COM AM335x Linux

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Linux virtual machine for development

Linux Kernel

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

How to build a Kernel

Get sources from Github

1. Start a terminal on Linux
2. # git clone
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


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)


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


Debian GNU/Linux 8 dhcom ttyO0

dhcom login: root
Password: foo


# shutdown -h now

Calibrating the touchscreen (tslib has to be installed)

# source # 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 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.
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

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:

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