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My Armv7h microcomputers

Backup a uSDHC disk

cd <to-where-you-want-BU-file>
sudo dd if=mmcblk0 of=<suitableName>.bin

Be careful with dd - a false move and you can delete your harddisk.

Prepare a boot uSDHC

(Note: uSDHC means MicroSDcard, High Capacity. These are used to carrye the Operating systems for microComputers. First thing to do is to erase anything that is on the card:
Make sure you know what the cards id is: fdisk -l the output should show your card - on my systems it shows as mmcblk0p1, where p1 is “partition 1”, and the actual device ID is mmcblk0 (no 'p1'), with the dd command we\address the device, not the partition. Make sure the partition is unmounted, Proceed as follows (everything after '#'are comments, don't type them in):

sudo umount /dev/mmcblk0p1   # unmount the card
dd if=/dev/zero of=/dev/mmcblk0 bs=1M count=4   #fill first 4Mb with zeros
fdisk /dev/mmcblk0  #create partition with defaults..
mkfs.ext4 /dev/mmcblk0p1 #format & mount ext4 file system (NB now addressing partition, not device)
mkdir root    # this is a mount point on your host computer
mount /dev/mmcblk0p1 root

We now have a folder on the uSDHC called root. What follows is how to install an Archlinuxarm img there. Briefly what's happening: Download and unpcak an appropriate disk image for your micro-computer. The img comes Zipped, we unzip it to the root folder on the uSDHC we just created. and then, in the resulting file system, there are a couple of files in the folder /root/boot/ which must be copied from there to the very start of the card, before the partition - a part of the card which is normally invisible, but makes the card bootable. So..

bsdtar -xpf -C root
# ( I think I actually used tar rather than bsdtar )
# Install the bootloader
dd if=/root/boot/SPL of=/dev/mmcblk0 bs=1K seek=1 # Now  addressing device!!
dd if=/root/boot/u-boot.img  of=/dev/mmcblk0 bs=1K seek=42
sync  #flush
umount root #unmount

Eject the card and try booting from it on your uCPU - all should be well!

Cloning a uSD

is is very simple. As ever, be carefu that you are addressin ghte correct device - a wrong move and you could wipe you system.
To make the clone to a file:

# From the folder where you wish the clone to reside:
cd /media/myUsbDrive
dd if=/dev/mmcblk0 of=myOsClone.bin

Simple as that, and just reverse the procedure to write it to a uSDHC: dd of=/dev/mmcblk0 if=myOsClone.bin

Cross-compiling to Armv7f

It is quite a convoluted journey cross-compiling, but ideally I would like to be able to do it.
However, not yet. The priority is to get Csound6 and Analogue Audio out on the Hummingboard.
I read that it is doable: and
Some (wrong looking) stuff here
Typically it uses the HDMI as audio output; but there are small modifications to audio_policy.conf to make it to use the analog audio in / out.

I posted on the solid-run forum:

armv7h/start.txt · Last modified: 2020/04/08 00:22 (external edit)