We made a few dozen custom boards based on imx6ul EVK design but populated two boards with ULL chip instead of UL in order to test it. We used part number MCIMX6Y0CVM05AA, rather than MCIMX6Y2DVM05AA, which is in the ULL EVK. We assumed that only temperature grade and qualification would be the difference there.
When we boot the ULL or UL EVK board with our image, it boots up fine. Shows u-boot version on the LCD and opens X.
When we boot our custom boards with the same image, Our custom boards with UL chip boot fine and work with LCD, but the boards with populated ULL don't have any LCD graphics.
We can't test with the official SD card release because ULL image hangs at u-boot after reporting the video, maybe because we have single Ethernet, or maybe because of this LCD issue.
Note that we are using a different device trees between UL and ULL boards. Those differences are only in inclusion of imx6ul.dtsi or imx6ull.dtsi, but the section describing our hardware (including the LCD) is the same.
During boot the ULL boards don't report the display being detected.
When booting our image, the error from X server is the following:
[2374637.857] (II) LoadModule: "fbdev" [2374637.858] (II) Loading /usr/lib/xorg/modules/drivers/fbdev_drv.so [2374637.866] (II) Module fbdev: vendor="X.Org Foundation" [2374637.866] compiled for 1.18.0, module version = 0.4.4 [2374637.866] Module class: X.Org Video Driver [2374637.866] ABI class: X.Org Video Driver, version 20.0 [2374637.866] (II) FBDEV: driver for framebuffer: fbdev [2374637.874] (--) using VT number 2 [2374637.879] (WW) Falling back to old probe method for fbdev [2374637.879] (II) Loading sub module "fbdevhw" [2374637.879] (II) LoadModule: "fbdevhw" [2374637.880] (II) Loading /usr/lib/xorg/modules/libfbdevhw.so [2374637.884] (II) Module fbdevhw: vendor="X.Org Foundation" [2374637.887] compiled for 1.18.0, module version = 0.0.2 [2374637.887] ABI class: X.Org Video Driver, version 20.0 [2374637.888] (EE) open /dev/fb0: No such file or directory [2374637.888] (EE) No devices detected. [2374637.888] (EE) Fatal server error: [2374637.888] (EE) no screens found(EE) [2374637.888] (EE)
Is there any functional difference between the two ULL parts (Y0 vs Y2)?
Are there any considerations when populating the ULL chip on a UL board design? We can not spot any difference in hardware design.