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http://www.solid-run.com/wiki/Setting_the_eFuses_for_MicroSOM_and_Hummingboard

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Setting the eFuses for MicroSOM and Hummingboard

(This tutorial derived from the original SolidRun community post on the subject.

If an end-user orders a MicroSOM together with a HummingBoard carrier board, the shipping department is notified that the boot configuration needs to be set on the MicroSOM. A MicroSOM which does not undergo this process (for example, if one is ordered by itself) will need to have an appropriate configuration completed to tell the processor where to look for the start of the boot process.

This tutorial provides the information on blowing the i.MX6 eFuses on the SoC integrated on the MicroSOM in order to boot from the Micro-SD cart.Please note that this operation is irreversible.

USB host to host cable preparation

Use these instructions as a "getting started" step if you do not already have an appropriate USB OTG cable.

1. Get two usb cables.
2. Cut them in the middle or where ever it‘s convenient by leaving enough length to the USB host connectors
3. Bridge the black, white and green wires of each cable directly to each other.
4. Bridge the red (vbus) wire with a 10 ohm resistor in the middle
5. USB host to host cable is ready.

Notice - the reason for the 10 ohm resistor is to protect the CuBox-i/HummingBoard power supply or PC power supply from shortening each other since in some point (when u-boot is loaded) then the vbus of both ports is active (i.e. drive 5V).

Run MFGTool to Blow the eFuses

Some key notes to keep in mind:

• This is an irreversible process. The eFuses in the i.MX6 System on Chip application processors are set by running an electrical signal through them. This process can happen exactly once. By sending the signal through these paths, they are "fused" to a specific setting.
• This is a process for advanced users and is not typically supported by Solid Run personnel. For those users ordering standalone MicroSOM devices, this process documentation has been provided as an informational starting point.
• If you use a USB OTG cable without a custom resistor, you are operating without a safety. Initially, both the Hummingboard USB and the host USB of your Windows PC will be carrying an electrical charge. If you are plugged into the wrong port, or are otherwise connected with this dual-power mode for too long, you may damage your device.

1. The MFGTool provided by Freescale requires a Windows based PC, prefereably with an intel based chipset. (Freescale‘s detection routines in the MFGTool can be picky when it comes to chipsets.)
2. Download the zip archive and unzip it to a known location.
3. Choose the right directory according to the i.MX6 device (either solo/dual lite OR dual/quad).
4. Double click on the mfgtool2.exe
5. Connect one side of the USB host to host cable to your PC and other to the upper USB port of CuBox-i or HummingBoard carrier with the intended MicroSOM to configure connected.
6. Power up the CuBox-i / HummingBoard
7. On the Windows mfgtool2.exe you would notice a second slider that indicates that u-boot is being downloaded
8. Done. If you are using CuBox-i as a carrier for blowing fuses then the front LED will blink 3 times, the number of fuses that where blown.

Understanding the eFuse Settings

There are three fuses that SolidRun blows.

1. First at address 0x23. We set the value 0xD063. This is high 16 bits of the MAC address.
2. Second at address 0x5, the value 0x2840. This indicates to boot from SD1 (the micro SD port).
3. Third at address 0x6, the value 0x10. This indicates to the i.MX6 internal bootrom to take the boot vector from the fuses instead of OTG signals.

Note - The fuse that contains the lower 32 bits of the MAC address is programmed only after passing all the manufacturing tests.

[Quote] Freescale I.mx6 mfgtool eFuse.