We have some problems on a custom board equipped with iMX6 Dual (IMX6D7CVT08AD).
The boards provides 1GB NAND FLASH (MT29F8G08ABACAH4:C).
The boards provides 1GB DDR3 DRAM (4 x H5TC2G63GFR-PBA).
We produced 300 boards.
About 75% of them have no problem and they boot correctly every power on / HW reset.
25% of them have some problems during the boot procedure. They fail booting one time on 20/30 power on.
It happen both by switch on the power of the board than by pushing reset button. Cause of it I think it is not a problem about voltage sequences at power on.
The problem is the same both from NAND Flash than SD CARD boot device. So the problem is not of the specific device.
We have BOOT_MODE0=0 and BOOT_MODE1=1 (internal Boot).
If we set boot mode as Serial Downloader, USB OTG has been always recognized by a PC so it seems a problem of some BOOT GPIO.
We have following GPIO configurations at booting:
- BOOT_CFG1 [7:0] 11000000 (NAND FLASH) 01000000 (SD)
- BOOT_CFG2 [7:0] 00000000
- BOOT_CFG3 [7:0] not connected (floating)
- BOOT_CFG4 [7:0] not connected (floating)
Could be a problem about floating BOOT gPIO?
At the moment we are using an external Watchdog HW in order to solve the problem but we would understand the cause of boot failure.