT_CHIP_DHT12, {0x1a, 0x6}));
+    TEST_ASSERT_EQUAL_FLOAT(-26.6f,
+        dht_temperature(DHT_CHIP_DHT12, {0x1a, 0x86}));
+
+    TEST_ASSERT_EQUAL_FLOAT(44.9f,
+        dht_humidity(DHT_CHIP_DHT22, {0x1, 0xc1}));
+    TEST_ASSERT_EQUAL_FLOAT(0.2f,
+        dht_temperature(DHT_CHIP_DHT22, {0x0, 0x2}));
+    TEST_ASSERT_EQUAL_FLOAT(-0.2f,
+        dht_temperature(DHT_CHIP_DHT22, {0x80, 0x2}));
+
+    TEST_ASSERT_EQUAL_FLOAT(92.3f,
+        dht_humidity(DHT_CHIP_DHT22, {0x3, 0x9b}));
+    TEST_ASSERT_EQUAL_FLOAT(2.9f,
+        dht_temperature(DHT_CHIP_DHT22, {0x0, 0x1d}));
+
+    TEST_ASSERT_EQUAL_FLOAT(56.3f,
+        dht_humidity(DHT_CHIP_DHT22, {0x2, 0x33}));
+    TEST_ASSERT_EQUAL_FLOAT(-0.9f,
+        dht_temperature(DHT_CHIP_DHT22, {0xff, 0xf7}));
+
+    TEST_ASSERT_EQUAL_FLOAT(93.0f,
+        dht_humidity(DHT_CHIP_DHT22, {0x3, 0xa2}));
+    TEST_ASSERT_EQUAL_FLOAT(-4.8f,
+        dht_temperature(DHT_CHIP_DHT22, {0xff, 0xd0}));
+    TEST_ASSERT_EQUAL_FLOAT(-4.7f,
+        dht_temperature(DHT_CHIP_DHT22, {0xff, 0xd1}));
+    TEST_ASSERT_EQUAL_FLOAT(-4.6f,
+        dht_temperature(DHT_CHIP_DHT22, {0xff, 0xd2}));
+
+    TEST_ASSERT_EQUAL_FLOAT(88.9f,
+        dht_humidity(DHT_CHIP_DHT22, {0x3, 0x79}));
+    TEST_ASSERT_EQUAL_FLOAT(-2.2f,
+        dht_temperature(DHT_CHIP_DHT22, {0xf, 0xea}));
+}
+
 } // namespace
 } // namespace test
 } // namespace espurna
@@ -202,5 +251,6 @@ int main(int, char**) {
     using namespace espurna::test;
     RUN_TEST(test_cse7766_data);
     RUN_TEST(test_a02yyu_data);
+    RUN_TEST(test_dht_data);
     return UNITY_END();
 }