On Thu, Mar 26, 2015 at 2:18 PM, Joel Sherrill <joel.sherr...@oarcorp.com> wrote: > On 03/26/2015 11:35 AM, Jarielle Catbagan wrote: >> >> It looks like the internal ROM-based bootloader looks for a secondary >> program loader (SPL) that initializes the necessary devices to >> continue the boot process and pass control to a third-stage >> bootloader. So now I believe it's a matter of finding whether there >> are existing code implementations of this SPL, or last-case scenario >> this would have to be implemented. Time for more investigating. :) >> > My off the top of my head recommendation is to document the > sequence the BB goes through during initialization. Then > start with a goal of replacing U-Boot in that sequence with > Micromonitor. This keeps us in the world of at least documented > with code. However U-Boot has to be formatted, linked, etc. > is exactly what you will have to do with your Micromonitor. > > U-Boot can be a reference but not a source of code. > > The previous stages may be able to be replaced later but > I wouldn't worry about that now. >> >> On Thu, Mar 26, 2015 at 9:27 AM, Jarielle Catbagan >> <jcatbaga...@gmail.com> wrote: >>> >>> To put things into context in regards to the conversation that I was >>> having with Ed, Dr. Joel, and Gedare: >>> >>> I am currently in the process of looking into porting MicroMonitor to >>> the Beaglebone Black. As indicated by Ed, "[t]he difficulty of the >>> port will depend on how much existing CPU-initialization >>> (clocks, cache, etc..) code we can reuse." >>> > Ed and the authors of the RTEMS code would have to agree but, > in principle, anything in the Beagle BSP should be fair game for > reuse in Micromonitor. > Yeah you have to get explicit permission, the RTEMS license is not compatible to the Micromonitor one in that direction.
>>> Ed has also indicated to me that there might be an internal bootloader >>> stored in a ROM-based memory that might look for an image in a >>> specific format. I will definitely be investigating more into this. >>> I did manage to briefly browse through the Beaglebone Black System >>> Reference Manual Rev C.1 [1], and I have found that the boot >>> configuration/process is briefly elaborated in section 6.7. For >>> convenience, since it's a short section I will post it here: >>> >>> "The design supports two groups of boot options on the board. The user >>> can switch between these modes via the Boot button. The primary boot >>> source is the onboard eMMC device. By holding the Boot button, the >>> user can force the board to boot from the microSD slot. This enables >>> the eMMC to be overwritten when needed or to just boot an alternate >>> image... >>> >>> [T]the processor-external boot code is composed of two stages. After >>> the primary boot code in the processor ROM passes control, a secondary >>> stage (secondary program loader -- "SPL" or "MLO") takes over. The SPL >>> stage initializes only the required devices to continue the boot >>> process, and then control is transferred to the third stage "U-boot". >>> Based on the settings of the boot pins, the ROM knows where to go and >>> get the SPL and UBoot code. In the case of the BeagleBone Black, that >>> is either eMMC or microSD based on the position of the boot switch." >>> >>> I was kindly guided to look into programming a uSD card as it might be >>> more efficient to run MicroMonitor off of the uSD for quick testing >>> after every build. If all goes well, either an application image will >>> be located and booted off of the same SD card or via a network boot. >>> For serial debugging I have an FTDI 3.3V USB-to-Serial cable that I >>> have been previously using to access the U-boot monitor on the >>> Beaglebone Black. >>> > This is how we do a lot of our testing. It isn't worth the effort > to put something on the board itself. Plus it places wear and > tear on a replaceable item, not on the built-in flash. >>> >>> [1] >>> https://github.com/CircuitCo/BeagleBone-Black/blob/master/BBB_SRM.pdf?raw=true >> >> _______________________________________________ >> devel mailing list >> devel@rtems.org >> http://lists.rtems.org/mailman/listinfo/devel > > > > -- > -- Joel Sherrill > Ask me about RTEMS: a free RTOS > Support and Training Available > > > _______________________________________________ > devel mailing list > devel@rtems.org > http://lists.rtems.org/mailman/listinfo/devel _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
