i.MX6UL cannot boot from eMMC when LCD is connected

[nithish]

Hi,

We have designed a i.MX6UL board based on the EVK. We are facing board not booting from eMMC when LCD is connected. The LCD we are using is the same LCD which comes with the i.MX6UL EVK.

USDHC1 - SD Card
USDHC2 - eMMC

Boot configuration:

LCD Connection:
.

Case1 : When LCD is connected, board boots from SD Card.

Scope capture BT_CFG1(0) - BT_CFG1(7)

Once the processor is reset and the boot ROM starts to execute the lines are pulled high to low is what we see in the captured scope data. 

Case2 : When LCD is connected, board does not boot from eMMC .

Scope capture BT_CFG1(0) - BT_CFG1(7)

In this case the lines are not being pulled low as in case1 and case3.

Case3 : When LCD is NOT connected, board boots from  eMMC based on boot mode setting.

Scope capture BT_CFG1(0) - BT_CFG1(7)

It is not clear if i.MX6UL reset is complete and ARM core started execution of Boot ROM code and hangs while trying to access eMMC OR i.MX6UL reset does not happen and ARM core did not start execution of Boot ROM Code.

Thank You

Nithish A N

[igorpadykov]

Hi Nithish

please check sect.4 Avoiding Board Bring-up Problems

Hardware Development Guide for the i.MX 6UltraLite Applications Processor

http://cache.freescale.com/files/32bit/doc/user_guide/IMX6ULHDG.pdf
Also one can attach jtag and check  SRC_SBMR1,2 registers,

try to disconnect some lcd lines to find which one causes misbehaviour.

Best regards
igor
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[nithish]

Hi Igor,

I found that the reset is not completed when the LCD is connected. The POR_B is asserted once the PMIC voltages are settled as expected but the processor does not reset, when i tried to measure the POR_B voltage suddenly the board started booting. So when the LCD is connected the POR_B needs a trigger or something for the board to start booting. Is it due to less current? we are using  MC32PF3001A7EP PMIC.

And i also found that when the LCD data lines DATA4 TO DATA13 are disconnected the board boots without any trouble in this case the reset is happening perfectly.

Thank You

[igorpadykov]

Hi Nithish

one can check if POR line is broken or connected to other signal

Best regards
igor