Tilpasset DS18B20 Sensorsonde & 1-Wire Cable Assembly

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The DS18B20 sensor communicates using the “1-Wire” protocol, which means it uses a single data line for all communication with a microcontroller, allowing multiple sensors to be connected on the same line and identified by their unique 64-bit serial code; this single data line is pulled high with a resistor and the sensor transmits data by pulling the line low during specific time slots to send bits of information.

DS18B20 temperatursensor: The DS18B20 waterproof probe is designed for underwater use, capable of operating in wet or moist environments without being damaged by water or moisture.
Temperature sensor supply voltage: 3.0V ~ 5.25V;
Operating temperature range:-55 ℃ til +125 ℃ (-67 ℉ to +257 ℉);
Provides from 9-bit to 12-bit Celsius temperature measurements;
Adapter module is equipped with a pull-up resistor, and directly connects to the GPIO of the Raspberry Pi without an external resistor;
Use this adapter module kit to simplify connecting the waterproof temperature sensor to your project.

DS18B20 digital temperature sensor probe & XH2.54 to PH2.0 module

China-made DS18B20 chip temperature acquisition TO-92 temperature sensor

DS18B20 temperature sensor 1-wire waterproof cable + adapter board set

1. Key points about the 1-Wire protocol:
Single data line:
Only one wire is needed for communication between the sensor and the microcontroller.
Half-duplex communication:
Data can be sent in both directions, but only one direction at a time.
Parasite power:
The DS18B20 can be powered directly from the data line during communication, eliminating the need for a separate power supply in some cases.
Unique device addresses:
Each DS18B20 sensor has a unique 64-bit serial code that allows the microcontroller to identify and address individual sensors on the bus.
Communication steps with a DS18B20:
1.1 Reset pulse:
The microcontroller initiates communication by pulling the data line low for a specific duration (reset pulse).
1.2 Presence pulse:
If a DS18B20 is present on the bus, it will respond with a short pulse, indicating its presence.
1.3 ROM command:
The microcontroller sends a ROM command to either read the unique 64-bit code of a specific sensor (“Match ROM”) or to address all sensors on the bus (“Skip ROM”).
1.4 Function command:
Depending on the desired operation (like reading temperature), the microcontroller sends a specific function command to the sensor.
1.5 Data transfer:
Data is transmitted bit-by-bit, with the sensor pulling the data line low to send a ‘0’ and letting the line go high to send a ‘1’.

2. Detaljert forklaring av DS18B20s 1-Wire kommunikasjonsprotokoll
Årsaken til at DS18B20 -sensorer er mye brukt skyldes i stor grad den unike kommunikasjonsprotokollen – 1-Ledningskommunikasjonsprotokoll. Denne protokollen forenkler kravene til maskinvareforbindelser og gir en effektiv måte å overføre data. Dette kapittelet vil dypt analysere arbeidsmekanismen og datautvekslingsprosessen for 1-linjers kommunikasjonsprotokoll for å legge et solid grunnlag for påfølgende programmeringspraksis.
2.1 Grunnleggende om 1-tråds kommunikasjonsprotokoll
2.1.1 Funksjoner i 1-tråds kommunikasjonsprotokoll:
DS18B20 1-tråd kommunikasjonsprotokoll kalles også “enkeltbuss” teknologi. Den har følgende funksjoner: – Enkeltbusskommunikasjon: Bare en datalinje brukes til toveis dataoverføring, Noe som reduserer kompleksiteten i ledningene sammenlignet med den tradisjonelle kommunikasjonsmetoden for flere trådføler. – Forbindelse med flere enheter: Støtter tilkobling av flere enheter på en databuss, og identifiserer og kommuniserer gjennom enhetens identifikasjonskoder. – Lavt strømforbruk: Under kommunikasjon, enheten kan være i en lav effekt standby-tilstand når du ikke deltar i kommunikasjon. – Høy presisjon: Med en kortere dataoverføringstid, Det kan redusere ekstern interferens og forbedre datatøyaktigheten.
2.1.2 Dataformat og timinganalyse av 1-tråds kommunikasjon
Dataformatet til 1-Wire Communication Protocol følger en spesifikk tidsregel. Det inkluderer initialiseringstiming, Skriv timing og les timing:
Initialiseringstiming: Verten starter først tilstedeværelsesdeteksjonstimingen (Tilstedeværelsespuls) ved å trekke ned bussen i en viss periode, og sensoren sender deretter en tilstedeværelsespuls som svar.
Skriv timing: Når verten sender en skrivetidspunkt, Den trekker først bussen i omtrent 1-15 mikrosekunder, slipper deretter bussen, og sensoren trekker ned bussen i 60-120 Mikrosekunder for å svare.
Les timing: Verten varsler sensoren om å sende data ved å trekke ned bussen og slippe den, og sensoren vil sende ut databiten på bussen etter en viss forsinkelse.

