====== Getting started with Olimex A20-SOM ======

Interesting links:
  * https://www.olimex.com/wiki/A20-SOM
  * http://fablab-robert-houdin.org/wiki/doku.php?id=tutoriels
  * http://linux-sunxi.org/Main_Page
  * https://github.com/linux-sunxi

===== Buildroot system =====

Based on https://github.com/mireq/buildroot-a20-olinuxino, using the sunxi u-boot and Linux kernel

<code>
make a20_olinuxino_defconfig
make
</code>

===== Bootable microSD =====

Make two partitions:

  * boot partition: FAT16, starting at offset 1MB, for u-boot.img, script.bin, uEnv.txt and uImage
  * linux partion: ext3 for rootfs

> :!:  Before running below commands be sure of which device is your to-be-formatted microSD card. In this example we take ''/dev/sdc'' . You might loose data if you run the wrong command!

<code>
sudo sfdisk /dev/sdc << EOF
2048,98304,0xE,*
,,,-
EOF
</code>

Format the first partition in FAT16 for boot
<code>
sudo mkfs.vfat -F 16 /dev/sdc1 -n boot
</code>

Format the second in EXT3 for the root filesystem
<code>
sudo mkfs.ext3 /dev/sdc2 -L rootfs
</code>

Burn ''sunxi-spl.bin'' and ''u-boot.bin'', from //Buildroot//'s ''output/images'', at the beginning of the SD card:
<code>sudo dd if=sunxi-spl.bin of=/dev/sdc bs=1024 seek=8
sudo dd if=u-boot.bin of=/dev/sdc bs=1024 seek=32
</code>
or, equivalently, ''u-boot-sunxi-with-spl.bin'' (actually, the concatenation of ''sunxi-spl.bin'' and ''u-boot.bin''), to be found in //Buildroot//'s ''build/uboot'':
<code>
sudo dd if=u-boot-sunxi-with-spl.bin of=/dev/sdc bs=1024 seek=8
</code>

Copy the content of the boot partition:
<code>
tar -xvf rootfs.tar -C </path/to/boot/mount/point> --strip=2 --wildcards './boot/*' --exclude './boot/u-boot.bin' --exclude './boot/u-boot.img' --exclude './boot/sunxi-spl.bin' --exclude './boot/u-boot-sunxi-with-spl.bin'
</code>

Copy the content of the root filesystem:
<code>
sudo tar xvf rootfs.tar -C </path/to/rootfs/mount/point> --exclude 'boot'
</code>


===== Display =====

[[http://www.elecfreaks.com/wiki/index.php?title=2.2S%22_TFT_LCD:_TFT01-2.2S]]
==== SPI support ====
  - Add the spi-sun7i driver support to the linux kernel: [[http://will-tm.com/spi-on-the-cubieboard2/]] and [[https://github.com/matzrh/rfm12b-linux/blob/master/spi-sun7i.patch]]
  - Load the spi driver: ''modprobe spi_sun7i''

==== FBTFT support ====
[[https://github.com/notro/fbtft]]

(requires spi driver to be loaded)
  - Add the fbtft driver support to Buildroot: [[http://lists.busybox.net/pipermail/buildroot/2015-January/116416.html]]
  - Load the fbtft_device driver: ''modprobe fbtft_device name=rpi-display  busnum=1 gpios=reset:4,dc:5,led:6 rotate=90''
     * ''rpi-display'' is associated to the 'ili9341' driver,
     * ''busnum=1'' refers to device ''/dev/spi1.0'',
     * ''gpios=...'' makes the link between the defferents signals to the actual gpios they are connected to)
     * ''rotate=...'' indicates the rotation angle (counter clockwise) of the screen (0, 90, 180 or 270)
  - Load the driver corresponding to the screen: ''modprobe fb_ili9341''

=== Backlight ===

https://github.com/notro/fbtft/wiki/Backlight

===== Network configuration =====

==== Ethernet ====
To enable eth0 interface, load sunxi-emac driver on the OLinuXino-Lime
<code>
modprobe sunxi-emac
</code>

==== WLAN ====
=== with a rt2870 chipset ===
Add the support for the rt2870 chipset to your system:
  * make sure linux-firmware is ticked in your buildroot configuration
  * make sure Busybox mdev is configured to support firmware hotload

