How to boot BBB using GPMC Interface using Bare Metal Programming...

What is using the GPMC bus?

C

I want to first boot BBB using a custom NOR Cape [GPMC Interface]. NOR Cape will hold configuration files for logi bone. I will use bare metal programming.

The place where I am doubtful is that if I try and boot BBB with my NOR Flash using GPMC controller, can it conflict with eMMC functionally or electrically? Whether resetting eMMC is a must when using the shared lines as GPMC bus?

These lines of SRM of BBB of scetion 8.1.2 bother me:-

BEFORE the SW reinitializes the pins, it MUST put the eMMC in reset. This is done by taking eMMC_RSTn (GPIO1_20) LOW after the eMMC has been put into a mode to

enable the reset line. This pin does not connect to the expansion header and is accessible only on the board.

DO NOT automatically drive any conflicting pins until the SW enables it. This puts the SW in control to ensure that the eMMC is in reset before the signals are used from the

cape. You can use a GPIO pin for this. No, we will not designate a pin for this function. It will be determined on a cape by cape basis by the designer of the respective cape.

With these lines as per my understanding I will never be able to boot from GPMC...

These lines of SRM of BBB of scetion 8.1.2 bother me:-

BEFORE the SW reinitializes the pins, it MUST put the eMMC in reset. This is done by taking eMMC_RSTn (GPIO1_20) LOW after the eMMC has been put into a mode to

enable the reset line. This pin does not connect to the expansion header and is accessible only on the board.

DO NOT automatically drive any conflicting pins until the SW enables it. This puts the SW in control to ensure that the eMMC is in reset before the signals are used from the

cape. You can use a GPIO pin for this. No, we will not designate a pin for this function. It will be determined on a cape by cape basis by the designer of the respective cape.

With these lines as per my understanding I will never be able to boot from GPMC...

As I understand, the interface is shared with the logi-bone cape. A spi is used to reset the the eMMC but not the NOR flash. This is a problem. You really need to use one only of these capes and not both. I will say electrically only the logi-bone can be on not either eMMC or NOR flash!

C

Hi Clem,

I will detail further, I want to program or interface logi bone using I2C interface and SPI Interface on P9 connector of BBB. But I want to boot from my NOR CAPE on GPMC bus.

The thing that comes in between is the eMMC on BBB which I want to isolate. Can i boot from GPMC bus using my NOR CAPE and still isolate eMMC?

This is where I am confused. I do not want GPMC Interface for Logi Bone.

Further I will do this using starterware and hence no OS for me..