Is the I2C register PowerOff() function dangerous?


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Main - Homebrew discussion - Is the I2C register PowerOff() function dangerous?

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d0k3

Posted on 11-04-15 08:12 PM (rev. 3 of 11-04-15 08:13 PM)

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I mean this one:

void PowerOff()
{
    i2cWriteRegister(I2C_DEV_MCU, 0x20, 1 << 0);
    while (true);
}

On Github, @idgrepthat wrote:

Posted by idgrepthat on Github
Don't recommend. Power functions are unstable and can potentially brick.

Posted by idgrepthat on Github
Reboot has never caused problems for me, but homebrew and Gw's power-off functions can cause 3ds's to behave strangely. Like return 0 causing a full power-off in dsi mode instead of the homemenu grey screen that's expected. Yellows8 bricked his 3ds while researching these registers.

Maybe it's something you still feel is worth it, but I think it's an unnecessary risk given the small reward. I'm not that concerned about it because I never use homebrew power off any more. Your call.

I think the shutdown functions of CTR Boot Manager and Quick Shutdown are different, because they don't operate on ARM9. Anyways, is there any more infos on the subject? A shutdown function would be pretty convenient, but it is of course not worth the price of messing up your 3DS.

plutoo

Posted on 11-04-15 08:26 PM

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I'm pretty sure it's safe. There are two things that can cause a brick with MCU pokes (afaik). They are as follows:

1. Power cycle from ARM11 when ARM9 has things left that it hasn't yet written to NAND. This could corrupt the file-system, internal files could become out-of-sync, and whatnot.
2. Poking around with LED pattern registers (this was how Yellows8 bricked his 3DS).

In this case neither applies so I'd say go for it.

d0k3

Posted on 11-10-15 10:55 AM

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Posted by plutoo
I'm pretty sure it's safe. There are two things that can cause a brick with MCU pokes (afaik). They are as follows:

1. Power cycle from ARM11 when ARM9 has things left that it hasn't yet written to NAND. This could corrupt the file-system, internal files could become out-of-sync, and whatnot.
2. Poking around with LED pattern registers (this was how Yellows8 bricked his 3DS).

In this case neither applies so I'd say go for it.

Thanks for your reply! Well, I tried it, and in fact it is now included as a hidden option in Decrypt9. I still find it suspicious, though. With that option, the console turns of so fast and also a big difference to the reboot function, which takes it's time. Don't know if I will keep that in. I'd prefer to do it the same way as f.e. Quick Reboot does it, but I also have no access to CTRUlib functions from Decrypt9.

Main - Homebrew discussion - Is the I2C register PowerOff() function dangerous?

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