Modem FOTA Questions (Firmware compatibility matrix and firmware file storage)

[droberson]

Hello,

I am evaluating the nRF9161 and nRF9151 and have a few questions.

1. In regard to modem FOTA delta firmware updates, where is the delta file stored in both Serial LTE modem (SLM) and non-SLM cases? Is it stored in the modem core flash, or must it be stored in the application core flash or external flash? I have read conflicting information on the DevZone regarding this.

2. When updating to a new modem major firmware version in non-SLM mode via FOTA, say 1.3.x to 1.4.x, this requires a "full" modem firmware update and requires storing the firmware file in external flash due to its size. If you design a product without an external flash, is it true you are then stuck on whatever major version you program and deploy the modem with since you cannot perform a "full' firmware update? Ie, if you are on 1.3.x you can never go to 1.4.x via FOTA?

3. When the modem is used as a Serial LTE modem (SLM), does the modem only support delta firmware updates, or can you also perform a full modem firmware update? If it doesn't support full modem firmware updates in this mode, then are you stuck on whatever modem major version you deploy your product with?

4. Based on the nRF9160 modem firmware compatibility matrix linked below, newer modem firmware versions are not compatible with older versions of the nRF connect SDK. Is this true?

For example, if you are on modem firmware 1.3.1 and nRF Connect SDK 2.0.0, it doesn't seem like you can jump directly to modem firmware 1.3.6 because it isn't compatible with nRF Connect SDK 2.0.0. It seems like you you can only jump to modem firmware 1.3.2 because 1.3.3 isn’t compatible with nRF Connect SDK 2.0.0. Once you jump to modem firmware 1.3.2, you then update to nRF Connect SDK 2.1.0. This will then let you update to modem firmware 1.3.4 (skipping 1.3.2). Then you can update nRF Connect SDK to 2.2.0, which will then let you update the modem firmware to 1.3.6.

Are these incremental updates really necessary?

https://infocenter.nordicsemi.com/topic/comp_matrix_nrf9160/COMP/nrf9160/nrf9160_modem_fw.html

Edit: I have a bonus question not related to FOTA. Please let me know if I should create a new post for this.

5. Do the Nordic cellular modules support multiple carriers with a single eSIM or SoftSIM? If so, how do you add carrier profiles to each SIM type and switch between profiles? I didn't see any AT commands detailing this.

Thanks,

Derek

[Charlie]

Hi Derek,

Thanks for checking with us. For your questions:

1. In regard to modem FOTA delta firmware updates, where is the delta file stored in both Serial LTE modem (SLM) and non-SLM cases? Is it stored in the modem core flash, or must it be stored in the application core flash or external flash? I have read conflicting information on the DevZone regarding this.

Not sure where you read the conflicting information, but these are clearly explained in the following document in page for modem firmware(MFW) Delta firmware updates (nordicsemi.com). You should distinguish modem and serial lte modem(SLM) application. SLM FOTA is same as normal application, and its MFW FOTA is same as all other nRF91 based applications.

During a firmware delta update, the application transfers the firmware into an area of flash memory in the modem, known as the scratch area. A delta update is a binary file, with a .bin extension. The update file is named in such a way that both the source and destination firmware versions can be identified, for example, mfw_nrf9160_update_from_1.2.2_to_1.2.3. Modem delta update files are part of the official modem releases and can be found in the nRF9160 modem firmware zip file or nRF91x1 LTE firmware zip file depending on the SiP you are using.

2. When updating to a new modem major firmware version in non-SLM mode via FOTA, say 1.3.x to 1.4.x, this requires a "full" modem firmware update and requires storing the firmware file in external flash due to its size. If you design a product without an external flash, is it true you are then stuck on whatever major version you program and deploy the modem with since you cannot perform a "full' firmware update? Ie, if you are on 1.3.x you can never go to 1.4.x via FOTA?

Yes, this is true, you need to take this into consideration when you design the hardware.  

If you need to perform a major version update (for example, v1.2.x to v1.3.x), you need an external flash with a minimum size of 4 MB.

