I am having serious issues with my code when trying to access the DS18S20 probes.
Once I think I got it and get proper readouts, I start changing the next thing and suddenly my sketch freezes after getting the first temperature.
So I think "well, I coded something wrong", but when I comment out the call to the method that is reading the OneWire bus, everything runs smoothly. So I would appreciate if someone would have a look at what is happening in this method:
First of all, the following method scans for probes on the bus and saves their address into a 2-dimensional array probes[][]
void scanAllProbes()
{
probespresent = 0;
ds.reset_search();
while(probespresent < 8 && ds.search(addr))
{
if ( addr[0] != 0x10 && addr[0] != 0x28 )
{
output("Unknown","probe");
}
else
{
String address = "";
for(int i = 0; i < 8; i++)
{
probes[probespresent][i] = addr[i];
address += String(addr[i],HEX);
}
output("Found probe:", address);
probespresent++;
}
delay(1000);
}
//probespresent now contains the number of probes connected
}
void getTemperature()
{
if(lastRequestTimestamp == 0) //no request done yet
{
for(int i = 0; i < probespresent; i++)
{
ds.reset();
ds.select(probes[i]);
ds.write(0x44,1); // start conversion, with parasite power on at the end
temp[i] = 0;
}
lastRequestTimestamp = millis();
return;
}
//check if last temperature request was over 5 sec ago
if( (millis() - lastRequestTimestamp) >= 5000 )
{
//now data should be present for each probe
average = 0;
for(int i = 0; i < probespresent; i++)
{
byte data[12];
ds.reset();
//select each connected probe
ds.select(probes[i]);
ds.write(0xBE);
for(int j = 0; j < 9; j++)
{
data[j] = ds.read();
}
byte MSB = data[1];
byte LSB = data[0];
temp[i] = ((MSB << 8) | LSB) / 16; //using two's compliment
average += temp[i];
}
average = average / max(probespresent,1);
//now make another request
for(int i = 0; i < probespresent; i++)
{
ds.reset();
ds.select(probes[i]);
ds.write(0x44,1); // start conversion, with parasite power on at the end
}
//set the timestamp to current time
lastRequestTimestamp = millis();
}
}
The getTemperature-Method is executed on each iteration of loop() and places a request. On consecutives runs, no further action is taken until 5 seconds have passed since the last request, then it tries to retrieve the values from the scratchpad, save them into an array and calculate the average temperature. After that, a new request is placed and the timestamp saved.
I cannot see any problem with that, but if I output the temperature after each run of getTemperature, I get
1st run Probe 1: 0, Probe 2: 0, average 0
2nd run Probe 1: 24, Probe 2: 0, average 12 and the program freezes.
So it is actually not getting/writing the temperature from the second probe but goes on outputting the value
Then somewhere in the 3rd run it is freezing...
Any ideas about what's going wrong here?
