1wire developments ?

FORD

Hi all,
Now that Jon has sadly left the group, is there any further development with 1wire stuff on propeller·?
Jon was working on something a while ago.

Cheers,
Chris

Javalin

Hi,

I was thinking about doing an object - I've recently done the i2c and an SPI object

But when I looked arround there was not many chips for 1-wire - and of those I can get all the functions on an i2c equivalent chip.

James

Gadgetman

Ah, but the big difference is that you can use so many more of the 1-wire chips.

Imagine wiring a whole building with temperature sensors, then adding DS2406 switches to it, to switch lights and heating, using iButtons on the doorlocks...
and ALL of them connected to the same pin on the Propeller.
After all, you're NOT limited to the 2 or 3 address lines on a I2C chip, but only by the 8Byte serialnumber of the 1-wire chips...

I have a couple of VERY nice iButtons, known as ThermoChrons...
These contains a timebase, a bit of memory and a temperature sensor.
you start the clock on it, set an initial delay and a repeat delay, then forget it.
Then it will wait for the prescribed amount of time before taking and storing a temperature measurement, go back to sleep for a while and wake up again to take the next measurement and so on and on and on...

Stick one such on a crate, then have a reader where they load and unload crates. Not only can you immediately identify the crate(unique serialnumer), but you can also tell whether or not the cargo has been transported at the correct temperature.

There are digital pots available. I assume such also exist for I2C, but how many can you control using I2C?
Without using up all available pins, that is?

And they have another trick up their sleeves...
The 'Skip ROM' command system. With this you can address ALL chips of the same type at once. Imagine setting the timebase of 100 Thermochrons at the same time, or telling every thermometer on the third floor to take a measurement at the same time?
(And you can know almost instantly if one of those thermometers found a temperature outside the accepter range.)

You see, I2C is a data BUS, but 1-wire is a NETWORK architecture...

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Javalin

I stand corrected.

BTW - each i2c bus can support 127 devices - without going into clever bus-expansion techniques. Each device has a base address which is offset by the address lines on the chip, so for EEPROM for example you could get 8 of the same type of chips on the same bus.

James

Oliver H. Bailey

Hello Everyone,
My book Embedded Systems Desktop Communications goes very heavy into the 1-Wire interface. I hve circuits in there that can get over 1,000 feet ona 1-Wire network leg. There are several chips out there from Maxim/Dallas that provide USB, Ethernet, and RS232/RS422 1-Wire interfaces. While I2C will work, you can't get the distance to go through an entire building. The 1-Wire Pot is also a very nice piece of work.

Regards,
Oliver

FORD

Does anyone at Parallax have an answer to my 1wire development question ?

Cheers, Chris

Chris Savage

Chris,

·· We're currently focusing on getting the remainder of the documentation completed and will continue to release useful objects, but the nice thing about the Propeller is that so many people are already releasing nice Objects and perhaps if a few with the experience on 1-wire protocol got together they could really come up with a nice object.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

FORD

Thanks Chris,

Gadgetman

If worst comes to show, we could always stick a DS2480b in there and use one of the serial objects...

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FORD

Hi Gadgetman, and thanks for the suggestion.

You are correct, and its probably a nice simple way around it for the moment.

I've·used the ds2480B when using a bs2sx. Now we use bs2p and do 1wire straight from the i/o pin. The code is much more complicated using a ds2480B compared to the owin and owout commands with a bs2p. There are also a few hidden command byte traps with the ds2480b, but it is still a nice chip to use if you cant use a bs2p.

Jon was working on something 1wire for the propeller a while ago, and I had word earlier on that there·may possibly be some Parallax objects produced fairly soon after the propeller release.

I guess I should just give the guys some time, I couldnt do it in ASM myself anyway, I dont have time to attempt that unfortunately.

Thanks again for the suggestion,

Cheers,
Chris, Western Australia (where its a freezing 14 degrees at the moment, well, thats cold for us!!, we have the heaters on.)

Gadgetman

I'm looking to do a bit of 1-Wire myself, but only a small bit of code.

I need to be able to do a 1-Wire reset and detect the presence pulse(if any) in assembly, and at the lowest speed possible.
It's part of the design for my car-computer.
It'l be doing this check every second or two, in as low-power setting as possible so as not to drain the battery. (I'm going to use an iButton for unlocking the car, and if I leave it for a week or two in the winter, I would like to still have enough juice in the battery to start the car...)

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parsko

I too, will be interested to have 1-wire capability. Gadgetman, I will also be doing the same exact thing, but for my motorcycle (where security is much more difficult to maintain).

Is anyone aware of how far the existing 1-wire development has come? I ask because it might be possible for someone else to "finish the job" (not me, I'm still barely able to make an LED blink... without the blinkLED.spin object)

-Parsko

camt

Hi all,

1-wire support routines have been submitted to the object exchange and included in new posting.

Cam

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Cam Thompson
Micromega Corporation