On target,
  * configure mdev as kernel hotplug
<code>
sysctl -w kernel.hotplug=/sbin/mdev
mdev -s
</code>
  * load the rt2800usb driver
<code>
modprobe rt2800usb
</code>
  * bring up the wlan0 interface
<code>
ifconfig wlan0 up
</code>

=== with a mt7601 chipset ===

== Build the driver ==

Download the driver sources from [[https://github.com/porjo/mt7601]]

Apply the following patch: 
<code>
diff --git a/src/Makefile b/src/Makefile
index dfe1283..b2615ab 100755
--- a/src/Makefile
+++ b/src/Makefile
@@ -197,11 +197,13 @@ endif
 
 ifeq ($(PLATFORM),PC)
 # Linux 2.6
-LINUX_SRC = /lib/modules/$(shell uname -r)/build
+LINUX_SRC = <path_to_your_linux_kernel_sources>
 # Linux 2.4 Change to your local setting
 #LINUX_SRC = /usr/src/linux-2.4
-LINUX_SRC_MODULE = /lib/modules/$(shell uname -r)/kernel/drivers/net/wireless/
-CROSS_COMPILE = 
+LINUX_SRC_MODULE = $LINUX_SRC/drivers/net/wireless
+CROSS_COMPILE = <path_to_your_sdk>/host/usr/bin/arm-linux-
+ARCH=arm
+export ARCH
 endif
 
 ifeq ($(PLATFORM),INTELP6)
diff --git a/src/include/os/rt_linux.h b/src/include/os/rt_linux.h
index 3726b9e..821e401 100755
--- a/src/include/os/rt_linux.h
+++ b/src/include/os/rt_linux.h
@@ -279,7 +279,7 @@ typedef struct file* RTMP_OS_FD;
 
 typedef struct _OS_FS_INFO_
 {
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,12,0)
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,02,0)
 	uid_t				fsuid;
 	gid_t				fsgid;
 #else
diff --git a/src/include/rtmp_def.h b/src/include/rtmp_def.h
index 2afcb77..b69af63 100755
--- a/src/include/rtmp_def.h
+++ b/src/include/rtmp_def.h
@@ -75,7 +75,7 @@
 #define RX_RING_SIZE            8
 #endif /* INF_AMAZON_SE */
 #define MAX_TX_PROCESS          4
-#define LOCAL_TXBUF_SIZE        2048
+#define LOCAL_TXBUF_SIZE        256
 #endif /* RTMP_MAC_USB */
 
 #ifdef MULTIPLE_CARD_SUPPORT
diff --git a/src/os/linux/config.mk b/src/os/linux/config.mk
index 531b00e..e67c864 100755
--- a/src/os/linux/config.mk
+++ b/src/os/linux/config.mk
@@ -1054,7 +1054,7 @@ CFLAGS := -D__KERNEL__ -I$(LINUX_SRC)/include -Wall -O2 -Wundef -Wstrict-prototy
 export CFLAGS
 endif
 
-GCCVERSION = $(shell gcc -dumpversion)
+GCCVERSION = $(shell $(CROSS_COMPILE)gcc -dumpversion)
 
 ifeq ($(PLATFORM),PC)
     ifneq (,$(findstring 2.4,$(LINUX_SRC)))
</code>

where
  - ''<path_to_your_linux_kernel_sources>'' is the path to the sources of kernel for your target; e.g. ''<buildroot_directory>/output/build/linux-sunxi-v3.4.104-r0''
  - ''<path_to_your_sdk>'' is your buildroot output directory; e.g. ''<buildroot_directory>/output''
Note that changing the ''LOCAL_TXBUF_SIZE'' define value from ''2048'' to ''256'' prevents an error to occur during the loading of your driver.

Launch the compilation:
<code>
$ cd src
$ make
</code>

and copy the generated ''src/os.linux/mt7601Usta.ko'' driver to your target.
Note that the generated file is quite big (15MB)...

== Load the driver ==
On your target:
  * load the driver:
<code>
$ insmod mt7601Usta.ko
</code>

  * enable the ''ra0'' interface:
<code>
$ ifconfig ra0 up
</code>

===== PWM =====

[[https://www.olimex.com/wiki/How_to_add_pwm]]

===== OpenGL =====

via the mali driver ([[http://linux-sunxi.org/Mali_binary_driver]])

To redirect the output the a non standard //framebuffer device//, define the ''FRAMEBUFFER'' environnement variable to the wanted device.
THe same variable has to be used to launch a Qt5 application, instead of the normal ''QT_QPA_EGLFS_FB'' one.