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BBB: Added a README that currently elaborates how to boot from SD and…
… UART.
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| Getting Started with uMon for the Beaglebone Black | ||
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| ======================================================================= | ||
| Booting: | ||
| ======================================================================= | ||
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| ----------------------------------------------------------------------- | ||
| SD Card: | ||
| ----------------------------------------------------------------------- | ||
| The Beaglebone Black can boot uMon from an SD card using two different | ||
| boot modes. The first boot mode is to boot using "raw" mode. The | ||
| second boot mode is to boot from a FAT primary partition marked as | ||
| bootable. The details and the steps required to set up the SD card | ||
| for each of the boot modes are elaborated in the following 2 sections | ||
| on SD card booting. For more information on "raw" mode and FAT mode, | ||
| please refer to the AM335s TRM Sections 26.1.7.5.5 and 26.1.7.5.6 | ||
| respectively. | ||
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| In order to boot uMon from an SD card using FAT mode, a GP Header must | ||
| be prepended to the uMon image. In the case of booting uMon using | ||
| "raw" mode, both a Configuration Header TOC Structure followed by a | ||
| GP Header must be prepended to the uMon image. | ||
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| The GP Header is 8 bytes long where the first 4 bytes specify the size | ||
| of the uMon image that will be transferred while the last 4 bytes | ||
| specify both the destination address where the uMon image will be | ||
| transferred to and the entry point. | ||
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| For information on the layout of the Configuration Header TOC Structure | ||
| required for "raw" mode booting, please refer to the AM335x TRM | ||
| Section 26.1.7.5.5.1. | ||
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| One thing worth mentioning is that the Beaglebone Black is connected to | ||
| the SD card using MMC0 and as a result the size of the SD card must not | ||
| be greater than 4GB. This is indicated in the AM335x TRM Section | ||
| 26.1.7.5.2. | ||
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| In order to configure the Beaglebone Black to boot from an SD card, | ||
| a uSD must be inserted and the boot switch held down while the board | ||
| is powered up. Once the board is powered on, the boot switch can | ||
| be released. If the attempt to boot from the uSD fails, the | ||
| Beaglebone Black will fall back and attempt to boot using UART. | ||
| As a result, this will provide a way to indicate whether the boot | ||
| from SD succeeds or not. | ||
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| RAW MODE: | ||
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| In order to boot from an SD card using "raw" mode, the uMon image | ||
| must be prepended with a Configuration Header TOC Structure and a | ||
| GP Header. The GP Header is placed right after the Configuration | ||
| Header TOC Structure. | ||
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| With the proper headers prepended, the image is ready to be booted. | ||
| In order for the Beaglebone Black/AM335x to boot the image from an | ||
| SD card, the image must be placed at one of the offsets | ||
| 0x00000/0x20000/0x40000/0x60000. | ||
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| Assuming the SD card is /dev/sdc, to place the uMon image at the first | ||
| offset of the SD card | ||
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| # Get the size of the uMon image to transfer into the SD card | ||
| export UMON_IMG_SIZE=`wc --bytes <uMon image> | cut -f 1 -d ' '` | ||
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| # Transfer the uMon image at offset 0x00000 | ||
| dd if=<uMon image> bs=1 count=$UMON_IMG_SIZE of=/dev/sdc | ||
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| FAT MODE: | ||
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| In FAT Mode, an "MLO" file is searched for in the root directory of | ||
| a primary partition formatted as FAT12/FAT16 or FAT32 and marked | ||
| bootable. This "MLO" file must contain a GP Header followed by the | ||
| uMon image. When uMon is built, an "MLO" file is already created and | ||
| is located in ./build_BEAGLEBONEBLACK. | ||
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| The next sequence of steps detail how to prepare an SD card for | ||
| FAT Mode booting for the Beaglebone Black to boot from. | ||
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| Assuming that the SD card has not been formatted yet... | ||
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| The first step is to create a primary partition with the filesystem | ||
| type set to FAT32. This primary partition will be placed as an entry | ||
| in an MBR and will be located in the first sector of the SD card. | ||
| Fortunately, these intial steps are taken care of by the fdisk utility. | ||
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| To allocate a partition that will be formatted as FAT32 and to create | ||
| an entry for the partition in an MBR, | ||
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| fdisk <device> | ||
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| where device is the SD card. Suppose the SD card is registered | ||
| under /dev as "sdc", this would be | ||
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| fdisk /dev/sdc | ||
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| fdisk will then present a command-line dialog. | ||
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| From here, a new partition must be created using 'n'. This partition | ||
| must have a type of 0x0C for FAT32 which is set with 't' and with the | ||
| the number of sectors allocated to this partition to be set to at least | ||
| 100, which is enough to hold the size of the current uMon image and to | ||
| allow for future expansion. It is recommended that not all the sectors | ||
| of the SD card be allocated to the FAT32 primary partition in order to | ||
| provide room for the possibility of storing user data or perhaps | ||
| a kernel. | ||
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| Once that is done, the next step is to mark the primary partition as | ||
| bootable. This is done using the 'a' option. | ||
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| With all that in place, the partition can be verified before writing | ||
| it to the SD card with 'p'. Once the partition has been verified, | ||
| it can be written to the SD card using 'w'. | ||
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| After using fdisk to set up the partition, this should present the | ||
| newly created partition as /dev/sdc1. | ||
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| The next step is to format this partition as FAT32: | ||
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| mkfs.fat -f 2 -F 32 -M 0xF8 -R 32 -s 64 -S 512 /dev/sdc1 | ||
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| The final step is to place the "MLO" file in the root directory | ||
| of the FAT32 primary partition. | ||
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| cd ~ | ||
| mkdir mnt | ||
| mount /dev/sdc1 mnt | ||
| cp <path_to_umon>/ports/beagleboneblack/build_BEAGLEBONEBLACK/MLO mnt | ||
| umount mnt | ||
| rmdir mnt | ||
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| The SD card is now ready. | ||
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| ----------------------------------------------------------------------- | ||
| UART: | ||
| ----------------------------------------------------------------------- | ||
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| In order to boot from UART, a 3.3V USB-to-Serial cable is required, | ||
| e.g. the FTDI USB TTL Serial cable is a possible option. | ||
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| The last requirement is to have a terminal emulator | ||
| (e.g. minicom/picocom/etc.) set up to perform XMODEM transfers using | ||
| 1K packets and 16-bit CRC. | ||
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| To initiate the UART booting procedure on the Beaglebone Black, ensure | ||
| that there is no uSD card inserted and then hold the boot switch down | ||
| while powering up the board. Once the board is powered on, the boot | ||
| switch can be released. | ||
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| If a terminal emulator is set up already and connected to the serial | ||
| port of the Beaglebone Black, the character 'C' will be outputted | ||
| continuously. This indicates that the UART booting procedure has | ||
| initiated and is waiting for an image to be transferred via UART. | ||
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| From here, the uMon image can now be transferred using the terminal | ||
| emulator. | ||
| ======================================================================= |