= render "pages/arm/menu"

%h1= title "How to configure Qemu"

%h2 Target Pi on Mac
%p So even the idea is to run software on the Pi, not everyone has a Pi (yet :-)
%p Others, like me, prefer to develop on a laptop and not carry the Pi around.
%p For all those, this here explains how to emulate the Pi on a Mac.
%p
  Even if you have a Pi,
  =link_to "this explains",  "remote_pi.html"
  a nice way to develop with it.

%p
  We'll more or less follow a
  =ext_link "blog post", "https://blog.agchapman.com/using-qemu-to-emulate-a-raspberry-pi/"
  i found, with small additions.

%h3 Qemu
%p
  Get the Qemu. There may be other emulators out there, and i have read of armulator,
  but this is what i found described and it works and is “easy enough”.
%pre
  %code
    :preserve
      brew install qemu

%h3 Pi images

%p
  Create a directory for the stuff on your mac, ie pi.
  %pre
    %code
      mkdir pi

  pi is in the gitignore, and the scripts in bin, will assume pi.

%p
  Get the latest Raspian image. The
  =ext_link "lite version" "https://www.raspberrypi.org/downloads/raspbian/"
  without Gui is fine, and smaller.
%p
  Change the file format with something like:
  %pre
    %code
      qemu-img convert -f raw -O qcow2 2017-08-16-raspbian-stretch-lite.img raspbian-stretch-lite.qcow
  So we can then resize the file, without it taking extra space
  %pre
    %code
      qemu-img resize raspbian-stretch-lite.qcow +6G
  Put the resulting file into the pi directory.

%h3 Kernel
%p
  One still needs a kernel (even there is one on the image?), and Druv kindly keeps a
  repository of them. Since we downloaded the stretch image, grap the
  =ext_link "stretch kernel" , "https://github.com/dhruvvyas90/qemu-rpi-kernel/raw/master/kernel-qemu-4.9.59-stretch"
  and also the mysterious
  =ext_link "tdb file." , "https://github.com/dhruvvyas90/qemu-rpi-kernel/raw/master/versatile-pb.dtb"
  Both go into the pi directory.

%h3 Boot
%p
  There is quite a bit to the command line to boot the pi. There is a script in the bin
  directory, but here it is:
%pre
  %code
    :preserve
      qemu-system-arm -kernel pi/kernel-qemu-4.9.59-stretch -dtb pi/versatile-pb.dtb -cpu arm1176 -m 256 -M versatilepb -no-reboot -serial stdio -append 'root=/dev/sda2 panic=1 rootfstype=ext4 rw' -hda pi/raspbian-stretch-lite.qcow -net nic -net user,hostfwd=tcp::2222-:22
%ul
  %li the cpu is what broadcom specifies, ok
  %li memory is unfortunately hardcoded in the versatilepb “machine”
  %li the kernel is the file name of the kernel you downloaded (or extracted)
  %li raspbian.img is the image you downloaded. Renamed as it probably had the datestamp on it
  %li the "-net user,hostfwd=tcp::2222-:22" redircts the port 2222 to let you log into the pi
%p So
%pre
  %code
    :preserve
      ssh -p 2222 -l pi localhost
%p will get you “in”. Ie username pi (password raspberry is the default) and port 2222
%p Qemu bridges the network (that it emulates), and so your pi is now as connected as your mac.

%h3 Working on the pi
%p
  You'll probably want to log in by ssh at some point. If for no other reason than
  Ctl-C will stop the emulator when you are logged in, and not the program you are
  running on the emulator. This gets old _really_ quickly.
%p
  To configure the ssh server on the pi, log in and run
  %pre
    %code
      sudo raspi-config
  and enable ssh in the interface options.
  There is another text on how to
  =link_to "work on" , "/arm/remote_pi.html"
  the pi. Off course google is good , and raspian site can help too.

%h2#links Links
%ul#selector
  %li=ext_link "Post used for instructions", "https://blog.agchapman.com/using-qemu-to-emulate-a-raspberry-pi/"
  %li=ext_link "stretch kernel" , "https://github.com/dhruvvyas90/qemu-rpi-kernel/raw/master/kernel-qemu-4.9.59-stretch"
  %li=ext_link "Rasbian image file", "http://www.raspberrypi.org/downloads/"