Check fusing of Apalis i.MX6Q 1GB

I have obtained a used Apalis Module and created a carrier Board back in university (don‘t know if it is working a 100%)
My Problem is that I do not know whether the module is working either:
I get a somewhat normal linux boot and access to uboot on uart1 but I cannot put the module in recovery (if I do so there is just nothing on the uart1 at all) and I do not get any response or usb enumeration on the OTG-Port (can be fault of the carrier board but should not)

My question is: how can I check the fuses of the module or is there some kind of summary how they should look like? (Maybe there is something configured which prevents e.g. recovery)
I do know the ‚fuse read‘ command for uboot but have no idea which bank I have to check or which values would be correct.

Please help…I would really like to continue playing around with this interesting platform

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To check the fuses on an Apalis iMX6Q 1GB module, you can indeed use the U-Boot fuse read command. However, it’s important to proceed with caution as reading and especially writing to the fuses can have irreversible effects on your module.

The i.MX6 series of processors, which includes the Apalis iMX6Q, uses fuse banks that are documented in the i.MX6 Reference Manual provided by NXP. These fuse banks contain various configuration settings, including those for boot configuration, security features, and other specific settings that can affect the module’s operation.

To read the fuses via U-Boot, you typically use the command in the following format:

fuse read <bank> <word>

For the Apalis iMX6Q, you might be particularly interested in the following banks:

  • Bank 0: Contains the BOOT_CFG fuses that define the boot device and sequence. This could influence the ability to enter recovery mode.
  • Bank 1: Often contains fuses related to the processor’s configuration and security settings.

However, without specific knowledge of what you’re looking for or trying to achieve, it’s challenging to provide exact fuse locations and expected values. The default state of fuses can vary based on the module’s production batch and specific configurations set by Toradex during manufacturing.

If you’re concerned about the module’s ability to enter recovery mode or other operational issues, it’s typically more effective to focus on symptoms and behaviors rather than attempting to audit the fuse state directly. Since you mentioned that you have access to U-Boot, you can use this environment to investigate the module’s state further, check for error messages during boot, and ensure that the boot arguments and environment variables are correctly set for your configuration.

Remember, modifying fuse values can permanently disable the module or certain features, so any actions should be taken with a clear understanding of the consequences.

Best regards,
Toradex AI Assistant

Please, also check if these links can help you solve your problem:

Txx Recovery Mode | Toradex Developer Center.

When the module is in recovery mode, nothing is output on the debug UART until you successfully start image downloading over USB OTG. So, what you see is expected behavior. Problems with USB OTG enumeration could be due to a wrong cable connection, poor cable quality, or incorrect carrier board configuration. By the way, could you please specify which carrier board you have?

Details about fuses can be found in Chapter 7 Fusemap of the i.MX 8QuadMax Applications Processor Reference Manual. Information about fuse manipulation commands in U-Boot can be found here.

What is strange is, that neither the D+ nor the D- are pulled to 3.3V (measured with no device connected ofc) but the reference schematics do not show such a pullup even though it should be necessary for working usb-communication. Is this an indication of an via efuse deactivated otg-port?

Internal iMX SOC pull-ups controlled by firmware provide the appropriate pull-up on D lines.
Please check if your board design is done according to our Colibri Carrier Board Design Guide