I didn’t get out much in Munich as it was an intense week of work, but one morning I did take a walk in the park that borders the Eisbach river. It was cold, rainy, and quite enjoyable.
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Munich 2023
Author: Tanner
I’m starting to dust off some seasonal projects and realized I hadn’t made this simple tool public which others may find handy. With projects like the NeoPixel Tree it can be much quicker to code visual sequences locally instead of waiting for new firmware to upload to the MCU every time you want to tweak something.
The tool just wraps around the Adafruit GFX Graphics Library and instead of outputting to physical pixels it runs through SDL2. It’s somewhat similar to what I did in swift-gfx-wrapper but keeps it all in C.
GitHub repo: https://github.com/twstokes/gfx-proto
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Amsterdam 2023
Amsterdam was so nice! Great food, going to Tony’s Chocolonely, meeting friendly cats, avoiding bicycles, a ride in the canal, and visiting the Anne Frank memorial just to name a few highlights.
Maybe if I share videos of half-finished projects it’ll motivate me to finish them!
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64×64 LED Matrix + Doom
From the weekend hacks department: I now have DOOM running on my 64×64 matrix!
- A Raspberry Pi 2B drives the 64×64 3mm pitch LED matrix via the Matrix Bonnet.
- I’m using SDL2 to handle scaling the original resolution of 320×200 down to 64×40 as well as the game ticks, user input, and sound.
- It was mainly an exercise in Makefiles and linking C libraries – the hard parts were done in the libraries. 🙌 Generic Doom / Rpi RGB LED Matrix
- The matrix is covered with an acrylic panel that smooths out the LEDs and makes it pleasant to look at.
- The flickering effect isn’t seen in real life, it’s just how the camera captured it.
GitHub repo: https://github.com/twstokes/doom-matrix
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OpenBSD + iMac G4
Fun fact: You can put the latest version of OpenBSD on a PPC 32-bit processor like the G4. Fun to dual boot with Mac OS 9 if you want a modern, secure computer!
Some notes
The OpenBSD docs are really good and thorough. Open Firmware needs some tweaking if you want to boot directly into OpenBSD, so this is what I did after booting into it with command+option+o+f:
setenv auto-boot? True
setenv boot-device hd:,ofwboot
reset-allI failed to get a USB install working
Initially I didn’t want to mess with the internal drive of the iMac since I had both Mac OS 9 and Mac OS X installed, so I tried to install to a USB drive. Although the installation succeeded (albeit extremely slowly due to USB 1.1), the boot into the system failed due to the following error:
panic: rootfilesystem has size 0
Looking at the trace of the kernel boot process it was evident why: Even though we installed the OS to sd0 (the mounted USB device), the kernel kept trying to mount wd0 which is the internal IDE drive.
I tried what I knew:
- Tweaking the
boot-devicevariable in Open Firmware - Using a different USB slot
- Booting into the recovery kernel (
bsd.rd) and mounting the USB to see if I could tweakfstab
Supposedly if we get to the boot prompt we can pass a -a flag for the root device (docs), but I couldn’t figure out how to get there.
Ultimately I decided to install OpenBSD to the main internal drive for now. If I get a hankering for Mac OS 9 I still have the trusty Power Mac G4.
The best setup will eventually be a dual or triple-boot. Trying to make the super-slow USB drive work is probably a terrible idea unless we plan to run it in a ramdisk mode the entire time.
The graphics driver kinda works
As you can see from the glxgears output above graphics are not accelerated. I’ve mostly played with the machine over SSH in a headless state so this hasn’t bothered me too much. I did glance at dmesg and saw that the expected driver, nv, was loaded and detected the card so I’m not totally sure what’s happening. I’m having flashbacks of when I used to spend hours tweaking xorg.conf and that may be on the horizon again.
If just running the console we still want the screen to sleep and I found I needed to make a couple tweaks for that to work.
First I needed to shut down X Windows:
rcctl stop xenodm
Then I needed to disable output activity from waking the screen:
display.outact=off
After that the screen would shut off after however many milliseconds were set for display.screen_off.
Copying over /etc/examples/wsconsctl.conf to /etc/ is a great starter config.
Turn-key graphics support depends on the model
If you’re running a G4 iMac 15″ that’s less than 1GHz, you have the GeForce2 MX which doesn’t have support out of the box via the nouveau driver. This means an unaccelerated graphics environment, low framerates, and sometimes a console that has inverted colors making it really hard to use.
The GeForce4 MX integrated on the 1GHz 15″ model and most of the 17″ iMacs is supported.
glxgears at a blazing 12FPS.Oh yeah, it runs DOOM
(Very poorly, presumably until the graphics driver is tweaked)
Running Chocolate Doom was painful. Even the setup utility had a good second or so input lag!
I first want to acknowledge that I did the thing that I try to never do: I showed off a snazzy project, left some hints here and there of how it worked, said I would follow up with full details… and never did. That’s lame.
I’ve had multiple people reach out for more info and I’m glad they did, since that’s pushed me to finally get some repos public and this belated follow-up written. Apologies!
To jump straight to it, I’ve published these two repos:
Hardware
Let’s first go over the hardware involved. The most important piece, of course, is the Alfa-Zeta XY5.
In my case, the 14×28 board was made up of two 7×28 panels connected together via RJ-11.
The panels are pricey, but they can be thought of as “hardware easy-mode”. Alfa-Zeta has done the hard job building the controller that drives the hardware and all we have to do is supply power and an RS-485 signal that abides by their protocol.
