Raspberry Pi

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https://www.raspberrypi.org/documentation/hardware/computemodule/RPI-CM-DATASHEET-V1_0.pdf

 Booting Steps

  • When the Raspberry Pi is first turned on, the ARM core is off, and the GPU core is on. At this point the SDRAM is disabled.
  • The GPU starts executing the first stage bootloader, which is stored in ROM on the SoC. The first stage bootloader reads the SD card, and loads the second stage bootloader (bootcode.bin) into the L2 cache, and runs it.
  • bootcode.bin enables SDRAM, and reads the third stage bootloader (loader.bin) from the SD card into RAM, and runs it. [ More recent versions do not use a third stage bootloader. ]
  • [ If applicable ]loader.bin reads the GPU firmware (start.elf).
  • start.elf reads config.txt, cmdline.txt and kernel.img

loader.bin doesn't do much. It can handle .elf files, and so is needed to load start.elf at the top of memory (ARM uses SDRAM from address zero). There is a plan to add elf loading support to bootcode.bin, which would make loader.bin unnecessary, but it's a low priority (I guess it might save you 100ms on boot). [ This change has since taken place. ]

https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=6685#p85064



Accessing Raspberrypi without connecting it with monitor and keyboard


Terminal: enter the command ssh pi@raspberrypi


If this FAILS, try finding out what IP address is assigned to the Raspberry Pi from Router Admin Panel. Look up the device named something like raspberrypi and copy the IP address. Paste it into the command you tried from above where it now states raspberrypi.

create an 'ssh' file without any extension in 'boot' folder of sd card to enable ssh access.

connect to a wireless router create another file called "wpa_supplicant.conf" which contains the following info

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=US

network={
 ssid="Your network SSID"
 psk="Your WPA/WPA2 security key"
 key_mgmt=WPA-PSK
}
Edit the country code, SSID and the WPA/WPA2 key with the info you need to connect to your network.


Qemu 

https://azeria-labs.com/emulate-raspberry-pi-with-qemu/

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