Building an i.MX Development Environment (uuu Edition) | Technical Column

Overall flow

The overall process from setting up the Yocto development environment, building an image file, writing it to the i.MX evaluation board, and verifying functionality is as follows:

1 Preparation: Setting up the host machine
2 Let's build a development environment: Build a development environment with Yocto
3 Let's try building it: Build the image
4 Let's try writing: Write the generated image to the evaluation board
5 Let’s check the startup: Check that the evaluation board starts up
6 Let's check the functionality: Check the actual operation on the evaluation board

In the previous column, we introduced steps 1 to 3. In this column, we will introduce steps 4 to 5 ("3. Let's try writing" and "4. Let's check the startup"), and step 6 will be introduced in the next column.

Flow of building an i.MX development environment using Yocto

Review of last time and what we will prepare this time

In the previous column, we created a Yocto Project build environment on the host machine and built an image for the i.MX evaluation board. The evaluation board we used was the i.MX 8M Plus (8MPPLUSLPD4-EVK).

Reference image: i.MX 8M Plus (8MPPLUSLPD4-EVK)

• Reference URL: 8MPLUSLPD4-EVK
• Reference URL: i.MX Yocto Project User's Guide
• Reference URL: Embedded Linux for i.MX Applications Processors

Let's try writing

Before writing the image file to the evaluation board, consider how to start (boot) the evaluation board. According to the reference manual, the following boot devices are supported.

The boot devices for the evaluation board are listed below.

In this column, we will write an image file via serial download to the microSD card attached to the evaluation board and boot it. We will use a microSD card of about 32 GB.

Supplementary Note: An 8GB microSD will be sufficient for the image file used in this column, but if you are self-building applications on the evaluation board you will be developing on, you may need a microSD of 32GB or more.

We have confirmed that a microSD of 128GB capacity will work.

4. Write

We will explain how to write using uuu.
Insert the microSD card into the evaluation board and connect the host machine and the USB-C terminal on the evaluation board with a USB cable.

Figure: Connection diagram between host machine and evaluation board

If you want to use uuu to write an image file to a microSD card, you will need to install uuu on your host machine.

https://github.com/nxp-imx/mfgtools/releases
Download uuu (the latest version, Release uuu_1.5.182, at the time of writing this column) from here.

$ cd ~/Download $ wget https://github.com/nxp-imx/mfgtools/releases/download/uuu_1.5.182/uuu

Change the attributes of the downloaded file and copy it to /user/bin

$ chmod +x uuu $ sudo cp uuu /usr/bin

See below for the command details.

command	Content
chmod +<permission> <file>	Sets <permission> on <file>
<permission>	Assign values or permissions
	Number	authority	Content
	0		No permission
	1	x	Executable
	2	w	Writeable
	3	wx	Write and execute
	4	r	Readable
	5	rx	Can be read and executed
	6	rw	Read and write allowed
	7	rwx	Read, write and execute
<file>	File name
cp <file1> <file2>	Copy from <folder/file> to <folder/file>

Operate the Boot Switch (4-bit DIP switch) on the upper left of the evaluation board to set the BOOT MODE to Serial Download “0001.”

Table Boot Switch and BOOT MODE of Evaluation Board

Boot Switch	BOOT MODE
0000	Boot From Fuse
0001	Serial Download
0010	eMMC / SDHC3
0011	MicroSD / SDHC2
0100	NAND 256 page
0101	NAND 512 page
0110	QSPI 3B Read
1000	ECSPI Flash
1110	Infinite Loop

Once the hardware is ready, power up the evaluation board and begin programming.

$ cd ~/imx-yocto-bsp/build/tmp/deploy/images/imx8mp-lpddr4-evk $ sudo uuu -b sd_all imx-image-full-imx8mp-lpddr4-evk.wic.zst

If "Success 1" appears on the screen, the writing was successful.

uuu (Universal Update Utility) for nxp imx chips -- libuuu_1.5.182-0-gda3cd53 Success 1 Failure 2:1-1F0A3000 6/ 6 [Done ] FB: done

See below for the command details.

command	Content
uuu <command> <device> <file>	Write file in specified way
<command>	-b write
<device>	emmc	Write to the boot partition of the eMMC
	emmc_all	Write image file to emmc
	fat_write	Write the file to the uboot of the running board
	namd	NAND Write image file to NAND Flash
	qspi	Write image file to QSPI NOR Flash
	sd	Write to the boot partition on the SD card
	sd_all	Write the image file to the SD card
	spl	Start SPL and uboot

There are other commands, but we will not cover them in this article. For details, please refer to the following.

Reference URL: nxp-imx/mfgtools

Once programming is complete, turn off the power to the evaluation board.

Check that the image file you wrote starts up.

When the evaluation board with the image file written to it starts up, it outputs startup information via serial communication and to the display. Here we will check whether the evaluation board has started up correctly using serial communication and display output.

To boot from microSD, set the Boot Switch on the evaluation board to “0011” and change the BOOT MODE to MicroSD/SDHC2.

As shown in the diagram below, connect the DEBUG terminals of the host machine and evaluation board with a USB-micro B cable, and connect the display and evaluation board with an HDMI cable.

Figure: Connection diagram between host machine and evaluation board

1. Check the startup from the DEBUG terminal of the evaluation board

Install gtkterm on the host machine to read boot information from the DEBUG terminal (USB micro).

$ sudo apt install gtkterm $ sudo gtkterm

Once gtkterm is running, select "Configuration" → "Port" and configure serial communication. "Port" will vary depending on the host machine environment, but on the host machine used in this column it was "/dev/ttyUSB2".

Power on the evaluation board and confirm that the following text is displayed in gtkterm. This is a message sent by the evaluation board to the DEBUG terminal via serial communication, and indicates that the image file written to the evaluation board started up without any problems.

～～～omission～～～ imx8mp-lpddr4-evk login:

If the above message does not appear, please check the gtkterm settings again. In most cases, the communication port recognized by the host machine has not been selected correctly in gtkterm, so set the correct connection destination.

2. Check the display to see if it's booting

You can also check from the display whether the evaluation board has started up correctly with the image file you wrote. If the following screen appears on the display, there is no problem with the start-up. *This is not a required item for checking the start-up.

Conclusion

In this column, we explained how to write an image file to an evaluation board and check whether the image file can boot up without any problems.

In the next issue, we will check the functions and operation of the started evaluation board and image file (LINUX). We will explain how to check the operation of various functions installed on the evaluation board using the written image file, so we hope you will be able to get a closer idea of actual development.

The NEXTY Electronics Development Department provides product development and technical support using the i.MX series, so please feel free to contact us.