Author: RickardP

I was looking into how to make a small cost wifi temperature sensor and i find WeMos D1 mini Pro as a very little arduino with wifi on it.

So i buy two of them + two 1-wire temperature sensors DS18S20 and starting read about and after a while testing i got the temperature sensor to work.

The code i used to get the temperature sensor values was:
#include <OneWire.h>

// OneWire DS18S20, DS18B20, DS1822 Temperature Example

OneWire ds(D4); // on pin D4 (a 4.7K resistor is necessary)

void setup(void)
{
Serial.begin(9600);
}

void loop(void)
{
byte i;
byte present = 0;
byte type_s;
byte data[12];
byte addr[8];
float celsius, fahrenheit;

if ( !ds.search(addr))
{
ds.reset_search();
delay(250);
return;
}


if (OneWire::crc8(addr, 7) != addr[7])
{
Serial.println("CRC is not valid!");
return;
}
Serial.println();

// the first ROM byte indicates which chip
switch (addr[0])
{
case 0x10:
type_s = 1;
break;
case 0x28:
type_s = 0;
break;
case 0x22:
type_s = 0;
break;
default:
Serial.println("Device is not a DS18x20 family device.");
return;
}

ds.reset();
ds.select(addr);
ds.write(0x44, 1); // start conversion, with parasite power on at the end
delay(1000);
present = ds.reset();
ds.select(addr);
ds.write(0xBE); // Read Scratchpad

for ( i = 0; i < 9; i++)
{
data[i] = ds.read();
}

// Convert the data to actual temperature
int16_t raw = (data[1] << 8) | data[0];
if (type_s) {
raw = raw << 3; // 9 bit resolution default
if (data[7] == 0x10)
{
raw = (raw & 0xFFF0) + 12 - data[6];
}
}
else
{
byte cfg = (data[4] & 0x60);
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

}

celsius = (float)raw / 16.0;

Serial.print(" Temperature = ");
Serial.print(celsius);
Serial.print(" Celsius ");

}