Hello everyone, I just received a Udoo board and started playing with it. In the beginning, everything is perfect. I flashed my SD card follow this link. It works well. The OS was booted successful and I can control the board via serial console as well as web interface. Unfortunately, I'm facing a trouble after tried to build a custom kernel and copy the new zImage file to SD card. Detail: I wanna write a driver to control HD44780 LCD via a PCF8574A IO expansion module. Follow the other guide, I regenerated configuration to enable PCF857x driver, modified device tree, then rebuilt zImage and device tree blob files. The compilation was successful and I just copied zImage and dtb files to SD card and reset the board. However, the red LED always light stable. I checked serial connection and found that boot process was stuck after u-boot completed its responsibility: Code: U-Boot SPL 2015.04-21123-g7271b51 (Jul 22 2016 - 14:15:22) Setting 1024MB RAM calibration data port 1 SPL: u-boot second stage will be loaded from MMC0 U-Boot 2015.04-21123-g7271b51 (Jul 22 2016 - 14:15:22) CPU: Freescale i.MX6SX rev1.2 at 792 MHz CPU: Temperature 48 C Reset cause: POR Board: UDOO Neo Full I2C: ready DRAM: 1 GiB PMIC: PFUZE3000 DEV_ID=0x30 REV_ID=0x11 MMC: FSL_SDHC: 0, FSL_SDHC: 1 *** Warning - bad CRC, using default environment In: serial Out: serial Err: serial Net: using phy at 0 FEC0 [PRIME] Normal Boot Hit any key to stop autoboot: 0 switch to partitions #0, OK mmc0 is current device reading uEnv.txt 163 bytes read in 10 ms (15.6 KiB/s) Running bootscript from mmc ... Device Tree: dts/imx6sx-udoo-neo-full-hdmi-m4.dtb ## Error: "m4boot" not defined reading /zImage 4237600 bytes read in 216 ms (18.7 MiB/s) Booting from mmc ... reading dts/imx6sx-udoo-neo-full-hdmi-m4.dtb 46020 bytes read in 34 ms (1.3 MiB/s) Kernel image @ 0x80800000 [ 0x000000 - 0x40a920 ] ## Flattened Device Tree blob at 83000000 Booting using the fdt blob at 0x83000000 Using Device Tree in place at 83000000, end 8300e3c3 Switched to ldo_bypass mode! Starting kernel ... I didn't see anything after the "Starting kernel ..." line. I'm a newbie and I don't have any experience to investigate this issue. I have searched for something similar in the forum but no one seems to have encountered my problem. Did I miss something? I wanna clarify that I'm only set CONFIG_GPIO_PCF857X in .config file, re-compile zImage and dtb files. Do I need to re-compile u-boot? And someone can tell me how to investigate when encountering similar problems, please? Thank you.