Optimal boot flags setting for fail-safe way out on iMX6

[Astralix]

Hallo,

we designed some systems based on iMX6Solo and iMX6DL and we use a single eMMC to store everything. My question is now, if we program the boot flags in OTP to boot from eMMC, what is the best way to recover the device if something or someone has destroyed the u-boot in the eMMC? Cause if one sets the flag to prefer OTP before resistors, the device will not come back up on the USB OTG port especially not, if the u-boot has been destroyed only partly. So which pin to populate on the PCB and which flag in OTP needs to be set so one can always force the device to accept a new loader via USB OTG interface?

Thank you for a hint!

Kind regards

Ulrich

[igorpadykov · Accepted solution]

HI Astralix

first it may be recommended to enable wdog,

also after boot fail iROM jumps to Serial Downloader mode.

Note by default Manufacture Mode is enabled, please check

sect.8.11 SD/MMC Manufacture Mode i.MX6SDL Reference

Manual (rev.2  5/2015)

http://cache.freescale.com/files/32bit/doc/ref_manual/IMX6SDLRM.pdf

Best regards

igor

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[Astralix]

Thank you Igor,

we reversed our boot logic and use the resistor settings to boot from eMMC. If that fails (erased or non-programmed boards) automatically the OTP settings take over and force the SOC in OTG mode. In case of partly correct boot code (hang-up in boot), we can set a jumper to force use of OTP by BMODE1 and the board can be recovered via imx_usb_loader.

Best regards

Ulrich