Enter USB Serial Download from Software

[moose]

How can we enter USB Serial Download mode from software on a device with iMX8MNANO soc? The BOOT pins are set for boot from fuse bits, which are blown for internal boot on MMC.

To enter USB Serial Download mode today, we have to alter BOOT pins in hardware that are not easily accessible. I am wondering if there is a way to do it from u-boot. This thread refers to bmode command bit, but it is not available on my SoC. I'm not sure if there is a way to enable it. Another option is to somehow corrupt or erase the working image, which forces the bootloader to switch to USB serial download mode. Please let us know if this is possible. Thanks!

[rudi_cyber · Accepted solution]

You can type fastboot <usb id> under u-boot to get  into download mode. 

For example, fastboot 0  or fastboot 1 depeneds on your hardware design. 

[moose]

That worked. Thank you.

One thing to note is the protocol detected by uuu is FB (fastboot) and not SDPS. I don't know if this presents any issues but I was able to program the image.

I am assuming with this method you can't update U-boot, correct?

[Rita_Wang]

Recommend you to go to the  USB Serial Download mode by hardware way, boot mode is easy to control and will also set for boot up mode.