GPS in motion or stationary

[crumble]

@Martinnn

The L-76 GPS has a lot of power saving options. It uses an internal memory to store the almanac. The chip itself can track your route for some time. The the normal documentation does not mention the format of this data. I guess you have to pay an additional fee to use this feature.

[PeterB]

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[PeterB]

@crumble said in GPS in motion or stationary:

@Martinnn

The L-76 GPS has a lot of power saving options. It uses an internal memory to store the almanac. The chip itself can track your route for some time. The the normal documentation does not mention the format of this data. I guess you have to pay an additional fee to use this feature.

I would indeed expect i stores the almanac data when 'switched off'. Major question is wether it is switched off nicely in the correct power save mode by pysense. The pysense is not designed to take sleepmodes seriously (e.g. ESP32 RTC disabling and OS killing instead of shutdown).

[jcaron]

@PeterB from what I understand it’s not permanent storage, the L76 needs to stay powered to keep the data, however it can get to a pretty low power mode and still keep that data. You’ll have to tell the chip to move to that mode.

The Pytrack can be set to sleep while still powering the GPS chip.

[crumble]

@PeterB said in GPS in motion or stationary:

I would indeed expect i stores the almanac data when 'switched off'.

go_to_sleep has an option to power the GPS

Major question is wether it is switched off nicely in the correct power save mode by pysense.

No, you have to send the right MTK sentences to the L76. MTK sentences are used to configure the chip. There are 4 ways to start it. If you want to use the most energy and time saving mode, you have to take care about a lot of stuff. You have to ensure that the alamnac is stored in the GPS and last fix is not older than 3 hours.

Therefore you cannot use the PIC deepsleep or you need an external RTC.

It shall work. I gave up because of i2c and own errors. I can try it again this week and share my result.

[Martinnn]

@crumble Just to re-confirm, the only way to get the almanac on the GPy is to download it from the GPS network itself, which takes 12.5 minutes (due to the low baud rate) after a cold start:
https://stackoverflow.com/questions/16384844/is-there-a-way-to-download-the-gps-almanac
I was looking for an "assisted" version that lets you download the data, but for this GPS chip this does not seem to exist.

[jcaron]

@crumble said in GPS in motion or stationary:

Therefore you cannot use the PIC deepsleep or you need an external RTC.

That seems incorrect. You can set the PIC to deep sleep while keeping the GPS powered. You would have to set the GPS chip to backup mode before going to sleep (and wake it up after sleep), though.

[crumble]

@jcaron said in GPS in motion or stationary:

@crumble said in GPS in motion or stationary:

Therefore you cannot use the PIC deepsleep or you need an external RTC.

That seems incorrect. You can set the PIC to deep sleep while keeping the GPS powered. You would have to set the GPS chip to backup mode before going to sleep (and wake it up after sleep), though.

You need to know that the L76 is not sleeping longer than 3 hours, if you want to use hot start. If you can calculate the deepsleep time from the PIC its incorrect. I have always the primitive timers of my short AVR experience in mind.

[crumble]

@Martinnn said in GPS in motion or stationary:

I was looking for an "assisted" version that lets you download the data, but for this GPS chip this does not seem to exist.

The documentation mention an AGPS mode called EASY and how to set and query the mode. By default it is on. But it neither tells how to upload data nor which format is needed.