refactor ds18 #287

src/ds18.cpp

@@ -39,10 +39,7 @@ void DS18::setup(uint8_t gpio, bool parasite) {
 uint8_t DS18::scan() {
     _devices.clear();
 
-    uint8_t count;
-    
-    // start the search
-    count = loadDevices();
+    uint8_t count = loadDevices(); // start the search
 
     // If no devices found check again pulling up the line
     if (count == 0) {
@@ -59,27 +56,26 @@ uint8_t DS18::scan() {
 // scan every 2 seconds
 void DS18::loop() {
     static uint32_t last = 0;
-    if (millis() - last < DS18_READ_INTERVAL)
+    if (millis() - last < DS18_READ_INTERVAL) {
         return;
+    }
     last = millis();
 
     // Every second we either start a conversion or read the scratchpad
     static bool conversion = true;
     if (conversion) {
-        // Start conversion
         _wire->reset();
         _wire->skip();
         _wire->write(DS18_CMD_START_CONVERSION, _parasite);
     } else {
         // Read scratchpads
         for (unsigned char index = 0; index < _devices.size(); index++) {
-            // Read scratchpad
             if (_wire->reset() == 0) {
-                // Force a CRC check error
-                _devices[index].data[0] = _devices[index].data[0] + 1;
+                _devices[index].data[0] = _devices[index].data[0] + 1; // Force a CRC check error
                 return;
             }
 
+            // Read each scratchpad
             _wire->select(_devices[index].address);
             _wire->write(DS18_CMD_READ_SCRATCHPAD);
 
@@ -89,8 +85,7 @@ void DS18::loop() {
             }
 
             if (_wire->reset() != 1) {
-                // Force a CRC check error
-                _devices[index].data[0] = _devices[index].data[0] + 1;
+                _devices[index].data[0] = _devices[index].data[0] + 1; // Force a CRC check error
                 return;
             }
 
@@ -161,8 +156,9 @@ char * DS18::getDeviceString(char * buffer, unsigned char index) {
     byte 8: SCRATCHPAD_CRC
 */
 int16_t DS18::getRawValue(unsigned char index) {
-    if (index >= _count)
+    if (index >= _count) {
         return 0;
+    }
 
     uint8_t * data = _devices[index].data;
 
@@ -178,23 +174,35 @@ int16_t DS18::getRawValue(unsigned char index) {
         }
     } else {
         byte cfg = (data[4] & 0x60);
-        if (cfg == 0x00)
+        if (cfg == 0x00) {
             raw = raw & ~7; //  9 bit res, 93.75 ms
-        else if (cfg == 0x20)
+        } else if (cfg == 0x20) {
             raw = raw & ~3; // 10 bit res, 187.5 ms
-        else if (cfg == 0x40)
+        } else if (cfg == 0x40) {
             raw = raw & ~1; // 11 bit res, 375 ms
                             // 12 bit res, 750 ms
+        }
     }
 
     return raw;
 }
 
-// return real value as a float
-// The raw temperature data is in units of sixteenths of a degree, so the value must be divided by 16 in order to convert it to degrees.
+// return real value as a float, rounded to 2 decimal places
 float DS18::getValue(unsigned char index) {
-    float value = (float)getRawValue(index) / 16.0;
-    return value;
+    int16_t raw_value = getRawValue(index);
+
+    // check if valid
+    if ((raw_value == DS18_CRC_ERROR) || (raw_value == DS18_DISCONNECTED)) {
+        return (float)DS18_DISCONNECTED;
+    }
+
+    // The raw temperature data is in units of sixteenths of a degree,
+    // so the value must first be divided by 16 in order to convert it to degrees.
+    float new_value = (float)(raw_value / 16.0);
+
+    // round to 2 decimal places
+    // https://arduinojson.org/v6/faq/how-to-configure-the-serialization-of-floats/
+    return (int)(new_value * 100 + 0.5) / 100.0;
 }
 
 // check for a supported DS chip version
@@ -204,8 +212,9 @@ bool DS18::validateID(unsigned char id) {
 
 // return the type
 unsigned char DS18::chip(unsigned char index) {
-    if (index < _count)
+    if (index < _count) {
         return _devices[index].address[0];
+    }
     return 0;
 }
 
@@ -214,6 +223,7 @@ uint8_t DS18::loadDevices() {
     uint8_t address[8];
     _wire->reset();
     _wire->reset_search();
+
     while (_wire->search(address)) {
         // Check CRC
         if (_wire->crc8(address, 7) == address[7]) {