_Art_
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Posts posted by _Art_
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I’d say it’s the fastest the chips can do so that it can do it’s business quickly and go back to sleep. Maybe about a 10MHz SPI clock.
I see activity on my scope, but it has issues with waveforms at that speed. I’ve also got LEDs on both data channels, and they make things more obvious.
I totally forgot this thing has the transmit half of a serial port. It does output data, so I might as well go for the easy part first.
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The 64st only takes a few seconds from turning chirp search on, to find the chirp, then another 6 or so seconds to read in it’s info.
Most modern microcontrollers have low power sleep modes that are set to wake on desired events such as interrupts, or expiry of a timer.
In this case both chips have. The transceiver probably wakes up when it’s selected with it’s enable pin.
If only my scope had SPI decoding, I’d see the packets now, but unfortunately it will take me some more building and programming to get another microcontroller to do it.
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So far that there’s a quick burst of activity on the bus every 2 seconds whether a device is searching for it or not.
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As far as I’m aware, nobody has looked at it, so anything I find out is new.
Here’s the still working chirp with exposed SPI interface. This also has a temporary PCB to test what is done so far.
It lowers the voltage of one of the SPI data channels, and then mixes them both together with diodes so both data channels can be seen on one channel of a scope.
One channel will be of lower amplitude than the other, so easily distinguishable which channel is which (which direction data is flowing),
but both SPI data channels only using a single scope channel.
When I’m done with that, my own microcontroller (dsPic) daughterboard will go there.
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Still works!
All good from here I think. The third wire has a PCB via I can scrape the coating off, and use.
The fourth wire is for the last pin on the side of the chip, so I can lead the wire in sideways.
I’ll probably need a blob of potting compound to drop over it when done... before something breaks.
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Ok, I’ve mounted it, and externally powered it without breaking it so far
The only hairy part is coming up. Breaking out the SPI interface between the microcontroller and transceiver chip to read it.
Wish me luck!
I got two of them in case of ruining one, but I’d rather keep the second chirp intact.
I swear they called the whole thing Ant because of the two antenna pins.
.... and... four connections can’t be made across one side of the chip because the insulation won’t fit!
I’ll have to stagger connections between both chips on the SPI bus. I didn’t foresee that one!
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I’ve loaded more than 32GB of Birdseye imagery from Basecamp to the 66, and even when the imagery is already downloaded,
it still takes a very long time to copy to the device. I never had any issue like that.
I always plug the device in before turning it on. Not saying that makes any difference, but it is what I’ve done.
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I wonder what sort of current it takes to permanently damage the battery pack.
It’s a slow charge, but funny pondering the possibility that everyone leaves units on charge face down, so battery gunk leaks through the card slot, and ruins the PCBs.
It’s not a problem that particularly bothers me. At least it doesn’t interfere with the device working,
but I’d have thought it something the manufacturer should be concerned about.
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Garmin (via Facebook) told me to contact support for an engineering ticket about other bugs, but I don’t think it’s worth the time.
Especially where others have the same problem. They would probably just tell you to do a master reset, which I’ve already done,
and maybe in the end, exchange the unit, but they might as well just swap units around amongst the people that returned them
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Same thing here after at least 16 hours (possibly up to 17).
It looks like the battery is fully charged, but the charging graphic keeps animating here as well.
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Thanks for the replies
Atlas, do you have a rough figure for current draw with backlight off in usual operation?
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I’m pretty sure mine did stop charging, but I’ve put it on again now to be sure.
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Hi
I’ve just some questions about Garmin Chirp beacon...
1) Does anyone know what the penalty is with regard to battery life for the GPS device if Chirp searching is left on full time?
2) Do geocache databases supplied to GPS units have some flag to indicate they have a Chirp with them so the user knows to activate searching?
3) For anyone who has actually placed one... Did you get the whole year out of the supplied battery?
Cheers
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On 12/22/2018 at 6:16 AM, barefootjeff said:
Did you actually look at this link? It's still a form of differential GPS ..
Obviously not!
On 12/22/2018 at 4:23 AM, Thistler said:A TCXO module can use as little as 2 mA. Of course, what you are describing is essentially a TCXO in software instead of dedicated circuitry.
Kind of, but a resistor would be turned on to heat the crystal oven to make the freq stable, rather than adjust a DDS to compensate.
UBlox have a page about oscillators, and the same manufacturer produces GPS modules with TXXO and without.
I guess the handhelds do have them, or they wouldn’t be able to even maintain the appearance of keeping up.
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7 hours ago, lucia152 said:
This part of _Art_'s post had me thinking. When I experienced the screen freezing (at least twice), it was while I was a passenger in a moving car. While I don't normally use my handheld for highway navigating, I do zoom in and out of the map, back and forth between different screens (cache descriptions, POIs), planning stops for further down the road. I'm now wondering if the GPSMap 66 is somehow struggling when under more rapid fire conditions than when on foot. Opinions?
The easiest way I can get it to turn itself off without entering a known sequence of buttons that will do so, is to zoom out far and make it draw a big detailed map screen.
If it can manage that, then moving around the map at that level with the pointer will surely crash it before long.
Then when it’s turned back on, it’s going to try to draw the same map display as before, and simply turn straight back off again.
What I think was happening is I took it in the car after one of these shutdowns. It would have to either get a position fix, or at least be trying to rotate to a different bearing
before trying to draw it’s first map screen so that it was doing something different.
