u-blox Memory Housekeeping Issue on XBee3 Cat M Cellular


u-blox has informed Digi of an issue for SARA-R410M-02B using previous firmware version L0. app version A.02.00. A new firmware release is available (L0. app version A.02.01) and is applied in u-blox production with first shipments beginning 21 Dec 2018. The following guidelines and recommended actions are applicable to affected fielded product using previous firmware version (L0. app version A.02.00.)

This u-blox module is a component in the Digi XBee3 LTE-M/NB-IoT Cellular Smart Modem (XB3-C-A2-UT-001). 

The issue can cause memory corruption which renders the u-blox cellular component unusable. 

This issue can occur when a device is put to sleep or power cycled within 20 seconds of a scheduled memory maintenance procedure. The memory maintenance procedure occurs every 124 days after the first network registration of the device. 

Devices that do not sleep and do not periodically power cycle have a low risk of occurrence.  



Affected Products

This issue affects the following Digi products: 

  • XB3-C-A2-UT-001 - Digi XBee3 Cellular Smart Modem, LTE-M/NB-IoT (rev. G and older)
  • XK3-C-A2-UT-U - Digi XBee3 Cellular Smart Modem, LTE-M, AT&T (rev. G and older)
  • XK3-C-N1-UT-E - Digi XBee3 Cellular Smart Modem, NB-IoT Development Kit (rev. D and older)


Customer Resolution


Firmware should be updated on all affected modules that have not been patched for this issue. Firmware update options are below. XBee modules shipped after May 15, 2019 should contain u-blox firmware app version A.02.01 and do not need to be updated. 

Firmware Update Options: 

1.  USB Direct

    Update u-blox firmware over USB direct mode with the u-blox EasyFlash Firmware Download Tool. u-blox firmware application version should be updated to A.02.01. You can find a link to the update instructions on the product support page under "Firmware Updates" (select u-blox A.02.01 EasyFlash Update)

2.  UART

   Update u-blox firmware over standard XBee UART (pins 2 and 3). Update scripts are title “u-blox Over the Wire Update Script” in the “Firmware Updates” section at the following support page:

3.   Firmware Over-The-Air (cellular)

    Update u-blox firmware over the air (FOTA) using Digi Remote Manager (DRM). Update scripts are title “u-blox Over the Air Update Script” in the “Firmware Updates” section at the following support page:

  • The XBee must be updated to the latest XBee firmware (11417, 11416, 11415, 11413,11412, 1012, 11312, or 31012 depending on the XBee model).
  • The end product host controller must not put the XBee to sleep or power down the XBee during a firmware update. This should be accomplished through two-way communication and negotiation between the host and the XBee and should not be attempted with a set timer. 
  • For XBee used without a host controller, the XBee must be set to stay awake for the duration of the update.
  • Digi Remote Manager (DRM) is required for remote firmware upgrades over the air. If a DRM subscription is not in place, a subscription may be activated remotely if the Device Options (DO) AT command has set to 1 in the XBee. If this bit has been set 0, it can only be set to 1 again via communication from the host controller to the XBee.*


*Note that in the latest firmware other options may also need to be set to establish a connection as the new default is to not connect, but to simply query DRM over UDP.


Product that has already encountered this failure mode should be returned to Digi through the normal RMA process.

Last updated: Jul 04, 2019

Filed Under

RFRF Dev kits

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