ESP32 NodeMCU Interface DS1B20

The DS18B20 is a digital temperature sensor that communicates over a 1-Wire interface, meaning multiple sensors can be connected to the same data pin. It provides 9–12 bit temperature readings in Celsius, with a range of -55°C to +125°C and ±0.5°C accuracy.

Key Features:

• Digital output – No analog-to-digital conversion required.
• Unique 64-bit address – Allows multiple sensors on the same bus.
• Power options – Can operate with external VCC or parasite power (powered through data line).
• High resolution – 9–12 bits configurable (0.5°C to 0.0625°C per step).
• Low cost and widely available

Procedure

1. Initialize 1-Wire bus.
2. Search for DS18B20 sensors.
3. Verify CRC and family code.
4. Start temperature conversion (0x44).
5. Read scratchpad (0xBE).
6. Convert raw data to Celsius and print.

DS18B20 is popular in embedded systems due to its simplicity, accuracy, and ability to connect multiple sensors. Common applications include:

Applications

1. Home Automation & IoT
   • Smart thermostats
   • Room temperature monitoring
   • Automated HVAC systems
2. Industrial Monitoring
   • Process temperature control
   • Refrigeration units and cold storage monitoring
   • Greenhouse temperature tracking
3. Embedded Projects
   • Arduino/ESP32 based weather stations
   • Temperature logging with SD card or cloud
   • Multi-sensor arrays using one data pin
4. Consumer Electronics
   • Water heaters and coffee machines
   • Appliances requiring precise temperature feedback

 

Code of ESP32 NodeMCU Interface DS1B20

Onewire – DS18bB20 Sensor interface

pin = 23
ow.setup(pin)
count = 0
repeat
  count = count + 1
  addr = ow.reset_search(pin)
  addr = ow.search(pin)
until (addr ~= nil) or (count > 100)
if addr == nil then
  print("No more addresses.")
else
  print(addr:byte(1,8))
  crc = ow.crc8(string.sub(addr,1,7))
  if crc == addr:byte(8) then
    if (addr:byte(1) == 0x10) or (addr:byte(1) == 0x28) then
      print("Device is a DS18S20 family device.")
        repeat
          ow.reset(pin)
          ow.select(pin, addr)
          ow.write(pin, 0x44, 1)
        --  tmr.delay(1000000)
          present = ow.reset(pin)
          ow.select(pin, addr)
          ow.write(pin,0xBE,1)
          print("P="..present)  
          data = nil
          data = string.char(ow.read(pin))
          for i = 1, 8 do
            data = data .. string.char(ow.read(pin))
          end
          print(data:byte(1,9))
          crc = ow.crc8(string.sub(data,1,8))
          print("CRC="..crc)
          if crc == data:byte(9) then
             t = (data:byte(1) + data:byte(2) * 256) * 625
             t1 = t / 10000
             t2 = t % 10000
             print("Temperature="..t1.."."..t2.."Centigrade")
          end                   
        until false
    else
      print("Device family is not recognized.")
    end
  else
    print("CRC is not valid!")
  end
end

 

Setup

pin = 23
ow.setup(pin)

• pin = 23 → GPIO 23 is used for the DS18B20 data line.
• ow.setup(pin) → Initializes the 1-Wire bus on that pin.

---

Searching for 1-Wire Devices

count = 0
repeat
  count = count + 1
  addr = ow.reset_search(pin)
  addr = ow.search(pin)
until (addr ~= nil) or (count > 100)

• Searches for devices connected to the 1-Wire bus.
• Loops up to 100 times until a device address is found.

if addr == nil then
  print("No more addresses.")
else
  print(addr:byte(1,8))

• Prints the 8-byte address of the device if found.

---

CRC Check

crc = ow.crc8(string.sub(addr,1,7))
if crc == addr:byte(8) then

• Calculates CRC of the first 7 bytes of the address.
• Validates if the device address is correct (prevents communication errors).

---

Device Type Check for ESP32 NodeMCU Interface DS1B20

if (addr:byte(1) == 0x10) or (addr:byte(1) == 0x28) then
  print("Device is a DS18S20 family device.")

• DS18S20 family uses 0x10 or 0x28 as family codes.

---

Reading Temperature

ow.reset(pin)
ow.select(pin, addr)
ow.write(pin, 0x44, 1)  -- Start temperature conversion

• Sends Convert T command (0x44) to the sensor.
• Sensor measures temperature (takes ~750ms for 12-bit resolution).

present = ow.reset(pin)
ow.select(pin, addr)
ow.write(pin,0xBE,1)  -- Read scratchpad

• Sends Read Scratchpad command (0xBE) to read temperature data.

data = string.char(ow.read(pin))
for i = 1, 8 do
  data = data .. string.char(ow.read(pin))
end

• Reads 9 bytes from the sensor’s scratchpad (includes temperature and CRC).

---

Temperature Conversion

t = (data:byte(1) + data:byte(2) * 256) * 625
t1 = t / 10000
t2 = t % 10000
print("Temperature="..t1.."."..t2.."Centigrade")

• Combines LSB and MSB to get raw temperature.
• Multiplies by 0.0625 (represented here as 625 / 10000) to convert to Celsius.