If you purchase a panel from them there are two important documents to request:
- The main manual that describes the specs, features, and things like the DIP switch settings.
- The protocol for sending commands to the controllers (which is really simple).
These can easily found by searching around, but if you own a panel the company should supply them. Most of the protocol can be deduced by looking at open source code.
Components
- Alfa-Zeta XY5 – 14×28 Flip Dot display
- NodeMCU ESP8266 – MCU
- 3.3v RS-485 to TTL – Allows the MCU to communicate over RS-485
- ALITOVE AC 100-240V to DC 24V 5A Power Supply – Required to power the panels
- BINZET DC 12V 24V to 5V 5A – Optional, used to step down power to the MCU so we have one power source
The 24V -> 5V converter isn’t necessary if you supply power to the MCU independently, say through a USB power adapter.
Connection overview
- 24V DC goes to both panels
- 24V DC goes to the step-down converter, 5V DC goes to the 5V input of the NodeMCU
- NodeMCU is wired to the RS-485 to TTL converter
VCC -> 3.3vGnd -> GndDE -> 3.3v pulled high because we're always transmittingRE -> 3.3v pulled high because we're always transmittingDI -> TX[x] x being 0 or higher depending on boardRO -> RX[x] most boards only have the main serial IO, but boards like the Mega have multiple
- RS-485 -> Only one panel controller – not both
An Arduino Mega is driving the board in this photo.
Software
The MCU
See https://github.com/twstokes/flipdots for the code that runs on the MCU.
At the moment there isn’t much to it – you can either compile the firmware to run in a mode that writes data from UDP packets to the board, or you can draw “locally” using Adafruit GFX methods.
See the README in the repo above for more details.
iOS / iPadOS / macOS
See https://github.com/twstokes/flipdots-ios for the code that runs on these devices.
Semi-interestingly I utilized Adafruit GFX again, this time via swift-gfx-wrapper to draw to the board over UDP. It’s hacky and experimental, but that’s part of the fun.
See the README in the repo above for more details.
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Controlling monitor inputs with DDC
I’m really happy that most modern monitors support DDC so that we can programmatically change settings rather than go through clunky OSDs.
The problem
At my desk I have my Mac Studio and my latest gaming PC and they both share a triple monitor setup. When I want to switch the monitors between the two, I either need to:
- Turn on auto-switching mode
- Manually change the input x 3
Auto-switching kinda worked, but has quirks I can’t live with. One is when I’m playing a game on the PC and the Mac wakes up for whatever reason, the PC receives a signal that hardware has been connected or disconnected and the screen freezes. It seems like a firmware bug to me – if an input is being actively used the others should be ignored.
The manual route is pretty bad as well. The M32U‘s input switchers are on the back of the monitor, which is pretty much the worst spot possible. Only the far right monitor is slightly more convenient to access.
How DDC solves it
By using m1ddc on the Mac we can easily script a way to switch between the two machines. 🎉 This means I can create a keyboard shortcut to toggle the inputs, a physical button, or even run it from an external computer. Hooray!
Edit: Now with web appi-ness!
I threw together a quick Flask app that can be accessed from any device on my network to switch inputs. Neato!
Note: Once I connect the left monitor the same way I connect the other two, the transition should be more in sync. Currently it’s a little slower due to the HDMI connection.
I recently set up a ZFS mirror on my home server and found myself needing a way to be alerted if something went wrong. That same server runs Grafana and InfluxDB, and collects various metrics from my other machines (and itself) via Telegraf. Since I already have email alerts set up with that stack, it felt simplest to use it for this solution.
A really simple script
#!/bin/sh
# Compares the expected zpool status output with the actual status.
# Copy to a global location such as /usr/local/bin so it's accessible to Telegraf.
# Note: This can provide a false-postive if the output of the command changes, which is not guaranteed to be stable.
# Returns 0 for "false" (not healthy), returns 1 for "true" (healthy)
# Chose using integers over booleans due to how Grafana handles alerts.
OUTPUT="zfs_status,host=[HOSTNAME HERE] healthy="
if [ "$(zpool status -x)" != "all pools are healthy" ]; then
OUTPUT=${OUTPUT}"0i"
else
OUTPUT=${OUTPUT}"1i"
fi
echo $OUTPUTThere are similar scripts floating around on the Internet so I used those for inspiration. The only difference with mine is that it outputs the InfluxDB Line Protocol.
host= is just a convenient tag where you could put your box’s hostname (or call the hostname command and interpolate it).
Everything else should be explained by the script, including the possibility of false positives. Feel free to rename the zfs_status field to anything you wish. In my instance I use tws_zfs_status to differentiate custom fields I’ve created and possibly prevent namespace conflicts.
The Telegraf side
Telegraf has a super handy exec input where you can run arbitrary commands, so that’s what we use:
[[inputs.exec]]
commands = ["sh /usr/local/bin/zfs_check.sh"]
timeout = "5s"
data_format = "influx"When Telegraf collects data from its inputs it will write a one or a zero for its zfs_status field.
And finally, Grafana
The basic setup in Grafana is:
- Stat type
- Grab the last value
- Map 1 to “Healthy” / green, 0 to “Unhealthy” / red
- Set up an alert for when the value is less than 1
That’s basically it! It’s a really good idea to test it by temporarily tweaking the script to output a 0 and waiting for an email to arrive. 🙂