LoRa Basics Modem and LoRa Edge documentation

Scenario - GNSS Autonomous Scan

Introduction

One of the key features of the LoRa Edge™ system is the ability to scan GNSS signals and provide the measurements to a LoRa Cloud™ processing system to determine the location of a device. Here, we review the requirements for completing an autonomous GNSS scan by the LR111x chip and for returning it to the device application.

Compatibility

LoRa Basics Modem(s)

LoRa Edge LR1110 transceiver

Prerequisites/Dependencies

Common:

  • Must have an SPI connection in order to exchange information between the end-device application and the LR111x chip.

Prerequisites for LoRa Basics™ Modem:

  • Not applicable

Prerequisites for LoRa Basics Modem-E:

  • No additional requirements

Prerequisites for a Transceiver:

  • No additional requirements

Step-by-Step Procedure

LoRa Basics Modem-E

  1. Optionally, specify the constellations to scan. (By default both GPS & Beidou are scanned.)

  2. Through the SPI interface, the host MCU calls the GNSS autonomous scan command (0x0430).

    Note

    • Scan options include: Effort Mode, ResultMask, and NbSvMax.

    • Depending on the effort level, scans may take 2-10 seconds per constellation.

  3. When the scan is complete, the EVENT signal on the Lora Basics Modem-E is set high.

  4. The host MCU calls GetEventsize (command 0x0633) and GetEvent (command 0x0600).

  5. The LoRa Basics Modem-E returns the assisted GNSS scan results.

  6. The LoRa Basics Modem-E sets the EVENT signal low.

@startuml autonomous_gnss_scanbox "End-Device" #ADD8E6    participant "Application" as APP #ADD8E6    participant "LoRa Basics™\nModem-E" as LR1110 #00ADEFend boxlegend left|=             |= Owner || <#00ADEF>    | Semtech || <#ADD8E6>    | Customer || <#D3D3D3>    | Ecosystem |endlegend== Optional-Set GNSS Constellations to scan ==note over LR1110, APP #AAAAAA: Set GNSS Constellations (default: GPS+Beidou)APP -> LR1110 : GNSS Set Constellation to use (Cmd 0x0400)note right: Requires bitmask that documented in the \nLR1110 User Manual (bit 0=GPS, bit 1=Beidou)LR1110 -> APP : Setting confirmed== Autonomous GNSS Scan == APP -> LR1110 : GNSS Autonomous scan (Cmd 0x0430)LR1110 -> APP : Event high note right: Event\: GNSS scan doneAPP -> LR1110 : GetEventsize (Cmd 0x0633), GetEvent (Cmd 0x0600)LR1110 -> APP : GNSS scan done + Resultsnote right: Scan results ready for trasmission or local storageLR1110 -> APP : Event low        @enduml

Note

After a successful scan when a precise timestamp is not available, it is important that the data is transmitted to the application server for processing as soon as possible, with the associated capture time of t=0.

Transceiver

  1. Optionally, specify the constellations to scan. (By default both GPS & Beidou are scanned.)

  2. Through the SPI interface, the device application calls the GNSSAutonomousScan command (0x0409).

    Note

    • Scan options include: Effort Mode, ResultMask, and NbSvMax.

    • Depending on the effort level, scans may take 2-10 seconds per constellation.

  3. If GNSSDone is enabled, the IRQ signal on the LR111x chip is set high.

  4. The device application calls GnssGetResultSize (command 0x040C) and GnssReadResults (command 0x040D).

  5. The LR111x chip sets the BUSY signal low .

  6. The LR111x chip returns the assisted GNSS scan results.

  7. If enabled, the LR111x chip sets the IRQ signal low.

@startuml autonoumous_gnss_scan_trxbox "End-Device" #ADD8E6    participant "Application" as APP #ADD8E6    participant "LoRaWAN® Stack"  as LWS #ADD8E6    participant "LR111x\nTransceiver" as LR1110 #00ADEFend boxlegend left|=             |= Owner || <#00ADEF>    | Semtech || <#ADD8E6>    | Customer || <#D3D3D3>    | Ecosystem |endlegend== Optional-Set GNSS Constellations to scan ==note over LR1110, APP #AAAAAA: Set GNSS Constellations (default: GPS+Beidou)APP -> LR1110 : GNSS Set Constellation to use (Cmd 0x0400)note right: Requires bitmask that documented in the \nLR1110 User Manual (bit 0=GPS, bit 1=Beidou)LR1110 -> APP : Setting confirmed== Autonomous GNSS Scan == APP -> LR1110 : GNSS Autonomous scan (Cmd 0x0409)LR1110 -> APP : BUSY signal high note right: IRQ signal high (if enabled)\: GNSS scan doneAPP -> LR1110 : GnssGetResultSize (Cmd 0x040C), GnssReadResults (Cmd 0x040D)LR1110 -> APP : GNSS scan done + Resultsnote right: Scan results ready for trasmission or local storageLR1110 -> APP : IRQ Signal low (if enabled)@enduml

Note

After a successful scan when a precise timestamp is not available, it is important that the data is transmitted to the application server for processing as soon as possible, with the associated capture time of t=0.

Used By

Device application, LR111x chip

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.

References