Matrix user forums

Posted: **Tue Mar 01, 2011 5:15 am**

In the datasheet of the DS1820 it's stated that the data of the master is send, LSB first.
Does the 1-wire component work this way? Does it always send and receives it's data LSB first?

There are macro's for the 1-wire component in Flowcode that handle the data flow to and from the DS1820, but I want to use this temperature sensor in a different way.
If I use the examples from the datasheet I get a weird response in my logic analyser.

Maybe strange, but let's say I need to send 48h and the direction is wrong, (when I use the oo_TX_byte macro), do I need to send 12h instead? 12h is 48h in the other direction.

Posted: **Tue Mar 01, 2011 9:15 am**

Hello,

The "oo_tx_byte" function always sends its data out with the least significant bit first so you do not have to do any manipulation on the data you are sending.

Posted: **Tue Mar 01, 2011 2:56 pm**

Thank you BenJ.

I will keep trying

Posted: **Tue Mar 01, 2011 3:04 pm**

The 1-wire component uses delays so you may want to check that your configuration and clock speed settings are correct in Flowcode otherwise the component will not work correctly. A 1 second flasher program will confirm if you have everything set up correctly.

Also 1-wire requires an external pull up resistor to be fitted to the 1-wire signal wire. I think the value of the pull up may vary depending on the length of your bus and the number of devices connected.

Posted: **Tue Mar 01, 2011 6:52 pm**

Dear BenJ.

I can read the temperature when I use the DS1820 macro's.
That works fine.

I just want to read the bits of the scratchpad myself.
In the datasheet there are examples of how to address the DS1820

When I try to implement them myself with the oo_TX and the oo_RX macro's they don't work.
In the datasheet I find that first a reset, followed by a presence puls is the start.
Then a SEARCH ROM (0xF0) would return the 64bit ROM code of the DS1820.

When I issue a oo_busreset followed by a oo_ScanBus macro, I see this

Reset, presence,error,unknown,reset,presence,0XFO and then strange 24 * 8 bits.
Normally the 0XF0 should be followed by 64bits?

Strange, not what I expected.
Is there something more Matrix does in it's macro's?
The part where the line is pulled down (= ERROR) approx 620µs, followed by 620µs high (= unknown), where does this come from?

Why does the bus contain 24byte instead of 64bits?
The DS1820 family code in the ROM (10h) is nowhere to be found..

Strange :-s

Posted: **Wed Mar 02, 2011 5:24 pm**

Hello,

If you look at the contents of the DS1820 functions using the custom code feature then you can see that the functions are simply referencing the generic 1-wire function calls. You should be able to copy the function calls and syntax directly into Flowcode if you wish using component macros etc.

Here is the DS1820_start_conversion function as an example.

Code: Select all

	char in = 0;
	char counter = 0;
	oo_busreset();
	oo_tx_byte(OO_SKIPROM);		// Command all temp sensors on the bus to start a conversion
	oo_tx_byte(OO_CONVERTT);	// Convert temperature
	while (in == 0)
	{
		in = oo_rx_byte();
		delay_ms(4);
		counter++;
		if (counter == 0xFF)		// Security: if the conversion is not completed
			return 1;				// after > 1 sec -> break.
	}
	return 0;

Defines such as OO_SKIPROM can be found in the defines section in the custom code window.

Matrix user forums

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