problem with ZUNO_DS18B20 with sub zero temperatures

[mzagula78]

Hello,

I used example code provided for Z-UNO. Everything works fine when measuring positive temperatures.
But with freezing temperatures I noticed results are not correct.

Either library ZUNO_DS18B20 has not correct logic to convert temperatures or it is lacking it and I am supposed to add some transformation to get correct negative temperatures? Please advise.

Normally values returned by sensor I am multiplying by 100 as per the rules on your website. But for negative temperatures it doesn't seem to work.
Unless I mixed up sizes/precision for calculation. But I have size 2 and precision 2 for SENSOR MULTILEVEL. I think I am not even getting there as the value returned by sensor doesn't fit. So, I suspect Library has a problem to convert it correctly.

https://z-uno.z-wave.me/Reference/ZUNO_ ... ULTILEVEL/

Values returned by getter are signed. Values are interpreted according to the following transformation:
signed value = value / 10precision, for value < MAX_NUM/2
signed value = (value - MAX_NUM) / 10precision, for value ≥ MAX_NUM/2
Where MAX_NUM = 28*size and precision defined number of decimal digits after dot.
For example if size 1 and precision 0, value 25 represents 25,
for size 1 and precision 0, value 164 represents -92 = 164 - 256,
for size 1 and precision 1, value 25 represents 2.5 = 25 / 10,
for size 1 and precision 1, value 164 represents -9.2 = (164 - 256) / 10,
for size 2 and precision 1, value 366 represents 36.6,
for size 2 and precision 1, value 65535 represents -0.1 = (65535 - 65536) / 10,
for size 2 and precision 2, value 65535 represents -0.01 = (65535 - 65536) / 100.



my code below and I tried adjusting resolutions etc but nothing works

// demo sketch for connecting OneWire temperature sensor DS18B20 to Z-Uno

// add library ds18b20
#include <ZUNO_DS18B20.h>
#include <ZUNO_OneWire.h>

// pin connection ds18b20
#define PIN_DS18B20 11
#define N_SENSOR 1
#define MAX_NUM 65536
#define MAX_NUM2 32768

OneWire ow(PIN_DS18B20);

// onewire connection temperature sensors
DS18B20Sensor ds1820(&ow);

byte addr1[8];
word temp; // Here we store temperatures
float value;
word paramValue;
word resolution

ZUNO_SETUP_CFGPARAMETER_HANDLER(config_parameter_changed);


// ZUNO_SETUP_SLEEPING_MODE(ZUNO_SLEEPING_MODE_FREQUENTLY_AWAKE);
// set up channel
ZUNO_SETUP_CHANNELS(
ZUNO_SENSOR_MULTILEVEL(ZUNO_SENSOR_MULTILEVEL_TYPE_TEMPERATURE,
SENSOR_MULTILEVEL_SCALE_CELSIUS,
SENSOR_MULTILEVEL_SIZE_TWO_BYTES,
SENSOR_MULTILEVEL_PRECISION_TWO_DECIMALS,
getterTemp)

);

void setup() {
Serial.begin(9600);
Serial.println("start");

// paramValue = zunoLoadCFGParam(11);
}

//void config_parameter_changed(byte param, word value) {
// if (param == 11) { // The first user-defined parameter
// paramValue = 60;
// }
//}

void loop() {

// word value = zunoLoadCFGParam(byte param);
// zunoSaveCFGParam(11, paramValue);
delay(30000);
ds1820.scanAloneSensor(addr1);
// obtaining readings from the sensor ds18b20
float temerature = ds1820.getTemperature(addr1);
// float temerature = ds1820.getTempC100(addr1);
resolution = ds1820.getResolution();
ds1820.setResolution(2,NULL);
Serial.print("Your resolution is: ");
Serial.println(resolution);
// make scaled word value for report
// temp=int(temerature*10);

Serial.print("Your sensor address is: ");
for(byte i = 0; i < 1; i++) {
// print OneWire code
Serial.print(addr1, HEX);
Serial.print(" ");

// value = (float)temerature/16;
value = temerature;
if (value < MAX_NUM2) {
temp = float(value*100);
} else {
temp = float((value - MAX_NUM)/100);
}

// temp = float(temerature*100);
// temp = -500;
Serial.print("Temp: ");
Serial.println(temp);
// zunoSendReport(1);
}
Serial.println();

Serial.print("Temperature: ");
Serial.println(temerature);
Serial.print("Temp: ");
Serial.println(temp);
Serial.print("value: ");
Serial.println(value);

// send data to channel
zunoSendReport(1);
// send every 30 second
// delay(100);
// zunoSetBeamCountWU(30);
// zunoSendDeviceToSleep();
}

word getterTemp() {
return temp;
}

[mzagula78]

I tried 2 different sensors and result is the same. Will try to test it on regular arduino board with classic OneWire andDS18B20/Dallas/etc libraries.
When temperature measured is below zero it only gives some value always something like 4089 or 4098 which is rounded to 4.1.
This is output from library function getTempC100. So, whatever goes to zwave channels is returned correctly in Smartthings.
Problem is how this is calculated.