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--- oak:tutorials:onewiretemp [2016/03/20 14:58]
exeng created
+++ oak:tutorials:onewiretemp [2016/03/26 17:17]
bjh [Initialization and Setup()]
@@ Line 1: / Line 1: @@
-======  "THIS TUTORIAL HAS NOT YET BEEN REVIEWED, PLEASE DO NOT USE UNTIL IT HAS" ======
-===== This tutorial is currently being edited. Please do not update until this statement has be removed. =====
-======Temperature Sensing and the 1-Wire Bus======
+====== Oak: Temperature Sensing and the 1-Wire Bus Lesson ======
-This tutorial demonstrates how to use the Oak to read temperature data from the DS18B20 1-Wire Digital Thermometer and publish that data to the Particle.io Dashboard log. It will also demonstrate how to use the deep sleep capability of the Oak platform to minimize power requirements (if desired) between temperature readings.
+This lesson will demonstrate how to use the Oak to read and publish temperature data from the DS18B20 1-Wire Digital Thermometer.
+=====Components Used:=====
+^ Part       ^ Quantity          ^Identification^
+| Oak with soldered headers |1| |
+| Breadboard| 1| |
+| One Wire Temperature Sensor TO-92| 1| DS18B20|
+| 4.7K Ohm ¼W Resistor| 1| Yellow-Purple-Red|
+| Jumper Wires| 6| |
+[NOTE: You can find an index of the parts in the starter and ultimate kits here: [[oak:tutorials:kit_parts|Starter and Ultimate Kit Parts List]]]
 ===== Concepts: =====
-  * How to connect a 1-Wire DS18B20 digital thermometer to the Oak platform.
+In this lesson we demonstrate how to connect a 1-Wire device to the Oak platform using the 1-Wire bus compatible DS18B20 Digital Thermometer. We demonstrate the use of a pull-up resistor on the DS18B20 device DQ line (1-Wire Bus Data Input/Output). And finally, we show you how to publish the temperature data received from the device to the Particle.io Dashboard log.
-  * How to read DS18S20 temperature data.
-  * How to publish temperature data to the Particle.io Dashboard log.
-  * How to use deep sleep capabilities of the Oak to minimize power usage between readings.
-===== What's required: =====
-  - Oak by Digistump [http://digistump.com/products/145]
-  - An active Particle.io account [https://www.particle.io/]
-  - Your Oak configured with the latest firmware
-  - Your Oak claimed as a device on your Particle.io account
-  - A D18B20 1-Wire Digital Thermometer [http://digistump.com/products/57]
-  - A 4.7K Ohm resister (3.3K and 2.2K can be substituted)
-  - OneWire library supporting the ESP8622
-===== Connecting the DS18B20 device to the Oak =====
+===== Circuit: =====
+{{:oak:tutorials:ds18b20example.jpg?direct@300|}}
-The 1-Wire DS18B20 digital thermometer can operate at either 3.3 volts or 5 volts. Since the Oak is a 3.3V device, in this tutorial we will use the 3.3V supplied by the Oak's VCC 3.3V pin to power the DS18B20. The DS18B20 Data Input/Output lead (DQ) must be pulled up to 3.3V using a 4.7K resister.  While the DS18B20 does support a parasitic mode, this will not be demonstrated in this tutorial. Parasitic mode does not require the DS18B20 VDD lead to be connected to external power, but it does require a strong pullup on the 1-Wire bus. To learn more about operating the DS18B20 in parasitic mode, see the DS18B20 device data sheet (https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf).
+Note the orientation of the leads on the DS18B20 device. From left to right they are: (1) GND, (2) DQ, (3) Vdd.
-===== Publishing Temperature Data =====
+==== Connecting the DS18B20 device to the Oak ====
-The provided example sketch (see below) uses the Particle.io function Particle.publish() to post temperature readings to the particle.io Dashboard log. In order to do this you must have an active Particle.io account, a functional Oak running the latest firmware, and that Oak claimed as an active device on Particle.io.
+The 1-Wire DS18B20 digital thermometer can operate at either 3.3V or 5V. For this lesson we use the 3.3V supplied by the Oak's VCC 3.3V pin. The DS18B20 Data Input/Output lead (DQ) is pulled up to 3.3V by using a 4.7K ohm resister between VCC and the DQ lead.
-The actual command used is:
+=== Fritzing Diagram ===
-Particle.publish("Temp (F)", tempFstring, 60, PRIVATE); where “Temp(F): is the event name and tempFstring is the actual temperature reading in string format.
-For more information and other examples for how to use the Particle.publish function and other Particle device firmware Cloud functions, see https://docs.particle.io/reference/firmware/core/
+  - Oak powered through USB or VIN/GND
+  - The DS18B20 Vdd lead (3) is powered by Oak's VCC (3.3V)
+  - Black wires - Ground connections
+  - Red wires - Oak VCC 3.3V
+  - White wire – pin 2 to DS18B20 DQ 1-Wire bus lead (2)
+  - 4.7K pull-up resister from Oak VCC 3.3V to DS18B20 DQ 1-Wire bus lead (2)
+  - DS18B20 GND lead (1) to Oak GND
-===== Oak Deep Sleep function =====
+If you would like to learn more about the DS18B20 1-Wire device features and capabilities, please refer to the Maxim Integrated datasheet for the device. [[https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf]]
-The Oak is capable of entering a deep sleep to minimize power requirements. This may be desirable if, for example, your Oak will be battery powered. The provided example sketch demonstrates this mode of operation but will also support operating in a non-sleeping mode.
