DS18B20 readings to JSON

DS18B20 readings to JSON (in serial monitor)

Base code from http://www.pjrc.com/teensy/td_libs_OneWire.html This code in../electronics/Arduino/DS18B20Serial_json.ino

key bits:

You need to allocate a buffer for tempstr <syntaxhighlight>

float celsius, fahrenheit;
String jsn; 
char tempBuf[32] = {0};

</syntaxhighlight> You end the json after you've gone through all the sensors and if you are just starting, create a new json string. Otherwise, Increment to next sensor. <syntaxhighlight>

 if ( !ds.search(addr)) {//this is where it loops to the next address

Serial.println("No more addresses."); Serial.println();

 	jsn = jsn + "}";//so end the json
 	Serial.println(jsn);//and print it out
 	ctr=0;
   ds.reset_search();//if there are no more devices go back to start of list
   delay(250);
   return;
 } else {
 	if (ctr==0){jsn="{";}//must be just beginning, start the json str
 	++ctr;//since we found a device, increment sensor
 }

</syntaxhighlight> The first two bytes of data = ds.read() is the sensor raw temp which gets converted here <syntaxhighlight>

 // convert the data to actual temperature
 unsigned int raw = (data[1] << 8) | data[0];
 if (type_s) {
   raw = raw << 3; // 9 bit resolution default
   if (data[7] == 0x10) {
     // count remain gives full 12 bit resolution
     raw = (raw & 0xFFF0) + 12 - data[6];
   }
 } else {
   byte cfg = (data[4] & 0x60);
   if (cfg == 0x00) raw = raw << 3;  // 9 bit resolution, 93.75 ms
   else if (cfg == 0x20) raw = raw << 2; // 10 bit res, 187.5 ms
   else if (cfg == 0x40) raw = raw << 1; // 11 bit res, 375 ms
   // default is 12 bit resolution, 750 ms conversion time
 }
 celsius = (float)raw / 16.0;
 fahrenheit = celsius * 1.8 + 32.0;
 dtostrf(fahrenheit, 5, 1, tempBuf); //turns float to string
 jsn= jsn + "\"sensor"+ ctr + "\": " + tempBuf + ", ";//appends temp to json

</syntaxhighlight>