COM AM335x Linux

Linux virtual machine for development

• Please have a look at: Virtual Machine for Application Development

Linux Kernel

Sources for the DHCOM AM335x Linux Kernel v4.1.x

• The latest Linux Kernel source code is available on GitHub: https://github.com/dh-electronics/linux-am33x

How to build a Kernel

Get sources from Github 1. Start a terminal on Linux 2. # git clone https://github.com/dh-electronics/linux-am33x.git 3. # cd linux-am33x 4. # git checkout release/20160719 # checkout latest/required release branch Configure and build the kernel using 5 threads and a build directory 5. # mkdir ../build 6. # ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make O=../build/ am335x_dhcom_defconfig 7. # ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make O=../build/ menuconfig (optional: Add/Remove Kernel Features) 8. # ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make -j5 O=../build/ zImage 9. # ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make -j5 O=../build/ dtbs Your new zImage file is available in ../build/arch/arm/boot The Devicetree file am335x-dheva01.dtb is available in ../build/arch/arm/boot/dts

Update the Kernel and Devicetree with U-Boot

Please refere to the DHCOM Update Mechanism for am335x.

Update Kernel and Devicetree on a running Linux

Kernel 1. Copy the kernel zImage file to the path /boot 2. Check whether the correct zImage file name is set in /boot/uLinuxEnv.txt (e.g. zImage_file=zImage) Devicetree 3. Copy the devicetree file am335x-dheva01.dtb to the path /boot/dtbs 4. Check fdtfile variable in /boot/uLinuxEnv.txt (e.g. fdtfile=/dtbs/am335x-dheva01.dtb) Reboot System 5. Restart the system (e.g. reboot)

Debian Rootfilesystem

Available Rootfilesystems

Please have a look at the DHCOM AM335x Downloads section.

External Documentation

• The Debian Administrator's Handbook: A reference book presenting the Debian distribution, from initial installation to configuration of services. The administration and configuration chapters apply to our Debian based root filesystems.
• Debian Documentation

Login

Debian GNU/Linux 8 dhcom ttyO0 dhcom login: root Password: foo

Shutdown

# shutdown -h now

Calibrating the touchscreen (tslib has to be installed)

# source setup_tslib.sh # setup environment for use of tslib # ts_calibrate

• Check the enviroment variable "TSLIB_TSDEVICE=/dev/input/event0" with printenv if an error occurs.

How to create a microSD-card with a rootfilesystem on it

1. Format a microSD card like following (in linux e.g. gparted, palimpsest) with Master Boot Record partition scheme

P1 ext3, name="boot" (Primary partition: 100MiB) P2 ext3, name="rootfs" (Primary part.: Residual space)

2. Untar the root file system to the "rootfs" partition of the microSD card (Don't copy the tar archive directly to the microSD card)

Start the Console on Linux # su # chmod 755 /path/of/the/microSD_card # cd /path/of/the/microSD_card # tar xfjv path/to/RootFS/Name_of_RootFS_file.tar.bz2

Remark: If you got a *.tar.gz file so type tar xfzv ... to extract the rootfilesystem.

Kernel Userspace Interfaces to Access Hardware

Serial (UART) Interfaces

Interface	Kernel 4.1.x	Kernel > 4.4.x
DHCOM UART 1 (Rx Tx Rts Cts)	/dev/ttyO0	/dev/ttyS0
DHCOM UART 2 (Rx Tx)	/dev/ttyO1	/dev/ttyS1
DHCOM UART 3	not available	not available

I2C Interfaces

DHCOM I2C 1	/dev/i2c-2
DHCOM I2C 2	not available
On Module Devices	/dev/i2c-0

SPI Interfaces

DHCOM SPI 1	/dev/spidev1.1
DHCOM SPI 2	not available

Remark: DHCOM SPI1 interface doesn‘t work with DHCOM Premium Developer Kit (HD00013).

Reason: At DHCOM Premium Developer Kit SPI 1 isn‘t connected, because otherwise AM335x doesn‘t boot with the current schematic.

MMC/SD/eMMC Interfaces

DHCOM SD-Interface	/dev/mmcblk0pX (optional)
on module µSD Card	/dev/mmcblk0pX (optional)
on module eMMC	/dev/mmcblk1pX

'X' has to be replaced with the partition number

DHCOM SD-Interface or on module µSD slot is available

Control the display brightness

echo [0..8] > /sys/class/backlight/backlight/brightness

Control GPIOs

DHCOM Name:	alt. DHCOM Name:	SO-DIMM Pin#	Linux <GPIO#>
GPIO A		154	20
GPIO B		156	115
GPIO C		162	116
GPIO D		163	65
GPIO E		164	114
GPIO F		165	112
GPIO G		167	111
GPIO H		173	7
GPIO I		175	113
CIF HSYNC	GPIO J	74	117
CIF PCLK	GPIO K	72	57
CIF MCLK	GPIO L	70	56
CIF VSYNC	GPIO M	68	55
CIF D9	GPIO N	66	54
CIF D8	GPIO O	64	51
CIF D7	GPIO P	62	50
CIF D6	GPIO Q	60	49

Remark: The parallel camera interface is not available on DHCOM AM335x.

Export

echo <GPIO#> >/sys/class/gpio/export

Remark: Have a look into /sys/class/gpio/ for already configured gpios.

Set direction

echo in >/sys/class/gpio/gpio<GPIO#>/direction

echo out >/sys/class/gpio/gpio<GPIO#>/direction

Set state

echo 0 >/sys/class/gpio/gpio<GPIO#>/value

echo 1 >/sys/class/gpio/gpio<GPIO#>/value

Initialize and Test CAN Interface

Initialize:

ip link set can0 up type can bitrate 500000

Send test message via cansend (part of can-utils):

cansend can0 100#11.2233.44556677.88

Receive can messages (part of can-utils):

candump can0

Get can-utils:

• Debian Jessie (armhf): apt-get install can-utils
• Debian Squeeze (armel):Debian package containing can-utils (ARM)

Configure your own display

To customize the devicetree to support your display please follow these steps:

1. Type in the display values into the device tree file arch/arm/boot/dts/am335x-dhcom.dtsi

• Where in the file?

Parallel display:

&panel

• How?

Here is an example:

display-timings { DataImage_7inch_FG0700G3DSSW { clock-frequency = <33260000>; hactive = <800>; vactive = <480>; hback-porch = <86>; hfront-porch = <42>; vback-porch = <33>; vfront-porch = <10>; hsync-len = <128>; vsync-len = <2>; hsync-active = <0>; vsync-active = <0>; de-active = <1>; pixelclk-active = <1>; }; };

2. Build the devicetree dtb files ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make dtbs
3. Copy the dtb files into your /boot partition /dtbs (SD, µSD, eMMC, or NAND)

Additional Information

• Linux Kernel Features
• Embedded Linux Build Environment (ELBE)