+===== Code: =====
-To indicate to the sketch that sleep mode is desired, we use pin 5 (pulled HIGH) as essentially as "switch". If pin 5 is HIGH when read in setup(), the sketch operate in sleep mode. This will be considered the default operating mode and as such pin 5 will be defined as INPUT_PULLUP.
+==== Particle.publish() ====
-To facilitate the Oak's deep sleep and wake-up capabilities, you must also connect pin 10 (WAKE) to the reset (RST) pin. This allows the Oak to trigger a RESET after a user specified sleep period has expired. While in sleep mode, the sketch will enter and run setup after each time a RESET occurs. In this mode it never enters loop().
+The Particle.io provides a method to display events and data to a Dashboard log that is associated with an active device. Since the Oak does not support serial output through the USB connector, this is a convenient and useful way to view your Oak device output. To take advantage of this functionality, you simply need to create an account on Particle.io, claim your Oak device there and make sure that it is seen and active on Particle.io. You can find more information for Particle.io here: [[https://www.particle.io/]]
-If you prefer to operate the Oak in non-sleep mode, or if you want to prevent it from sleeping (when in sleep mode) to allow for new sketch uploads, pin 5 simple needs to be connected to ground (GND) thus pulling pin 5 LOW. When pin 5 is LOW at power up the sketch will not sleep and does enter loop() where it remains and repeatedly reads and publishes data from the DS18B20 device. This mode consumes more power than does operating in a sleep mode.
+Once you are setup on Particle.io, publishing data to the log is quite simple. The function Particle.publish()allows one to easily send events and data to the log.
-If pin 5 is HIGH at power up (sleep mode), the example sketch will stay in sleep mode as long as pin 5 remains HIGH. If at anytime pin 5 is pulled LOW, the sketch will enter non-sleep mode following the next RESET. Once in non-sleep mode, it will remain in this mode at long as the Oak is powered up regardless of the state of pin 5 (HIGH or LOW).
+<code>
+Particle.publish("Temp (F)", tempFstring, 60, PRIVATE);
+</code>
+Where “Temp(F)" is the event name and tempFstring is the actual temperature reading in string format.
-==== Sleep Mode configuration: ====
+You should see log entries with temperature like this.
+{{:oak:tutorials:ds18b20particlelog.jpg?direct&200|}}
-  - Oak powered through USB or VIN/GND
+For more information and other examples for how to use the Particle.publish function and other Particle device firmware Cloud functions, see [[https://docs.particle.io/reference/firmware/core/]]
-  - The DS18B20 is powered by Oak's VCC (3.3V)
-  - Black wires - Ground connections
+==== getTemp() ====
-  - Red wires - VCC 3.3V connections
+-Wire bus access and protocol is done by the function getTemp(). This is basically the standard DS18B20 example sketch. The only changes made to getTemp() are the addition of temperature conversion to Fahrenheit and modified return errors to provide additional info for any errors encountered by getTemp().
-  - Yellow wire - pin 10 (WAKE) to RESET (RST)
-  - White wire – pin 2 to DS18B20 DQ (note: 4.7K pull-up resister)
+<code>
+// OneWire DS18B20 temperature reader with conversion to degrees F
+float getTemp(){
+  // Returns the temperature from a single 1-Wire DS18S20 in DEG Fahrenheit
+  byte data[12];
+  byte addr[8];
+  if ( !ds.search(addr)) {
+      //no more sensors on chain, reset search
+      //Serial.println("No more addresses.");
+      ds.reset_search();
+      return -1000;
+  }
+  if ( OneWire::crc8( addr, 7) != addr[7]) {
+      //Serial.println("CRC is not valid!");
+      return -2000;
+  }
+  if ( addr[0] != 0x10 && addr[0] != 0x28) {
+      //Serial.print("Device is not recognized");
+      return -3000;
+  }
+  ds.reset();
+  ds.select(addr);
+  ds.write(0x44,1); // start conversion, with parasite power on at the end
+  byte present = ds.reset();
+  ds.select(addr);
+  ds.write(0xBE); // Read Scratchpad
+  for (int i = 0; i < 9; i++) { // we need 9 bytes
+    data[i] = ds.read();
+  }
+  ds.reset_search();
+  byte MSB = data[1];
+  byte LSB = data[0];
+  float tempRead = ((MSB << 8) | LSB); //using two's compliment
+  float TemperatureSum = tempRead / 16;
+  // Convert to degrees Fahrenheit
+  TemperatureSum = TemperatureSum * 9 / 5 + 32;
+  return TemperatureSum;
+} //END getTemp()
+</code>
+==== Initialization and Setup() ====
+DS18B20_Pin defines the pin to use for the 1-Wire bus (DQ line). In this example it is set to pin 2 but can be changed to any pin that can tolerate being pulled up at power on.
