If OP can't tell the difference I wonder why it is an issue at all. On Wednesday, May 21, 2014 8:15:57 PM UTC+2, john3909 wrote: > > > From: PLyttle <[email protected] <javascript:>> > Reply-To: <[email protected] <javascript:>> > Date: Wednesday, May 21, 2014 at 10:57 AM > To: <[email protected] <javascript:>> > Subject: Re: [beagleboard] Bootloader, MLO, u-boot and boot button > > SYS_BOOT2 is present on P8-43. I would try to place a resistor between > this point and ground first. The Pull-up is pretty weak (100kOhm), so > something like 10 k would probably do the job. Off course this pin is also > used as LCD_DATA2, but if you can live with it, it is a lot better than > moving R93-R68 on the board > > If you don’t have the correct tools to move 0402 components then your > solution might be better. Try it and see if it works. How do you plan to > see which MLO (eMMC or SDCard) is loaded at boot time? > > Regards, > John > > > > On Wednesday, May 21, 2014 7:34:34 PM UTC+2, john3909 wrote: >> >> >> From: Alberto Potenza <[email protected]> >> Reply-To: <[email protected]> >> Date: Wednesday, May 21, 2014 at 3:00 AM >> To: <[email protected]> >> Subject: [beagleboard] Bootloader, MLO, u-boot and boot button >> >> Dear all, >> I have some problems trying to understand how the boot procedure is in >> the Beaglebone Black. >> I saw several posts around but it is quite hard for me to fully >> understand how it works. So, sorry if I am repeating something that most of >> you already know. >> What I've understood so far (I hope...) is: >> 1) if I just power my BBB, the boot procedure is based on the flash >> placed on the BBB. It means that the ROM Bootloader of the AM335xx loads >> the MLO from the flash, the u-boot.img from the flash and then "all the >> rest" starts. >> 2) if I power my BBB and I push the Boot-button, the ROM Bootloader of >> the AM335xx loads the MLO and the u-boot.img and "all the rest" from the SD >> card. The AM335xx does not talk at all with the flash during all the boot >> procedure. >> 3) if I try to modify the uEnv.txt in the SD card in such a way to force >> the OS to be loaded form the SD card, wich means >> >> mmc dev 1 >> mmc rstn 1 >> gpio set 52 >> optargs=capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN,BB-BONE-EMMC-2G >> etc..etc >> >> and I do not push the boot button, the AM335xx loads the MLO and the >> u-boot.img from the flash and "only after that" it will loads the uEnv.txt >> file from the SD card. It means that the bootloader will search a MLO and >> u-boot.img in the flash -> they will talk for a while and after that the >> AM335xx will loads the uEnv.txt from the SD. >> >> Now, I would like to have the point number two without to push the boot >> button: I do not want the AM335xx to talk with the flash at all and I am >> not pretty sure it is possible. In my opinion there are two ways: >> the former is to set the resistor on the BBB in such a way to have the >> same configuration as the boot-button pressed (hardware way). The latter is >> to erase completely the flash in such a way to have no MLO and u-boot.img >> in it. However, the second way could not work because the AM335xx will talk >> with the flash trying to find MLO and the u-boot.img, while I do not want >> them to talk each other. >> >> Is it all correct? >> >> Your understanding is correct. The bootloader looks for MLO with a >> specific header on the eMMC and if it does not find one, it looks for an >> MLO on the SDCard. If you look at sheet 6 in the BBB schematics, there is a >> table which shows the boot order given the SYSBOOT settings. If you don’t >> want the BBB to access the eMMC at boot time, you must move resistors on >> the board as you indicated. >> >> Regards, >> John >> >> >> >> Thanks a lot. >> >> Alberto >> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to the Google Groups >> "BeagleBoard" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. >> >> -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > For more options, visit https://groups.google.com/d/optout. > >
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