Hi,
I am currently working on making an emulated temperature sensor (DS18B20) by using arduino uno. I found a library that seems to work.
The emulated sensor can be read when it is connected to another arduino with a code that reads onewire devices. Below is the code:
#include <OneWire.h>
// OneWire DS18S20, DS18B20, DS1822 Temperature Example
//
// http://www.pjrc.com/teensy/td_libs_OneWire.html
//
// The DallasTemperature library can do all this work for you!
// http://milesburton.com/Dallas_Temperature_Control_Library
OneWire ds(15); // on pin 10 (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)) {
Serial.println("No more addresses.");
Serial.println();
ds.reset_search();
delay(250);
return;
}
Serial.print("ROM =");
for( i = 0; i < 8; i++) {
Serial.write(' ');
Serial.print(addr[i], HEX);
}
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:
Serial.println(" Chip = DS18S20"); // or old DS1820
type_s = 1;
break;
case 0x28:
Serial.println(" Chip = DS18B20");
type_s = 0;
break;
case 0x22:
Serial.println(" Chip = DS1822");
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); // maybe 750ms is enough, maybe not
// we might do a ds.depower() here, but the reset will take care of it.
present = ds.reset();
ds.select(addr);
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.println();
// Convert the data to actual temperature
// because the result is a 16 bit signed integer, it should
// be stored to an "int16_t" type, which is always 16 bits
// even when compiled on a 32 bit processor.
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
}
celsius = (float)raw / 16.0;
fahrenheit = celsius * 1.8 + 32.0;
Serial.print(" Temperature = ");
Serial.print(celsius);
Serial.print(" Celsius, ");
Serial.print(fahrenheit);
Serial.println(" Fahrenheit");
}
However, when it is connected to Teltonika FM1120 device's onewire data pin ( pin 8 ) together with common ground, it does not show any readings at the server.
http://plantron.gr/sites/plantron.gr/files/pdf/FM1120%20User%20Manual%20v1.12.pdf
Below is my emulated sensor code:
#include "OneWireHub.h"
#include "DS18B20.h" // Dual channel addressable switch
#define OneWire_PIN 9
OneWireHub * hub = 0;
DS18B20 * fMS;
float temp = 0;
void setup() {
// Debug
Serial.begin(9600);
// Work - Digital Thermometer
fMS = new DS18B20( 0x28, 0xFC, 0x00, 0x49, 0x35, 0x32, 0x12 );
// Setup OneWire
hub = new OneWireHub( OneWire_PIN );
hub->elms[0] = fMS;
hub->calck_mask();
}
void loop() {
// Set temp
fMS->settemp(10);
// put your main code here, to run repeatedly:
hub->waitForRequest(false);
}
I have also taken an oscillogram when the Teltonika device is connected to the emulated sensor; also when the emulated sensor is connected to the arduino reader ( reads onewire devices ).
Emulated sensor to arduino reader:
Emulated sensor to Teltonika device:
It seems that the emulated sensor is not sending the presence pulse after the Teltonika device has sent the reset pulse. Any ideas or comments? Thanks in advance.
OneWireHub.cpp (22.3 KB)
OneWireHub.h (2.24 KB)
DS18B20.h (320 Bytes)
DS18B20.cpp (2.67 KB)
