solutions
LoRa Basics Modem and LoRa Edge documentation
Scenario - GNSS Assisted Scan¶
Introduction¶
One of the key features of the LoRa Edge™ Platform is the ability to scan GNSS signals and provide the measurements to the LoRa Cloud™ Modem & Geolocation Services to determine the location of an end device. In this chapter, we review the requirements for completing an assisted GNSS scan with the LR111x device and for returning that data to the MCU.
GNSS assistance provides information that limits the number of variables the GNSS scanning algorithm must take into account in its search for signals. This helps to shorten the amount of time that a GNSS scan takes. By providing the approximate time (within 30 seconds), the assistance position (within 150km), and the GNSS almanac, the algorithm can estimate which satellites are in view, along with their Doppler at the time of the scan. The assistance data also provides information on the frequency offsets of the GNSS signals, which limits the search time for the signals from the visible satellites.
Prerequisites/Dependencies¶
Common:
Must have synchronized the LR111x clock with the Clock Sync process (or some other source) to within 120 seconds (ideally within 10 seconds)
Must have an almanac less than 15 weeks old (ideally is less than 4 weeks)
Must have an aiding position from the application server or another source better than 150km (ideally within 50km)
Must have an SPI connection to exchange information between the device application and the LR111x chip
For GNSS operation, must have a temperature-compensated crystal oscillator (TCXO) accurate to within 5ppm
Prerequisites for LoRa Basics™ Modem:
Not applicable
Prerequisites for LoRa Basics™ Modem-E:
No additional requirements
Prerequisites for a Transceiver:
If using a LoRaWAN® network to perform Clock Sync, almanac, or position assistance, the MCU must have a LoRaWAN stack.
Step-by-Step Procedure¶
LoRa Basics Modem-E¶
Complete the Clock Sync/time transfer, almanac, and assistance position steps noted above.
Note
If Clock Sync, the almanac, or the assistance position require a network server or LoRa Cloud Services, joining the network is also required.
Optionally, specify the constellations to scan. (By default both GPS & Beidou are scanned.)
Through the SPI interface, the host MCU calls the GNSS assisted scan command (
0x0431
) of the LoRa Basics Modem-E.Note
Scan options include: Effort Mode, ResultMask, and NbSvMax.
Depending on the effort level, scans may take 2-10 seconds per constellation.
A
NbSvMax
value greater than 10 results in power consumption with little to no benefit for LR111x. AnNbSvMax
of 10 or less is recommended to save power on both the data collection and transmission of the scan results.
When the scan is complete, the EVENT signal on the LoRa Basics Modem-E is set high.
The device application calls
GetEventsize
(command0x0633
) andGetEvent
(command0x0600
).The LoRa Basics Modem-E returns the assisted GNSS scan results.
The LoRa Basics Modem-E sets the EVENT signal low.
Transceiver¶
Complete the Clock Sync/time transfer, almanac, and assistance position steps noted above.
Note
If Clock Sync, the almanac, or the assistance position require a network server or LoRa Cloud Services, joining the network is also required.
Optionally, specify the constellations to scan. (By default both GPS & Beidou are scanned.)
Through the SPI interface, the host MCU calls the GNSS assisted scan command (
0x040A
) of the LR111x.Note
Scan options include: Effort Mode, ResultMask, and NbSvMax.
Depending on the effort level, scans may take 2-10 seconds per constellation.
A
NbSvMax
value greater than 10 results in power consumption with little to no benefit for LR111x. AnNbSvMax
of 10 or less is recommended to save power on both the data collection and transmission of the scan results.
During the scan, the BUSY signal is high.
When the scan is complete, the IRQ signal (if enabled with
GNSSDone
) on the LR111x is set high and the BUSY signal is set low.The device application calls
GnssGetResultSize
(command0x040C
) andGnssReadResults
(command0x040D
).The LR111x chip returns the assisted GNSS scan results.
If enabled, the LR111x chip sets the IRQ signal low.
Used By¶
Device application, LR111x chip, LoRaWAN network server, LoRa Cloud Join Server
Troubleshooting¶
If the GNSS Event starts with 0x00
the payload is NOT to be sent to the application server for processing. This GNSS event message is called GNSS Events for the Host MCU in the Reference Manual and does not contain a NAV message. Check the second byte and refer to the LR111x user manual for its significance.
LoRa Basics Modem and LoRa Edge documentation
Table of Contents
- Overview - LoRa Edge™ Asset Management Platform
- Use Case - Basic Asset Tracking
- Use Case - IR Image Upload on Detected Motion
- Scenario - GNSS Assisted Scan
- Scenario - GNSS Autonomous Scan
- Scenario - LoRa Basics™ Wi-Fi Passive Scan
- Scenario - GNSS Scan with ROSE
- Scenario - Wi-Fi Scan with ROSE
- Scenario - LoRa Cloud™ Join Server
- Scenario - Claiming a Device
- Scenario - Unclaiming a Device
- Scenario - Modem-E Initialization
- Scenario - LoRa Basics™ Almanac Update
- Scenario - User Loaded Almanac Update
- Scenario - Intermittent Network
- Component - Clock Synchronization
- Component - Large File Upload
- Component - Reliable Octet Stream Encoding
- Cryptographic Engine
- Glossary
ADDITIONAL RESOURCES - VIDEOS