I am working on building a temperature sensor system with DS18B20, Wifi module ESP8266 ESP 01S, and Arduino Uno.
I am following a code found online:
/*
* ESP8266-01 with multiple DS10B20 temperature sensors
* reads sensors asyncronsly for less blocking time
*
* Use GPIO2 for the sensors, a single 4.7K pullup resisor is needed.
*
*/
#include <OneWire.h>
const int nsensors = 1 // const is to define a read-only variable, so never overwrite it. Int is for integer values (we have an integer number of sensors)
byte sensors[][8] = {
{ 0x28, 0xC1, 0x02, 0x64, 0x04, 0x00, 0x00, 0x35 }
}; // here we are defining the variable sensors with 8 bits, and this will be in our case our one sensor
int16_t tempraw[nsensors]; // here we define the raw temperature vector with a size of 16 bits
unsigned long nextprint = 0; // this can only store positive values and 0 -- nextprint will print temperature values
OneWire ds(2); // on pin 2 (a 4.7K pullup is necessary)
void setup() {
Serial.begin(115200);
delay(10);
Serial.println();
Serial.println();
}
void loop()
{
ds18process(); //call this every loop itteration, the more calls the better.
if(millis() > nextprint) {
Serial.print("Temp F: ");
for(byte j=0; j<nsensors; j++){
Serial.print(j); Serial.print("=");
Serial.print(ds18temp(1, tempraw[j])); Serial.print(" ");
}
Serial.println();
nextprint = millis() + 1000; //print once a second
}
}
/* Process the sensor data in stages.
* each stage will run quickly. the conversion
* delay is done via a millis() based delay.
* a 5 second wait between reads reduces self
* heating of the sensors.
*/
void ds18process() {
static byte stage = 0;
static unsigned long timeNextStage = 0;
static byte sensorindex = 100;
byte i, j;
byte present = 0;
byte type_s;
byte data[12];
byte addr[8];
if(stage == 0 && millis() > timeNextStage) {
if (!ds.search(addr)) {
//no more, reset search and pause
ds.reset_search();
timeNextStage = millis() + 100; //1/10 of a second
return;
} else {
if (OneWire::crc8(addr, 7) != addr[7]) {
Serial.println("CRC is not valid!");
return;
}
//got one, start stage 1
stage = 1;
}
}
if(stage==1) {
Serial.print("ROM =");
for ( i = 0; i < 8; i++) {
Serial.write(' ');
Serial.print(addr[i], HEX);
}
//find sensor
for(j=0; j<nsensors; j++){
sensorindex = j;
for(i=0; i<8; i++){
if(sensors[j][i] != addr[i]) {
sensorindex = 100;
break; // stop the i loop
}
}
if (sensorindex < 100) {
break; //found it, stop the j loop
}
}
if(sensorindex == 100) {
Serial.println(" Sensor not found in array");
stage = 0;
return;
}
Serial.print(" index="); Serial.println(sensorindex);
ds.reset();
ds.select(sensors[sensorindex]);
ds.write(0x44, 0); // start conversion, with parasite power off at the end
stage = 2; //now wait for stage 2
timeNextStage = millis() + 1000; //wait 1 seconds for the read
}
if (stage == 2 && millis() > timeNextStage) {
// the first ROM byte indicates which chip
switch (sensors[sensorindex][0]) {
case 0x10:
Serial.print(" Chip = DS18S20"); // or old DS1820
Serial.print(" index="); Serial.println(sensorindex);
type_s = 1;
break;
case 0x28:
Serial.print(" Chip = DS18B20");
Serial.print(" index="); Serial.println(sensorindex);
type_s = 0;
break;
case 0x22:
Serial.print(" Chip = DS1822");
Serial.print(" index="); Serial.println(sensorindex);
type_s = 0;
break;
default:
Serial.println("Device is not a DS18x20 family device.");
stage=0;
return;
}
present = ds.reset();
ds.select(sensors[sensorindex]);
ds.write(0xBE); // Read Scratchpad
Serial.print(" Data = ");
Serial.print(present, HEX);
Serial.print(" ");
for ( i = 0; i < 9; i++) { // we need 9 bytes
data[i] = ds.read();
Serial.print(data[i], HEX);
Serial.print(" ");
}
Serial.print(" CRC=");
Serial.print(OneWire::crc8(data, 8), HEX);
Serial.print(" index="); Serial.print(sensorindex);
Serial.println();
int16_t 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);
// at lower res, the low bits are undefined, so let's zero them
if (cfg == 0x00) raw = raw & ~7; // 9 bit resolution, 93.75 ms
else if (cfg == 0x20) raw = raw & ~3; // 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
}
tempraw[sensorindex] = raw;
stage=0;
}
}
/* Converts raw temp to Celsius or Fahrenheit
* scale: 0=celsius, 1=fahrenheit
* raw: raw temp from sensor
*
* Call at any time to get the last save temperature
*/
float ds18temp(byte scale, int16_t raw)
{
switch(scale) {
case 0: //Celsius
return (float)raw / 16.0;
break;
case 1: //Fahrenheit
return (float)raw / 16.0 * 1.8 + 32.0;
break;
default: //er, wut
return -255;
}
}
I am having trouble deciphering how this code works (new to Arduino). I am specifically wondering what the line OneWire ds(2) does, and what this means for the step of my circuit. What do I need to connect to pin 2?
