aag and 1wire interface issues...good instrument but weird setups

[ksdehoff]

Hey again:

So I have been able isolate the problem reading my aag wind instrument to an interface issue of some sort. I am able to make the wind instrument work via a 9490 usb interface on two computers, but only if it goes through an unpowered USB 2.0 hub. Plugging the interface directly in to either computer causes the odd data reports (ie 0,0,2.5,0). With the interface connected via this cheap usb hub though it works great.

So plugging the 9490 directly in to my computer gives the same results as the 6 channel serial hub, which is what I would clearly prefer to use, since I have more than 1 1wire segment. Also remember that in all of these scenarios, everything except the wind direction works fine.

I'm hoping there's enough information for an A-HA that I'm doing something obviously simple and wrong! In all my testing I only have the wind instrument connected to the interface via that rj12 cord that came with it, and the 1/4 rj12 jumper is installed.

There must be a logical explanation!
Thanks
Ken

 

[ericvic]

Ken,

That is very strange and I don't see why where the USB adapter is plugged in would make any difference to the readings from the DS2450. The only thing I can think of is the voltage on the DQ line. Can you measure the voltage of the DQ line when the USB adapter is plugged into the hub and when it is plugged directly into the computer?

Eric

 

[ksdehoff]

Eric:

The information for my 3 configurations:

Serial Hub: 5.10 volts - does not work
USB Direct: 5.04 volts - does not work
USB/Hub: 4.42 volts - works fine

Bizarre
Thanks for giving this some thought.
Ken

Ken,

That is very strange and I don't see why where the USB adapter is plugged in would make any difference to the readings from the DS2450. The only thing I can think of is the voltage on the DQ line. Can you measure the voltage of the DQ line when the USB adapter is plugged into the hub and when it is plugged directly into the computer?

Eric

 

[ksdehoff]

All:

I believe I've eliminated all variable components except the instrument itself and the maxim driver through a lot of component swapping. Are there any 1wire diagnostic tools like a sniffer that are available to help see more clearly exactly what's occurring on the wire?

Ken

 

[ericvic]

Ken,

I think there are some 1-Wire sniffers out there but they are pretty expensive. An oscilloscope works well for viewing the waveform but you would need to dig into the protocol to decipher what is going on.

Eric

 

[ksdehoff]

Eric:

No thanks! That's way beyond me.

I've been tinkering some more and have gotten closer - I can manually configure the 2450 on the serial port to work correctly, so the problem appears to be one of not getting the initialization done correctly. Do you have any experience on why initialization may occur in some configurations (ie usb with a hub) and not others (serial).

Thanks for your help
Ken

Ken,

I think there are some 1-Wire sniffers out there but they are pretty expensive. An oscilloscope works well for viewing the waveform but you would need to dig into the protocol to decipher what is going on.

Eric

 

[ericvic]

I don't have any idea why the initialization of the DS2450 would occur differently with the different 1-Wire masters.

Eric

 

[ksdehoff]

Eric:

A couple of questions for you. On the adapter weirdness, I've created a reliable lab on the 9490 via usb hub. With the hub self powered the adapter works. As soon as I power the usb hub with a transformer, the adapter stops reading the wind direction correctly. Unplugging the hub going back to self powered gets the wind direction working correctly again. Very consistent result after trying 20 times (plug/unplug). If there is only data and ground coming off the 9490, what could be causing this???

My second question is that when I have temp/solar/humidity connected to the wind meter, the voltages of the wind direction read .5 volt low - could this be caused by inadequate power for parasitic operation and would changing poll frequency or some other parameter help to improve this?

THanks
Ken

I don't have any idea why the initialization of the DS2450 would occur differently with the different 1-Wire masters.

Eric