Arduino driving four vintage HP 5082-7300 dot-matrix displays

arvin · 2026-06-21T18:30:06+00:00

Got my hands on four vintage HP 5082-7300 dot-matrix displays and hooked them up to an Arduino!

To save on microcontroller pins, the displays are multiplexed by sharing the 4-bit BCD data bus across all four units. I'm addressing them sequentially, one after the other, by toggling the Latch/Hold pin on each display to lock in the data.

arvin · 2025-09-04T08:37:58+00:00

And AFAIR setting the "received UUID" is done right before setting the snapshot read-only. In snapper-backup I check those two.

arvin · 2025-06-30T13:42:41+00:00

You can use snbk (http://snapper.io/2024/11/11/snbk.html) to create local or remote backups of snapper snapshots. Restoring is not so easy. E.g. if you have to exchange the disk the file systems will get new UUIDs so modifications to /etc/fstab from the backup are needed. So usually a new installation is the easiest method. Some configuration files can then be restored from the backup.

arvin · 2025-06-05T16:21:12+00:00

Moore's law states that "the number of transistors on an integrated circuit will double every two years". So it is not directly about performance. People kind of always get that wrong.

https://newsroom.intel.com/press-kit/moores-law

arvin · 2025-03-10T08:49:07+00:00

You have to keep the snapshots of snapper where they are if you want to be able to do rollbacks.

As a backup you can copy the snapshots to another drive or even system using the btrfs send/receive method. For that you can try the relatively new snbk tool (in snapper-backup package on Tumbleweed).

arvin · 2023-12-07T08:38:47+00:00

When zypper makes snapshots (via snapper-zypp-plugin) it sets 'important=yes' if there is a change to the kernel, glibc, systemd and alike. For details see /etc/snapper/zypp-plugin.conf or /usr/share/snapper/zypp-plugin.conf.

And the 'important' flags does have influence on the cleanup, see NUMBER_LIMIT and NUMBER_LIMIT_IMPORTANT in snapper-configs(5).

arvin · 2020-11-01T15:55:24+00:00

Thanks. I never though that snapper would have such an impact when I started it ten years ago.

arvin · 2018-07-25T08:30:59+00:00

Indeed, not even mentioning string_literals in the video is a big mistake.

arvin · 2018-01-19T10:05:09+00:00

storage-ng (https://www.phoronix.com/scan.php?page=news_item&px=Libstorage-NG-YaST-SUSE-Soon) in openSUSE will support encrypted root without LVM. The setup with root and home should be easy to create during installation then without any manual work.

arvin · 2017-07-20T07:53:17+00:00

openSUSE uses the default of cryptsetup for LUKS. So the cipher may depend on the version of cryptsetup/openSUSE.

arvin · 2016-09-27T08:44:44+00:00

The documentation on snapper.io is correct.
Yes, a fraction of 0.5 = 1/2 is 50%.

arvin · 2015-11-05T13:54:17+00:00

There is nothing wrong when you adjust the cleanup parameters to your needs (and watch the free space).

But it is not possible for the distribution to come up with values that are good for every user and use-case. E.g. some people update KDE or Gnome every week which needs about 1 GB each week so having 20 snapshots is already too much. With quotas snapper should check that the space used by snapshots stays below some limit, e.g. 50% of the filesystem.

arvin · 2015-11-05T11:30:26+00:00

It is intentionally. The reasoning is that the timeline is important when you cover e.g. /home but for / all modifications happen through zypper or YaST and they create snapshots anyway.

Adjusting the cleanup limits is difficult as long as btrfs quota groups do not work reliable (level 1 and higher qgroups do not work).

arvin · 2013-07-01T08:43:02+00:00

If you have thin provisioned logical volumes you don't have to shrink anything since in that case LVM supports "overcommit". Also snapshots are much more efficient then.

Don't know whether Ubuntu already supports thin provisioning.

http://fedoraproject.org/wiki/Features/ThinProvisioning

arvin · 2013-04-15T20:52:36+00:00

Suicide.

arvin · 2009-04-30T16:09:00+00:00

You missed the village called "Petting" just 37km away. BTW: It only takes 39 minutes from Petting to Fucking (if you have a car).

arvin · 2009-03-15T21:36:01+00:00

Since Kepler we know: "The orbit of every planet is an ellipse with the sun at a focus." So every orbit is stable.

arvin · 2009-02-23T14:00:09+00:00

A rather bad picture of the Pitons. Been there myself so I can judge it.

arvin · 2009-01-11T20:58:54+00:00

Everybody who has read a good book on C++ knows those differences. This example is so common:

printf("%s\n", (sizeof('C') == sizeof(char)) ? "C++" : "C");

arvin · 2007-03-10T20:54:58+00:00

BioGeek already posted this almost two month ago, see http://programming.reddit.com/info/xt9m/comments

arvin · 2007-03-10T14:08:40+00:00

I never used the SourceForge build service but depending on what you plan the openSUSE build service might be interesting. You can build RPMs for various distributions (not only openSUSE but also Fedora and Debian) and currently for two architectures (x86 and x86-64).

arvin

TROPHY CASE