Default DS18S20 example returns perplexing results

greetings,

i beginning play dallas semiconductor ds18s20 , onewire library , out of gate seeing strange results.

i using default temperature sensor example. i'm connecting single ds18s10 pin 10 of leonardo 4.7k pullup resistor, not using parasitic power. sketch compiles, uploads, , runs fine either arduino 1.0.5 or 1.5.7 on mac os x mavericks. seems see ds18s20 , extract serial number, seems pass crc check. temperatures negative territory. respond temperature changes, it's clear data being read, not interpreted correctly.

at first blush i'd guess there byte order problem or byte misalignment or of type, without proper debugger i'm stabbing in dark. there peculiar arduino on mac perhaps missed when library made? best googling skills not helping.

here's output few runs sensor between fingers raise temperature.

code: [select]


rom = 10 3d ae 62 0 8 0 2c
 chip = ds18s20
 data = 1 ff 0 0 ff ff c 10 38  crc=38
 temperature = -33.00 celsius, -27.40 fahrenheit
no more addresses.

rom = 10 3d ae 62 0 8 0 2c
 chip = ds18s20
 data = 1 c0 ff 0 0 ff ff f 10 61  crc=61
 temperature = -32.19 celsius, -25.94 fahrenheit
no more addresses.

rom = 10 3d ae 62 0 8 0 2c
 chip = ds18s20
 data = 1 c1 ff 0 0 ff ff 1 10 fe  crc=fe
 temperature = -31.31 celsius, -24.36 fahrenheit
no more addresses.

rom = 10 3d ae 62 0 8 0 2c
 chip = ds18s20
 data = 1 c3 ff 0 0 ff ff 7 10 d2  crc=d2
 temperature = -30.69 celsius, -23.24 fahrenheit
no more addresses.

rom = 10 3d ae 62 0 8 0 2c
 chip = ds18s20
 data = 1 c4 ff 0 0 ff ff f 10 74  crc=74
 temperature = -30.19 celsius, -22.34 fahrenheit
no more addresses.

rom = 10 3d ae 62 0 8 0 2c
 chip = ds18s20
 data = 1 c4 ff 0 0 ff ff 10 8b  crc=8b
 temperature = -29.87 celsius, -21.77 fahrenheit
no more addresses.

the example code:

code: [select]

#include <onewire.h>

// onewire ds18s20, ds18b20, ds1822 temperature example
//
// http://www.pjrc.com/teensy/td_libs_onewire.html
//
// dallastemperature library can work you!
// http://milesburton.com/dallas_temperature_control_library

onewire  ds(10);  // on pin 10 (a 4.7k resistor 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( = 0; < 8; i++) {
    serial.write(' ');
    serial.print(addr[i], hex);
  }

  if (onewire::crc8(addr, 7) != addr[7]) {
      serial.println("crc not valid!");
      return;
  }
  serial.println();

  // first rom byte indicates 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 not ds18x20 family device.");
      return;
  }

  ds.reset();
  ds.select(addr);
  ds.write(0x44, 1);        // start conversion, parasite power on @ end
 
  delay(1000);     // maybe 750ms enough, maybe not
  // might ds.depower() here, reset take care of it.
 
  present = ds.reset();
  ds.select(addr);   
  ds.write(0xbe);         // read scratchpad

  serial.print("  data = ");
  serial.print(present, hex);
  serial.print(" ");
  ( = 0; < 9; i++) {           // 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 data actual temperature
  // because result 16 bit signed integer, should
  // stored "int16_t" type, 16 bits
  // when compiled on 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);
    // @ lower res, low bits undefined, let's 0 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 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");
}

please post code, using code tags ("#" button).

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