COM AM335x Linux

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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)