Reading a digital signal and DAC.

Hi,

I am currently trying to convert a digital signal to an analogue signal using DUE.
I have connected DS18B20 (A digital sensor) to Due.

const int digitalInputPin = 26;

void setup() {
pinMode (DAC1,OUTPUT);
pinMode (digitalInputPin,INPUT);
Serial.begin(9600);

}

void loop() {

int b;

for(int i=0; i<4096; i++)
{
b = digitalRead (digitalInputPin);// Read pin 26

analogWriteResolution(12); //12 bits resolution
analogWrite(DAC1, i); // output values of varible b at the Digial to analog converter
delayMicroseconds(14);
Serial.println (b);
}
while(0){ // loop goes forever
}

}

Will this code change the digital signal from the sensor and output analog signal according to temperature change?

Any help will be greatly appreciated.

Thank you

Yong

analogWrite(DAC1, i); // output values of varible b at the Digial to analog converter

Well, there's no mention of "b" in the program statement, so I don't think you'll get anything related to b on the DAC output. You might get a nice ramp as i goes from 0 to 4096.

b = digitalRead (digitalInputPin);// Read pin 26 (I have connected DS18B20)

digitalRead() returns a digital single-bit value; the digital STATE of the particular pin. The DS18B20 is a sensor that reads the temperatures and sends the result using a SEQUENCE of bit transitions, NOT a single bit. you'll want to use a library that can handle chip, or at least the sequencing of the bits. There happens to be one here: Dallas Temperature Control Library - Miles Burton - Innovative engineering for pretty much anything (Hmm. I don't know whether this works on Due.)

Thank you for your reply!
That is the issue I am having for a while and I just don’t know how to go on about it.
I tried another method which was using Arduino Uno, MCP4725(DAC) and MCP9808(A digital temperature sensor).

The code below gives the data value in Hex.
Could you possibly explain a little more on this?

Thank you!

#include <OneWire.h>

OneWire ds(2); // on pin 2 (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*, 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 0x28:*

  • Serial.println(" Chip = DS18B20");*

  • type_s = 0;*

  • break;*

  • default:*

  • Serial.println(“Device is not a DS18x20 family device.”);*

  • return;*

  • }*

  • ds.reset();*

  • ds.select(addr);*

  • ds.write(0x44); // start conversion, use ds.write(0x44,1) 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 = ds.read();_
    _ Serial.print(data*, 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");
    }
    ROM = 28 88 84 82 5 0 0 6A
    Chip = DS18B20*
    * Data = 1 51 1 4B 46 7F FF F 10 FE CRC=FE*
    * Temperature = 21.06 Celsius, 69.91 Fahrenheit*_