[AVR] Reading DS18B20 chip ?

[bianchi77]

Guys,

I tried to read DS18B20...
but the output in USART is

Temperature : ?

What should I change in this code ? thanks

char printbuff[100];
	double d = 0;
	int d1 = d; 
		
	usart_init(BAUD_PRESCALE);
	usart_pstr("TEST DS18B20 \n" );
	//init interrupt
	sei();
	
	while(1)
	{
		d = ds18b20_gettemp();
		//printf(printbuff,"%d",d1);
		
		sprintf(printbuff, "%.2f", d);
		usart_pstr("Temperature:");
		usart_pstr(printbuff);
		usart_pstr("\r\n");
		_delay_ms(500);
		
	}

 

[Easyrider83]

Possible, start converion command missed? Also, delay 750ms needed for conversion.

 

[mikewardlow]

Attached is a Windows Liberty Basic program the uses the LinkUSB adapter
perhaps you can get some idea from it...

 

[mikewardlow]

Attached is a Windows Liberty Basic program the uses the LinkUSB adapter
perhaps you can get some idea from it...

adding attachment

low level send rom address or skip rom - must select device
send convert cmd wait 750 ms if in parasite mode
send read scratch pad to get values
process the values

does you hi level get-temperature
does your hilevel support the adapter you are using, I use LinkUSB [DS9097U]

 

[betwixt]

It depends on what the function "ds18b20_gettemp()" does and whether it includes all the delays and commands needed for the device to return a value.

You are assigning the result to a double so printing it as a float wont work!

Brian.