COM iMX6 Linux

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Linux virtual machine for development

Building your own Kernel

Sources for the i.MX6 Kernel

How to build a kernel:

1. Start the Console on Linux
2. git clone https://github.com/dh-electronics/linux-imx6qdl.git
3. cd linux-imx6qdl
4. ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- make imx6_dhcom_defconfig
5. ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- make menuconfig (optional: If you want to add/remove Kernel features)
6. ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- make dtbs
7. ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- make zImage
  • The built imx6x-dhcom#Y-BOARD.dtb device tree files will you find in arch/arm/boot/dts
    • x = s, dl, d, q
    • # = 2 for HW200, 3 for HW300
    • Y = B for Base, H for Hi-Speed-Interfaces
    • BOARD = pdk1, pdk2, ...
  • The built zImage kernel file will you find in arch/arm/boot

Update the kernel with U-Boot

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

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 to the path /boot/dtbs
4. Check fdtfile variable in /boot/uLinuxEnv.txt (e.g. fdtfile=/dtbs/imx6dl-dhcom3B-pdk2.dtb / see above)

Reboot System

5. Restart the system (e.g. reboot)

Debian Rootfilesystem

Available Rootfilesystems

Please have a look at the iMX6 Downloads section.

External 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:

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: 
- // #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:

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

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