COM AM335x Linux

Linux virtual machine for development

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

Building your own 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 and build the linux kernel using 5 threads and a build directory

1. Start a terminal on Linux

2. # git clone https://github.com/dh-electronics/linux-am33x.git

3. # mkdir build

4. # cd linux-am33x

5. # git checkout release/20160219 # checkout latest/required release branch

6. # ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- make O=../build/ am335x_dhcom_defconfig

7. # ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- make O=../build/ menuconfig (optional: If you want to add/remove Kernel features)

8. # ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- make -j5 O=../build/ zImage

9. # ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- 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 with U-Boot

Please refere to the DHCOM Update Mechanism for i.MX6.

Update the kernel in 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. Restart the system (e.g. reboot)

Debian Rootfilesystem

Available Rootfilesystems

Please have a look at the iMX6 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 ttymxc0 dhcom login: root Password: foo

Shutdown

# shutdown -h now

Calibrating the touchscreen (only on Debian 6.0)

# 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

DHCOM (FF) UART 1	/dev/ttymxc0
DHCOM (BT) UART 2	/dev/ttymxc4
DHCOM (STD) UART 3	/dev/ttymxc3

I2C Interfaces

dhcom3B = Hardware revision 300

DHCOM I2C 1	/dev/i2c-1
DHCOM I2C 2	/dev/i2c-0
On Module Devices	/dev/i2c-2

old: dhcom2B = Hardware revision 200

DHCOM I2C 1	/dev/i2c-0
DHCOM I2C 2	/dev/i2c-1
On Module Devices	/dev/i2c-2

SPI Interfaces

DHCOM SPI 1	/dev/spidev0.2
DHCOM SPI 2	/dev/spidev1.0

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 i.MX6 doesn‘t boot with the current schematic.

MMC/SD/eMMC Interfaces

DHCOM SD-Interface	/dev/mmcblk0pX
on module µSD Card	/dev/mmcblk1pX
on module eMMC	/dev/mmcblk2pX

'X' has to be replaced with the partition number

Control the display brightness

Coming soon

Control GPIOs

DHCOM Name:	alt. DHCOM Name:	SO-DIMM Pin#	Linux <GPIO#>
GPIO A		154	2
GPIO B		156	4
GPIO C		162	5
GPIO D		163	163
GPIO E		164	101
GPIO F		165	116
GPIO G		167	91
GPIO H		173	103
GPIO I		175	104
CIF HSYNC	GPIO J	74	174
CIF PCLK	GPIO K	72	175
CIF MCLK	GPIO L	70	105
CIF VSYNC	GPIO M	68	192
CIF D9	GPIO N	66	193
CIF D8	GPIO O	64	149
CIF D7	GPIO P	62	205
CIF D6	GPIO Q	60	18
CIF D5	GPIO R	58	16
CIF D4	GPIO S	56	17
CIF D3	GPIO T	54	19
CIF D2	GPIO U	52	20
CIF D1	GPIO V	50	146
CIF D0	GPIO W	48	147

Remark: Depending on your board configuration some of the additional gpios shared with the camera interface are not available on your system.

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 package containing can-utils (ARM)

Parallel Address- / Databus

To use the 16-bit address / databus from Linux userspace you can use the UIO driver interface. To enable and configure the interface it is necessary to setup the i.MX6 WEIM controller with the device tree. See the documentation of the device tree bindings of weim here.

Here is an example code which demonstrates how to do enable and configure the WEIM interface (parallel address- / databus):

&weim { pinctrl-names = "default"; pinctrl-0 = <&pinctrl_dhcom_weim &pinctrl_dhcom_weim_cs0 &pinctrl_dhcom_weim_cs1>; #address-cells = <2>; #size-cells = <1>; /* it is necessary to setup 2x 64MB otherwise setting gpr fails */ ranges = <0 0 0x08000000 0x04000000>, // Chip select 0 == DHCOM CS A <1 0 0x0c000000 0x04000000>; // Chip select 1 == DHCOM CS B fsl,weim-cs-gpr = <&gpr>; status = "okay"; uiomap_cs0@0,0 { compatible = "generic-uio"; reg = <0 0x00000000 0x04000000>; reg-names = "uio_cs0"; interrupt-parent = <&gpio1>; interrupts = <2 2>; // Add gpio A == interrupt #address-cells = <1>; #size-cells = <1>; fsl,weim-cs-timing = <0x00610089 0x00001002 0x0F011061 0x00000000 0x0F068A31 0x00000000>; status = "okay"; }; uiomap_cs1@0,1 { compatible = "generic-uio"; reg = <1 0x00000000 0x04000000>; reg-names = "uio_cs1"; interrupt-parent = <&gpio1>; interrupts = <4 2>; // Add gpio B == interrupt #address-cells = <1>; #size-cells = <1>; fsl,weim-cs-timing = <0x00610089 0x00001002 0x0F011061 0x00000000 0x0F068A31 0x00000000>; status = "disabled"; }; };

We have already written some demo code at /arch/arm/boot/dts/imx6qdl-dhcom_cfg-weim.dtsi. It is easy to enable in the matching device-tree file:

• /arch/arm/boot/dts/imx6s-dhcom3B-pdk2.dts
• /arch/arm/boot/dts/imx6dl-dhcom3B-pdk2.dts
• /arch/arm/boot/dts/imx6d-dhcom3B-pdk2.dts
• /arch/arm/boot/dts/imx6q-dhcom3B-pdk2.dts

- // #include "imx6qdl-dhcom_cfg-weim.dtsi + #include "imx6qdl-dhcom_cfg-weim.dtsi

To use the generic uio driver it has to be enabled in the kernel configuration (make menuconfig)

• Device Drivers -> Userspace I/O Drivers -> Userspace I/O platform driver with generic IRQ handling

The device-tree of_id of the uio driver has to be set via kernel command line

• Add "optargs='uio_pdrv_genirq.of_id=generic-uio'" to uLinuxEnv.txt

Example for a UIO userspace driver:

• uio_access.cpp
• for further information have a look at the paper Userspace I/O drivers in a realtime context

Configure your own display

To configure your own display you have to do the following steps:

1. Type in the display values into the device tree file /arch/arm/boot/dts/imx6qdl-dheva01.dtsi

• Where in the file?

Parallel display:	display@di0
LVDS display:	&ldb
Remarks: If you don't want to use both interfaces comment the unwanted out! The frame buffer resolution depends on the higher display resolution of both displays

• 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 device tree dtb files ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- make dtbs

3. Copy the dtb files onto your boot partition /dtbs (SD, µSD or eMMC)

The built imx6xx-dheva01.dtb device tree files will you find in arch/arm/boot/dts

Additional Information

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