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docs: Initial split of README into docs directory
The top-level README document has got pretty unwieldy and so we need to switch to add some more structure to our documentation. The first step is to split out sub-sections of the README document into separate files in a new 'docs' directory. Whilst splitting up the README, we can also take the opportunity to tidy things up and fix a couple of typos. Signed-off-by: Paul Barker <pbarker@toganlabs.com>
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Paul Barker
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Andrei Gherzan
Andrei Gherzan
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# Optional build configuration
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There are a set of ways in which a user can influence different paramenters of
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the build. We list here the ones that are closely related to this BSP or
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specific to it. For the rest please check:
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<http://www.yoctoproject.org/docs/latest/ref-manual/ref-manual.html>
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## Compressed deployed files
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1. Overwrite IMAGE_FSTYPES in local.conf
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* `IMAGE_FSTYPES = "tar.bz2 ext3.xz"`
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2. Overwrite SDIMG_ROOTFS_TYPE in local.conf
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* `SDIMG_ROOTFS_TYPE = "ext3.xz"`
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3. Overwrite SDIMG_COMPRESSION in local.conf
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* `SDIMG_COMPRESSION = "xz"`
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Accommodate the values above to your own needs (ex: ext3 / ext4).
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## GPU memory
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| Variable | Details |
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|----------------|---------------------------------------------------------------------|
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| `GPU_MEM` | GPU memory in megabyte. Sets the memory split between the ARM and |
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| | GPU. ARM gets the remaining memory. Min 16. Default 64. |
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| `GPU_MEM_256` | GPU memory in megabyte for the 256MB Raspberry Pi. Ignored by the |
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| | 512MB RP. Overrides gpu_mem. Max 192. Default not set. |
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| `GPU_MEM_512` | GPU memory in megabyte for the 512MB Raspberry Pi. Ignored by the |
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| | 256MB RP. Overrides gpu_mem. Max 448. Default not set. |
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| `GPU_MEM_1024` | GPU memory in megabyte for the 1024MB Raspberry Pi. Ignored by the |
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| | 256MB/512MB RP. Overrides gpu_mem. Max 944. Default not set. |
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## Add purchased license codecs
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To add you own licenses use variables `KEY_DECODE_MPG2` and `KEY_DECODE_WVC1` in
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local.conf. Example:
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```
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KEY_DECODE_MPG2 = "12345678"
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KEY_DECODE_WVC1 = "12345678"
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```
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You can supply more licenses separated by comma. Example:
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```
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KEY_DECODE_WVC1 = "0x12345678,0xabcdabcd,0x87654321"
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```
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## Disable overscan
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By default the GPU adds a black border around the video output to compensate for
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TVs which cut off part of the image. To disable this set this variable in
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local.conf:
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`DISABLE_OVERSCAN = "1"`
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## Set overclocking options
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The Raspberry PI can be overclocked. As of now overclocking up to the "Turbo
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Mode" is officially supported by the raspbery and does not void warranty. Check
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the config.txt for a detailed description of options and modes. Example turbo
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mode:
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```
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ARM_FREQ = "1000"
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CORE_FREQ = "500"
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SDRAM_FREQ = "500"
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OVER_VOLTAGE = "6"
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```
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## Video camera support with V4L2 drivers
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Set this variable to enable support for the video camera (Linux 3.12.4+
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required)
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`VIDEO_CAMERA = "1"`
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## Enable offline compositing support
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Set this variable to enable support for dispmanx offline compositing:
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`DISPMANX_OFFLINE = "1"`
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This will enable the firmware to fall back to off-line compositing of Dispmanx
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elements. Normally the compositing is done on-line, during scanout, but cannot
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handle too many elements. With off-line enabled, an off-screen buffer is
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allocated for compositing. When scene complexity (number and sizes
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of elements) is high, compositing will happen off-line into the buffer.
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Heavily recommended for Wayland/Weston.
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See: <http://wayland.freedesktop.org/raspberrypi.html>
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## Enable kgdb over console support
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To add the kdbg over console (kgdboc) parameter to the kernel command line, set
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this variable in local.conf:
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`ENABLE_KGDB = "1"`
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## Boot to U-Boot
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To have u-boot load kernel image, set in your local.conf:
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`KERNEL_IMAGETYPE = "uImage"`
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This will make kernel.img be u-boot image which will load uImage. By default,
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kernel.img is the actual kernel image (ex. Image).
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## Image with Initramfs
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To build an initramfs image:
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* Set this 3 kernel variables (in linux-raspberrypi.inc for example)
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- kernel_configure_variable BLK_DEV_INITRD y
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- kernel_configure_variable INITRAMFS_SOURCE ""
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- kernel_configure_variable RD_GZIP y
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* Set the yocto variables (in linux-raspberrypi.inc for example)
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- `INITRAMFS_IMAGE = "<a name for your initramfs image>"`
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- `INITRAMFS_IMAGE_BUNDLE = "1"`
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* Set the meta-rasberrypi variable (in raspberrypi.conf for example)
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- `KERNEL_INITRAMFS = "-initramfs"`
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## Device tree support
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Device tree for RPi is only supported when using linux-raspberrypi 3.18+
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kernels.
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* Set `KERNEL_DEVICETREE` (in conf/machine/raspberrypi.conf)
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- the trailer is added to the kernel image before kernel install task. While
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creating the SDCard image, this modified kernel is put on boot partition (as
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kernel.img) as well as DeviceTree blobs (.dtb files).
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NOTE: `KERNEL_DEVICETREE` is default enabled for kernel >= 3.18 and always
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disabled for older kernel versions.
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## Enable SPI bus
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When using device tree kernels, set this variable to enable the SPI bus:
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`ENABLE_SPI_BUS = "1"`
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## Enable I2C
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When using device tree kernels, set this variable to enable I2C:
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`ENABLE_I2C = "1"`
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## Enable PiTFT support
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Basic support for using PiTFT screens can be enabled by adding below in
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local.conf:
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* `MACHINE_FEATURES += "pitft"`
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- This will enable SPI bus and i2c device-trees, it will also setup
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framebuffer for console and x server on PiTFT.
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NOTE: To get this working the overlay for the PiTFT model must be build, added
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and specified as well (dtoverlay=<driver> in config.txt).
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Below is a list of currently supported PiTFT models in meta-raspberrypi, the
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modelname should be added as a MACHINE_FEATURES in local.conf like below:
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`MACHINE_FEATURES += "pitft <modelname>"`
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List of currently supported models:
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* pitft22
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* pitft28r
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* pitft35r
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## Misc. display
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If you would like to use the Waveshare "C" 1024×600, 7 inch Capacitive Touch
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Screen LCD, HDMI interface (<http://www.waveshare.com/7inch-HDMI-LCD-C.htm>) Rev
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2.1, please set the following in your local.conf:
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`WAVESHARE_1024X600_C_2_1 = "1"`
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## Enable UART
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RaspberryPi 0, 1, 2 and CM will have UART console enabled by default.
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RaspberryPi 0 WiFi and 3 does not have the UART enabled by default because this
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needs a fixed core frequency and enable_uart wil set it to the minimum. Certain
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operations - 60fps h264 decode, high quality deinterlace - which aren't
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performed on the ARM may be affected, and we wouldn't want to do that to users
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who don't want to use the serial port. Users who want serial console support on
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RaspberryPi3 will have to explicitely set in local.conf: `ENABLE_UART = "1"`.
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Ref.:
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* <https://github.com/raspberrypi/firmware/issues/553>
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* <https://github.com/RPi-Distro/repo/issues/22>
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