+The OakLEDpin, pin 1 is used to provide a visual output when temperature is being read.
+sleepTimeS specifies the delay in seconds between readings. We don't actually sleep but rather simply delay a specified amount of time in seconds before that next temperature update. It's important to keep this relatively coarse as we don't want to flood Particle.io with constant updates to the log. For slow changing inputs, 30 seconds to 1 minute is about right but you can easily change this to suit your own needs.
+<code>
+/*********************************************************************
+  Digistump Oak example reading the DS18B20 digital thermometer with
+  periodic calls to particle.Publish() to log temperature readings.
+  Requires:
+   * Particle.io account to facilitate temperature output.
+   * Digistump Oak with current firmware and active on particle.io
+   * DS18B20 OneWire temperature probe
+   * 4.7K ohm resistor
+   * OneWire library with ESP8266 support
+  Does:
+   * Periodic temperature reads - frequency controlled by sleepTimeS
+   * Publishes readings to particle.io
+**********************************************************************
+*/
+#include <OneWire.h> // Using OneWire lib from the Oak package
+int DS18S20_Pin = 2; // DS18S20 Signal on pin 2
+int OakLEDpin = 1;   // Oak onboard LED pin 1
+int sleepTimeS = 30; // 30 seconds - adjust as needed
+float tempF = 0;     // Temperature in degrees F
+char tempFstring[6]; // Used to store a temperature value as a string
+//Temperature chip i/o
+OneWire ds(DS18S20_Pin);
+void setup(void) {
+  pinMode(OakLEDpin, OUTPUT);
+  digitalWrite(OakLEDpin,HIGH); // Turn on onboard LED
+  Particle.publish("Oak Setup", "Started", 60, PRIVATE);
+  if (!ds.reset()) {
+     Particle.publish("Oak Setup", "DS18B20 not found", 60, PRIVATE);
+  }
+  else {
+     Particle.publish("Oak Setup", "DS18B20 present", 60, PRIVATE);
+     // Discard first reading (sometimes in error after power up)
+     tempF = getTemp(); // Ignore this one
+     delay(1000);
+     tempF = getTemp(); // Use this reading
+     sprintf(tempFstring, "%d", (int)tempF); // Convert to string
+     Particle.publish("Temp (F)", tempFstring, 60, PRIVATE);
+  }
+  Particle.publish("Oak Setup", "Complete", 60, PRIVATE);
+  delay(1000); // Pluse stretch onboard LED
+  digitalWrite(OakLEDpin,LOW);
+} //END setup()
+</code>
+==== Main loop() ====
+Once we enter loop() the example sketch continues to read temperature from the DS18B20 and publishes the reading and/or errors to the Particle.io Dashboard log. The Oak onboard LED is simply used to provide a visual (local display) of activity. There is a user specified delay between each call to getTemp() to provide course updates to Particle.io.
+<code>
+void loop(void) {
+  // Get DS18B20 device temperature readings a publish to Particle.io Dashboard log.
+  digitalWrite(OakLEDpin,HIGH); // Turn on onboard LED
+  tempF = getTemp();
+  sprintf(tempFstring, "%d", (int)tempF); // Convert to string
+  // Check for errors (-1000 no device, -2000 CRC error, -3000 device not recognized)
+  if(tempF <= -1000) {
+    Particle.publish("DS18B20 Error", tempFstring, 60, PRIVATE);
+  }
+  else {
+    Particle.publish("Temp (F)", tempFstring, 60, PRIVATE);
+  }
+  digitalWrite(OakLEDpin,LOW); // Turn off onboard LED
+  // Delay sleepTimeS number of seconds before next read
+  for(int i=0; i<sleepTimeS; i++) {
+     delay(1000); // This delay * sleepTimes slows updates to particle.io log
+  }
+} //END loop()
+</code>
-[[oak-temp-sensing-1-wire-bus-1.jpg|{{oak-temp-sensing-1-wire-bus-1.jpg}}]]
+===== Conclusion: =====
-=== Sleep Mode Configuration ===
+In this lesson we demonstrated how to connect a 1-Wire device to the Oak and read temperature data from a 1-Wire DS18B20 digital thermometer. We also demonstrated how to publish that data to the Particle.io Dashboard log. We hope that you found this lesson to be both useful and informative. If you would like to explore the 1-Wire bus protocols and other 1-Wire devices, a simple search should yield plenty of useful information, tutorials and examples. As for the DS18B20 Digital Thermometer, why not drop a waterproof version of the device into your pool and have it tell you when the water is fine or simply use it as the basis for a home grown weather station.
-In Sleep Mode (after reading and publishing temperature data) the Oak enters deep sleep and delays for a user specified number of seconds. When sleep time has expired, a RESET is triggered via pin 10 (WAKE). Following a RESET, the sketch starts from the beginning and never enters loop().

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