From: steve <sg...@wi...> - 2011-01-18 03:21:24
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Hello, I need to change the first boot device tested from the mmc card to NAND flash. My application is a bare-metal task which must start as soon as possible after POR ( < 100ms). The current search for the device with X-loader is USB->UART3->MMC1->NAND I need X-loader in NAND, but with the above scan, it takes at least 400 msec before it has tested the first three devices and finally loads X-loader from flash. The scan sequence sequence I need is NAND->USB->UART3->MMC1 (On the Beagleboard this is the normal sequence - which can be overridden by pressing a push button during reset -- which then gives the the same scan sequence as the Overo). With that scan sequence and X-loader in NAND on Beagle board, the X-loader, "Texas Instruments X-Loader..." message prints out after only 45ms! The difference in the boot scan sequence is caused by the SYS.BOOT[5] pin. In the Overo it is high and in the Beagleboard it is low. I don't know if there is any way to access to that pin on the Overo. I looked at the board and I see there are a number of non-populated resistor locations. It is my hope that one of them is connected to SYS.BOOT[5] and that putting a resistor there and to ground as well as removing the resistor now used to pull-up SYS.BOOT[5] will give me the NAND-first boot I need. Does anyone know if this is possible? and where the change needs to be made? I would really appreciate it!!! Thanks Steve |