I am thinking of using Semtech LR1110 for designing tracking device in field with LoRa. Since this one has GNSS & LoRa on SoC, so going with LR1110.
But I have a concerns about LR1110.
How can I use GNSS data to get accurate GPS location ?
Is there any open source (free) way to get GPS coordinates from GNSS data ?
Will I be able to connect device based on LR1110 to LoRa gateway ?
We do not know yet the API for the GNSS part so it is not really possible to answer. But it would be surprising if it is complex to get the actual location considering this is exactly the goal of the chip.
As for the connection to a LoRa gateway, you won’t have any issue, the LoRa part is completely inter-operable with all the others LoRa chips.
For those interested in this device, from the contents of The Things Virtual Conference on April 16
Semtech - Deep dive into the new LR1110 chip
LoRa, WiFi and GNSS on a single chip. Experts will take a deep dive into the LR1110.
You would think so, GNSS is a term that describes the various ‘Global Navigation Satellite Systems’ in orbit such as GPS, GLONASS, Galileo, Beidou etc.
There are devices such as Mediateks that only receive the GPS satellites, but Ublox devices can receive GLONASS, Galileo, Beidou etc, so its more accurate to describe them as GNSS devices.
According to datasheet, the LR1110 cannot do the location calculation itself. It depends on back-end server:
The LR1110’s GNSS Geolocation System achieves low energy geolocation by offloading time- and compute-intensive operations to back-end system components.
The LR1110 features a fast and low-power GNSS scanner. The device captures a short portion of the signal broadcast by the GNSS satellites, and extracts the information required to calculate the device position - the pseudoranges. This information is aggregated into a NAV message which can be sent to a back-end system to compute the device position.
A low power GPS, does the location calculation very quickly, I would suggest the amount of power it uses to do the actual calculation is very low.
Sending the data somewhere else to do the calculation via LoRa you would think takes more power not less.
I can see that it might be useful in some applications to have the ‘pseudoranges’ on a central server somewhere, but the device not having the capability to do its own location calculation, like a standard GPS, seems to be a bit odd.
Unless you use Kolmostar’s magical jedi-200 module: https://www.kolmostar.com/products-low-power-jedi-200
Which, amazingly, claims to be able to send the ephemeris data in 50 bytes only every 12 hours! Needless to say I have not been able to get my hands on a module. I wonder if their algorithm has been licensed elsewhere.
I spoke with Semtech recently and was told you would have to implement your own GPS solver on a connected microcontroller if you wanted to operate in this way, since the LR1110 offloads this processing to reduce power consumption.
To the second question, yes, the LR1110 includes everything you need for multi-region LoRaWAN communication.
If you’re interested in testing it I’m going to be putting together some modules as soon as the part is available for sampling! I also wrote up a few posts that explain just how the device operates in terms of positioning.
There is a very technical video from Nicolas Sornin about th LR1110, for The things Network virtual conference: he addressed the question on why the chip is limited to pseudo-range (mainly the chip would need a lot more up-to-date information to be able to do the processing) : https://youtu.be/AQ1tSzmhDrg
He talks about the GNSS part around 25min, but the whole video is very interesting
Did anyone ever try to implement their own GPS solver on a connected microcontroller? I’m wondering what the footprint of the solver is and if maybe a Cortex M4 is able to accomplish this job.