Our basic problem is getting our iMX536 hardware into the boot mode after reset is de-asserted. It is currently programmed per the iMX53 dev board GPIO pin configuration to boot from the sdcard but it never attempts to read the sd card. If we understand the boot mode sequence if it can't identify the selected boot device it will default to the serial boot mode but we never see it respond during the 32 sec WD timeout to anything sent on the serial port. we have not re-programmed boot mode 0 and 1 for forced serial boot yet.
We have developed our own hardware around the iMX536 based on the iMX53 development board. Schematics in PDF format are available
The board incorporates the MC34078 PMIC per the development board with the same power sequencing.
Board is an 8 Layer board with 4 signal, 4 power per Dev board and User's guide specs.
The Ethernet interface was removed on our board. The USBOTG is being used and we have access to one serial port through a diagnostics header.
Our board uses DDR3 per the development board
Our board uses both camera inputs to the iMX536 but currently nothing is connected.
All power rails are correct. All probed at the dogbone via directly under the CPU BGA
All clocks are present (24MHx XTAL on iMX536, 32kHz on PMIC with 32kout to iMX536
nRESET_IN and nPOR only comes up after rails are stable
Boot Mode is configured using GPIO
Boot Mode0 and mode 1 are pulled low for boot from SD Card
Boot config lines when reset is de-asserted are all correct and identical to iMX53 dev board
A separate reset pushbutton was added so a hard reset could be generated to make sure a reset was provided after clocks and power were stable.
The 24MHz CPU crystal on XTAL/EXTAL is oscillating at the correct frequency and from appoximatle 1.2V down to zero. The only difference we see between our board and the dev board is our 24MHz oscillator does not start until about 10mS after nPOR is de-asserted while the dev board starts during the nPOR rise time. If a subsequent nPOR assertion is applied after the clock is running however our board still does not do anything.
All relevant signals seem to be the same as the dev board at power-on reset other than the 24MHz osc timing.
We are looking for assistance in what we may have missed or overlooked in trying to bring this hardware up. If there is some minor difference between the iMX536 and the iMX535 on the dev board or missing some interaction between the CPU and PMIC that would prevent it from seeking the correct boot device.