Analog Devices DS18B20+, MAXIM Programmable Resolution 1-Wire Digital Thermometer

DS18B20 12-bit 1-Wire Digital Temperature Sensor w/ 1 Meter Cable

DS18B20 sensor probe dedicated to temperature and humidity collection in cold chain cold storage

2.2 Software implementation of data communication
2.2.1 Initialization and reset of 1-line communication
At the software level, initialization and reset of 1-Wire communication is the first step of communication. The following is the pseudo code to implement this process:

// OneWire communication initialization function
void OneWire_Init() {
// Set the bus to input mode and enable the pull-up resistor
SetPinMode(DS18B20_PIN, INPUT_PULLUP);
// Wait for the bus to be idle
DelayMicroseconds(1);
// Send a reset pulse
OneWire_Reset();
}

// OneWire communication reset function
void OneWire_Reset() {
// Pull down the bus
SetPinMode(DS18B20_PIN, OUTPUT_LOW);
DelayMicroseconds(480);
// Release the bus
SetPinMode(DS18B20_PIN, INPUT_PULLUP);
DelayMicroseconds(70);
// Wait for the presence of a pulse
hvis (!WaitForOneWirePresence())
// No pulse was detected, maybe the sensor is not connected or the initialization failed
HandleError();
DelayMicroseconds(410);
}

// Waiting for the presence of a pulse
bool WaitForOneWirePresence() {
return ReadPin(DS18B20_PIN) == 0; // Assume low level is a signal presence
}

2.2.2 Data reading and writing operations

Data reading and writing operations are the core part of sensor communication. The following code shows how to write a byte to a one-wire bus:
// Write a byte to a one-wire bus
void OneWire_WriteByte(byte data) {
for (int i = 0; i < 8; i++) {
OneWire_WriteBit(data & 0x01);
data >>= 1;
}
}

// Write a bit to a one-wire bus
void OneWire_WriteBit(bit data) {
SetPinMode(DS18B20_PIN, OUTPUT_LOW);
hvis (data) {
// Release the bus when writing 1
SetPinMode(DS18B20_PIN, INPUT_PULLUP);
DelayMicroseconds(1);
} ellers {
// Continue to pull the bus low when writing 0
DelayMicroseconds(60);
}
SetPinMode(DS18B20_PIN, INPUT_PULLUP);
DelayMicroseconds(1);
}

Next is the function to read a byte:
// Read a byte from the one-wire bus
byte OneWire_ReadByte() {
byte data = 0;
for (int i = 0; i < 8; i++) {
data >>= 1;
hvis (OneWire_ReadBit())
data |= 0x80;
}
return data;
}

// Read a bit from the one-wire bus
bit OneWire_ReadBit() {
SetPinMode(DS18B20_PIN, OUTPUT_LOW);
SetPinMode(DS18B20_PIN, INPUT_PULLUP);
DelayMicroseconds(3);
bool result = ReadPin(DS18B20_PIN);
DelayMicroseconds(57);
return result;
}

2.2.3 Verification mechanism of OneWire communication

The OneWire communication protocol uses a simple verification mechanism in the data exchange process, usually by reading back the written data to verify the correctness of the data. The following is a sample code for verifying the written data:

byte data = 0x55; // Assume that the data to be sent

OneWire_WriteByte(data); // Write data to the OneWire bus

byte readData = OneWire_ReadByte(); // Read back data from the OneWire bus

hvis (readData != data) {
HandleError(); // If the read-back data does not match the written data, handle the error