Flashing firmware compiled using MBED Online/Offline compiler causes CRC Errors.

[Ajay K]

I am building my application using the MBED online/offline compiler and again the same error has cropped up that was occurring earlier when mbed 6 was released. I am getting CRC errors as shown below, when flashing the MDot module using tera term and ymodem interface. I am using the mDot library 4.0.1 to compile my custom firmware and also mbed-os-6.1.0. I am getting the CRC error no matter which compiler I use.

Below is the CRC Error I get in both cases.

upgrade ymodem
[INFO] Starting upgrade
[INFO] Starting YMODEM file transfer
[INFO] YMODEM file transfer succeeded
[INFO] appended crc: 0
[INFO] calculated crc: 614595670
[ERROR] File validation failed

Here is my mbed_app.json contents to merge the bootloader.

{
    "macros": [
        "FOTA"
    ],
    "target_overrides": {
        "*": {
            "target.printf_lib": "std"
        },
        "MTS_MDOT_F411RE": {
            "target.console-uart-flow-control": null,
            "platform.stdio-baud-rate": 115200,
            "platform.default-serial-baud-rate": 115200,
            "target.app_offset": "0x10000",
            "target.bootloader_img": "bootloaders/mdot-bootloader.bin"
        }
    }
}

Thanks,
Ajay

[Ajay K]

Any thoughts, this issue is blocking us from testing 4.0 mdot library.

Thanks,
Ajay

[Taylor Heck]

With mbed-os 5 a post-build script combined bootloader and application into one image as well as appending a CRC. With mbed-os 6 this is no longer the case.

We have a Pyhton tool that can be used to append the CRC https://pypi.org/project/mtsmultitool

Also note that older MDot bootloader versions expected the firmware image to also have a bootloader included. The newer bootloader assumes the upgrade image does not include a bootloader.

The mbed-cli will output a *_application.bin image which should be used for YMODEM upgrades. The multitool program can be used to strip a bootloader from the image if needed.

Appending CRC:
> multitool device crc -o output.bin fw_application.bin

Strip bootloader and append CRC:
> multitool device plain -b 0x10000 -c -o outut.bin fw.bin

[Ajay K]

Thanks Taylor for taking the time to respond to this issue. I just need to ensure I understand your comments clearly for the offline build scenario.

The bootloader I have called out in the mbed_app.json gets packed with the final version of the bin file, however you are saying that I should use the fw_application.bin that is generated during the offline build instead, append the CRC using the python tool multitool and using the command below:

Appending CRC:
> multitool device crc -o output.bin fw_application.bin

The second scenario is that for the online compiler scenario? Where you are suggesting we strip the bootloader off the resulting *.bin file that is created and then append the CRC using the tool?

Strip bootloader and append CRC:
> multitool device plain -b 0×10000 -c -o outut.bin fw.bin

Thanks,
Ajay

[Taylor Heck]

Yes, that’s correct.

Offline you’ll get both a combined image and an application only image.

Images from the online compiler will have the bootloader combined and it will need to be stripped when upgrading over YMODEM.

[Ajay K]

Thanks a lot Taylor for your help, the issue is resolved now.

Thanks,
Ajay

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