LoRa Basics Modem and LoRa Edge documentation

Scenario - User Loaded Almanac Update

Introduction

The LR1110 can reduce the GNSS scanning time by taking into account coarse orbital parameters for different GNSS constellations (the almanac parameters). In conjunction with a coarse time and position estimate, the LR1110 uses this information to optimize the search for, and acquisition of, GNSS signals. Over time, the true satellite positions diverge from the stored almanac parameters. This means that those parameters need to be updated regularly.

This can be done by the application with a full almanac update, where the device application updates all almanac data in the LR1110.

Note

If the LR111x is used as a LoRa Basics Modem-E, energy and bandwidth-efficient OTA updates can be used. For more information, see the LoRa Basics Almanac Update scenario.

Compatibility

LoRa Basics Modem(s)

LoRa Edge LR1110 transceiver

Prerequisites

Common:

  • The application can download the almanac image from das.loracloud.com and provide it to the end-device MCU.

Note

This can be achieved through any communication link, for example, Bluetooth, USB, or LPWAN, and is application-dependent.

Prerequisites for LoRa Basics™ Modem:

  • No additional requirements

Prerequisites for LoRa Basics Modem-E:

  • No additional requirements

Prerequisites for a Transceiver:

  • No additional requirements

Step-by-Step Procedure

The size of the almanac image is 2580 bytes, which is more than the LR111x can handle in one command. As a result, the almanac image must be split into multiple chunks, as described below.

  1. The application downloads a Base64-encoded string containing the almanac image from das.loracloud.com.

  2. The Base64-encoded string is decoded to obtain the almanac image.

  3. The application transfers the almanac image to the end-device.

  4. The device application splits the almanac image into chunks. The size of each chunk must be a multiple of 20 bytes, and the maximum size depends on the type of device:

  5. The device application transfers the chunks to the LR1110 through consecutive calls to the GnssAlmanacFullUpdate() command.

  6. Verifying the integrity of the downloaded almanac image also depends on device type:

    • Transceiver: The device application must read back the whole almanac after the write process and verify its integrity. This is necessary to ensure that no bit errors occurred during the SPI transactions.

    • LoRa Basics Modem-E: SPI transactions are already protected by a CRC, while integrity checking is not required it is recommended

Note

  • The application can split the almanac into chunks before transferring it to the device application.

  • All the chunks must be transferred to the LR111x through consecutive SPI transactions; that is, no other commands can be sent to the LR111x until all of the chunks have been transferred.

The almanac should be updated monthly. At the very least, it must be updated at least every three months. For LoRa Basics Modem-E, after a full almanac update has been performed (assuming the almanac image was obtained from das.loracloud.com) the almanac can be kept up-to-date more efficiently using the OTA almanac update procedure as described in LoRa Basics Almanac Update.

Used By

GNSS

Troubleshooting

  • No suggestions at this time.

References

  1. LoRa Cloud™ Device & Application Services

  2. LoRa Basics™ Modem-E Reference Manual

  3. LR1110 User Manual