3. When the modem is used as a Serial LTE modem (SLM), does the modem only support delta firmware updates, or can you also perform a full modem firmware update? If it doesn't support full modem firmware updates in this mode, then are you stuck on whatever modem major version you deploy your product with?

SLM #XFOTA command functional support full modem firmware update, but there is a minimum 4 MB external flash requirement for hardware. Yes, the device will stuck on major version if device does not support full modem update.

FOTA AT commands (nordicsemi.com):
Start FOTA for full modem update. Can only be used when the overlay-full_fota.conf configuration file is used.

Not supported on the Thingy:91 or nRF9160 DK board revisions older than 0.14.0 as they lack an external flash to store the firmware image. See nRF9160 DK board revisions for more details. Also, not currently supported on Thingy:91 X.

4. Based on the nRF9160 modem firmware compatibility matrix linked below, newer modem firmware versions are not compatible with older versions of the nRF connect SDK. Is this true?

Depends on how old NCS is, you can find from the table that a MFW version will support quite many NCS versions and there will be overlap between MFW and NCS versions.

The compatibility means we have done comprehensive tests with the list combination. You can still use the latest MFW with a very old version NCS Or the opposite, but we can not guarantee there is no problem with this combination, so this is not suggested usage. 

See the latest in Modem firmware (nordicsemi.com).

5. Do the Nordic cellular modules support multiple carriers with a single eSIM or SoftSIM? If so, how do you add carrier profiles to each SIM type and switch between profiles? I didn't see any AT commands detailing this.

Yes, Nordic cellular modules do support multiple carriers with a single eSIM or SoftSIM.

The modem can handle the switching of profiles automatically. You can use the standard +CSIM and +CRSM commands for this purpose. However, the detailed procedure should be provided by your SIM card provider. Adding a new profile on the eSIM is handled automatically by the SIM card provider's system and the SIM card. The modem provides the necessary communication channels for this. You can refer to the GSMA eSIM Whitepaper for more details on this process. The traditional carriers (not MVNOs like iBasis or Onomondo) do not allow their profiles to be provisioned or uploaded into SoftSIMs. These carriers need to use profiles from SoftSIM providers like Onomondo. 

Best regards,

Charlie

[droberson]

Hey Charlie,

Thanks for the detailed responses, they are much appreciated and helpful.

Charlie said:

Not sure where you read the conflicting information

One Devzone post implied that the delta firmware file is stored in the application core flash. Per the source link below: "to large to be stored in the application flash".

Source:  nrf9160 FOTA modem updates 

Hence my confusion. I had not seen the link you shared until now, so thanks for sharing! Good to know that it is stored in the modem flash and not the application flash.

Charlie said:

SLM #XFOTA command functional support full modem firmware update, but there is a minimum 4 MB external flash requirement for hardware.

Ah, I see now. I missed the line in the SLM AT command document for XFOTA that states "Start FOTA for full modem update. Can only be used when the overlay-full_fota.conf configuration file is used". My apologies.

To preface my questions below, I am not familiar with Zephyr, so please excuse my ignorance. I am only familiar with the old nRF SDK (Non-Zephyr).

Question: For full modem FOTA to work in SLM mode, does the user supplied external flash need to be connected directly to the nRF91 and managed by the nRF91 application core? In other words, there is no way to store the modem firmware file in an external flash connected to the host MCU and then feed this to the modem via AT commands over the UART?

Question: Is there an example for SLM full FOTA that uses the overlay-full_fota.conf file that I can reference? Perhaps even a matching schematic reference design?

Question: Does Nordic provides a complete pre-built solution for a Serial LTE Modem including a reference design schematic and application core binary or is it still up to the user to manage the application core of the nRF91 in SLM mode?

Charlie said:

You can still use the latest MFW with a very old version NCS Or the opposite, but we can not guarantee there is no problem with this combination, so this is not suggested usage. 

So it it up to the user to test and confirm compatibility for combinations that are not in the compatibility matrix. Got it, thanks!

Derek