Trickle Mode

lills · Occasional Visitor Joined: Mar 04, 2004 Posts: 18

Hi,

I have read a few articles that discuss trickle mode. From what I gather it extends the battery life of the gps device by going into stand by mode and sending signals on intermittently instead of constantly.

I have a Navman 4400 bluetooth GPS together with an IPAQ 5450. I use both the Tomtom Navigator and Memory Map software. I was wondering if anyone could explain trickle mode in more detail and also explain how to enable it with my setup.

Many thanks,

Lills

lbendlin · Posted: Tue Mar 09, 2004 1:49 am Post subject:

Normally the GPS receiver is permanently powered, but it produces position updates only every second.

So most of the time it is twiddeling thumbs. Trickle mode tells it to report the position, then go to sleep for a while (until the next full second), then wake up and report the next position.

While you can specify any value for trickle mode it is advisable to give the receiver at least 200 milliseconds to find the position and report it to the client device. If you reduce the wake phase more (let's say 100 ms) it may not succeed in getting a position, and you will have dropouts from the normal once-a-second cycle.

200 ms versus 1 second already expands the battery lifetime five-fold. Well, theoretically. But you can see a nice increase somewhere in the two-fold range.

I am not sure how you set that up on the Navman, but for the Emtac based devices you can use the Crux_View program to enable trickle mode.

NOTE: Manufacturers strictly discourage trickle mode. Why? Because they are chicken... No, seriously, it does have its complications, and they don't want to handle the support calls.
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Lutz

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lills · Occasional Visitor Joined: Mar 04, 2004 Posts: 18

Thanks for the info Lutz

Taking the Emtac based device as an example in what way does Crux_View write this information to the gps? Does it modify the firmware/driver on the pda or the gps device itself?

Many thanks

lbendlin · Posted: Tue Mar 09, 2004 3:39 am Post subject:

it modifies the firmware on the gps device directly. Nothing changes on the Pocket PC
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Lutz

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lills · Occasional Visitor Joined: Mar 04, 2004 Posts: 18

Does this mean that the lower the setting (in ms) the longer the battery will last.

If I were able to set my Navman to a safe time of 300ms, say, would I notice a any difference in the way it performs. Could you tell me what the possible disadvantages are?

Many thanks

lbendlin · Posted: Tue Mar 09, 2004 3:05 pm Post subject:

yes, it yields a longer battery performance. Negative side effects may be dropped update cycles in sub-optimal reception situations. Not important when walking (that's basically what trickle mode is for).
_________________
Lutz

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lills · Occasional Visitor Joined: Mar 04, 2004 Posts: 18

Lutx,

You are a font of knowledge.

I managed to get Crux_View to work perfectly with the Navman. I have managed to get it to communicate at baud rates ranging from 4800 through to 57600. Are there any advantages with using high baud rate, or should I stick to 38400?

Secondly, What is the difference between using NMEA and Sirf protocols and which do you prefer?

Many thanks

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