Can someone explain the SPI switch to me?

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Damian
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Can someone explain the SPI switch to me?

Post by Damian »

This may be a very stupid question, but can anyone explain the SPI switch to me?

I initially thought that the switch was to switch between booting from the eMMC or the microSD card. However, with the switch in the same position, it seems that it will boot from the eMMC when there's no microSD card in place, and will boot from the microSD card when there in one there.

So, what is the SPI setting? What is it for and what does it do?

This may become clearer to me once I've updated the SPI (which I'm struggling to do, but another thread tells me that it may be the cause of some problems that I'm having), but in the meantime, I'd love to read some clarification.

Thanks,
Damian
Odroid N2+ with CoreELEC

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tobetter
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Re: Can someone explain the SPI switch to me?

Post by tobetter »

Please refer to the link for the boot sequence,
https://wiki.odroid.com/odroid-n2/softw ... t_sequence

SPI is actually a type of memory and it contains small Linux system a.k.a "Petitboot" on ODROID-N2, that's a sort of boot manager to start an OS from a storage attached to ODROID-N2, USB/SD/eMMC. The SPI switch let you select what's the primary boot media, SPI flash memory or "MMC" as printed on the board. Why not eMMC or SD is when you flip the boot select switch to "MMC" the boot order is predefined by SoC. eMMC is always higher priority than SD card. So CPU fetch the bootloader from eMMC and start to boot, if there is no bootloader then fetch from SD. That's on order predefined by Amlogic SoC.

If you do not need to manage and use more than one OS, you would not need to use the boot select switch since you can boot from eMMC or SD. But if you like to run more than two OS, you will want to select one of them and Petitboot in the SPI flash memory will help this. What if you want to boot from USB storage? Actually USB storage is not the device what SoC can make a boot, but the Petitboot can load the boot blobs from USB storage to start an OS.

Using SPI flash is your option to use ODROID-N2 widely for your purpose. If you do not need the complicate system, only to run single OS from eMMC or SD, ignore the Petitboot.

Please add your doubt if necessary, somebody will explain more in better English. :)
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odroid (Thu Nov 19, 2020 10:37 am) • harddroid (Wed Dec 02, 2020 7:15 am)

Damian
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Re: Can someone explain the SPI switch to me?

Post by Damian »

That's great, thanks.
Odroid N2+ with CoreELEC

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