I have little doubt that if I’d turned it on and got it displaying a map first (at a closer level) it would have been fine.
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I’m not lying when I say I don’t trust it enough to use it
But I’m going by their own user manual in "Satellite Settings”, and also people on GPS forums claim to have tested the difference.
So all that’s left is if one of the GPS module updates that have been released has improved the power performance for multiple service support.
I doubt it
No identical sets of batteries here to test. Are you into wasting four new batteries to find out? I might be if they were already here.
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Did I say sub meter accuracy? No, Let’s make that down to millimetres margin of error with relatively cheap hardware.
This is not some glimpse into the future. You can buy a stock mass market GPS module with centimetre level accuracy right now,
and it’s actually old news: https://www.u-blox.com/en/high-precision-positioning
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I agree entirely, except that the GPS is featured in a way with alerts so that your phone could stay in your backpack unless you actually have to make a call.
But in the end, I wouldn’t care at all if all connected features were simply deleted tomorrow in exchange for a more reliable update regarding the real function of a mapping GPS
I’m trying to at least give them props for something. It’s hot here now, so there’s no clouds, or anything to show on the radar,
but they are nice computer generated clouds for cloud cover, and it’s good that you don’t have to tell it where you are.
When it’s fixed not to break something else, I’d have to admit it’s a nice job, even if just from a demo point of view.
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On 12/14/2018 at 10:45 AM, Thistler said:
The accuracy of a quartz oscillator can be far better than +- 20ppm. Inexpensive temperature compensated quartz crystal modules can be accurate to around +- 2 ppm when exposed to the typical ranges of temperature one would experience outdoors, and these consumer very little additional energy than a simple quartz crystal. To get even better accuracy from a quartz oscillator you can use a oven-ized quartz oscillator module, but these are larger and far more energy intensive.
A TCXO would be a power guzzler in a handheld. They shouldn’t be needed because the temperature coefficient of the crystal is known.
You only need to monitor the temperature inside the unit (which Garmin handhelds do), and you can offset the drift fairly accurately.
On 12/13/2018 at 8:21 AM, Cheminer Will said:I see, so you think with a newer unit like the 66 series, there would be no reason to set it to GPS only, but just keep it on GPS + Glonass?
If power consumption is of no concern.
On 11/12/2018 at 7:33 AM, barefootjeff said:Differential GPS can (according to Wikipedia) provide accuracies of up to 10cm, but it requires a close-by base station at a known location to cancel out some of the errors and distortions in the raw GPS data.
Not at all. New technology exists for fairly ordinary hardware to independently obtain accuracy down to sub meter accuracy with carrier phase recievers.
By the time the error was turned off in the early days so that civilians could access today’s kind of accuracy, it was already moot.
Farmers worked out that the error was uniform across all civilian units, so they only needed to put a GPS in a known location,
and send the offset for the true location to a second receiver (the unit that is actually moving), and then add the offset from the stationery unit to the reported coordinates
of the second unit, and then you have overcome any deliberate error that the Government introduced, and are only left to suffer inherent error from both GPS receivers.
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I had a play with the Weather app thingy over wifi that I was rather impressed with.
Though I’m not fussed about connected features, it is very tidy... or at least until I tried to make these screenshots to show others:
To capture these, of course I don’t want to show the world my location, so I turned GPS off, and set an arbitrary position for simulation from the Satellite screen.
Then capturing the screens in a fake location was fine, but then when setting a different position on a map again from the Satellite screen,
the entire weather app context is displayed again! From there, you can’t browse the map again for at least the entire power cycle.
Not a big deal for this scenario, but I’ll bet there’s other areas a map view will be needed when the Weather app will essentially be displayed instead.
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Never as far as I know. I was only suggesting a possible way you could bypass the shutdown or freeze you have by not making the quit button return to the map screen.
ie. begin making or finding waypoints, etc. from some screen other than the map screen, and then when you exit the menu, it won’t try to exit to map screen.
EDIT,, Actually it’s Cheminer Will I’m talking about here... I think it could prevent his unit turning off in the situation he’s describing.
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That’s basically what I mean, yes.
I’d expect FIND and MARK buttons to do the same thing no matter where you are in the GUI,
and for every GPSMAP model as far back as those buttons exist,
but I only tested from the Compass screen, and they do as they are supposed to on the 66 from there.
Not sure that it will solve the problem you have with it, but it does for another issue I already talked about earlier in the thread.
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Because the words Find and Mark mean Find and Mark respectively. They are dedicated buttons.
I just tested them both from the Compass page, and they both do the same as if they were pressed in the map screen.
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For now, I suspect those won’t be an issue if you start from a screen other than the map display,
in which case, the find and mark buttons should have the same function.
Chirp Qs
in GPS technology and devices
Posted · Edited by _Art_
I don’t expect much from it other than seeing valid data. I expect that to be encrypted though. Garmin wouldn’t want clones to be easily made.
Since the GPSr sends the timestamp and serial number, I’d be using both of those to encrypt the rest of the transaction if it were me making it.
It’s possible the timestamp and serial number will be in the clear, but they could also have some obfuscation known by the GPSr and Ant device.
The serial was boring. While the Chirp is idle, it outputs “0xE0, 0x00” bytes every two seconds at 4800 baud 8N1.
While transmitting to a GPSr, there’s a few more byte values in there, but none of it has any meaning in ASCII.