Before a Raspberry Pi 3 will boot from a mass storage device, it needs to be booted from an SD card with a config option to enable USB boot mode. This will set a bit in the OTP (One Time Programmable) memory in the Raspberry Pi SoC that will enable booting from a USB mass storage device. Once this bit has been set, the SD card is no longer required. Note that any change you make to the OTP is permanent and cannot be undone. 0738login:Penguin2018/04/06(金) 09:31:29.70ID:1snhLa0w 一回きり・・・ 気軽に試すものじゃないな。 0739login:Penguin2018/04/06(金) 10:37:13.10ID:a4WLdODf それ、ビット立てるprogram_usb_boot_modeの逆のオプションが用意されてないだけなのか 本当に一度書いたら書き直せないメモリなのかよくわからんよね
New update makes it possible to boot from USB drives and networks.
It is now possible to boot a Raspberry Pi 3 from a USB storage device or directly from a network connection. These new boot modes enable Pi owners to start up Raspberry Pi 3 devices with alternatives to the traditional SD card. The Pi can now be booted from an attached USB storage device, such as a hard drive, SSD drive or thumb drive. You can even boot a Raspberry Pi without any storage device attached, by loading the operating system from another computer on the same network. 0757login:Penguin2018/04/09(月) 17:15:10.85ID:ARmxEEY/ The boot process “There’s a small boot ROM, which is an unchanging bit of code used to boot the device,” explains Gordon Hollingworth, Raspberry Pi’s director of engineering, in his blog on the Raspberry Pi site (magpi.cc/2bdmnhY). “It’s the boot ROM that can read files from SD cards and execute them. “When the Pi is powered up, or rebooted, it tries to talk to an attached SD card,” he continues. “[It] looks for a file called bootcode.bin; if it finds it, then it loads it into memory and jumps to it. This piece of code then continues to load up the rest of the Pi system, such as the firmware and ARM kernel.” 0758login:Penguin2018/04/09(月) 17:16:19.69ID:ARmxEEY/ The potential to boot to the Raspberry Pi was included at the New update makes it possible to boot from USB drives and networks hardware level with the Raspberry Pi 3. “While squeezing in the quad A53 processors, I spent a fair amount of time writing some new boot modes,” reveals Gordon. “Needless to say, it’s not easy squeezing SD boot, eMMC boot, SPI boot, NAND flash, FAT file system, GUID and MBR partitions, USB device, USB host, Ethernet device, and mass storage device support into a mere 32kB. ” He notes that this boot mode hasn’t been enabled by default, as they first wanted to check that it worked as expected. The boot modes are enabled in one-time programmable (OTP) memory, so you need to enable the boot mode on your Raspberry Pi 3 first. This is done using a config.txt parameter. Unfortunately, the new boot options are only available in the Raspberry Pi 3 ? you can’t USB or Ethernet-boot a Pi Zero or older models. “The boot code is stored in the BCM2837 device only,” says Gordon, “so the Pi 1, Pi 2, and Pi Zero will all require SD cards.” 0759login:Penguin2018/04/09(月) 21:05:18.35ID:3rFpgY1R すごーい 0760login:Penguin2018/04/09(月) 21:30:49.75ID:7HLCKS+j お〜！これはほんとに すごい だね(笑)
