sorted by: new top controversial old
[-] ch00f@lemmy.world 4 points 4 days ago

We had one of these. It was terrible. Spring force was super weak and slow and there was no lever to manually lift the toast if it got stuck.

[-] ch00f@lemmy.world 5 points 5 days ago

I heard that part of the motivation behind games like Pokémon Go is that they can collect data on previously unrecorded pedestrian routes between major landmarks or points of interest.

So Google’s directions may be based on crowd sourced routes that have never been vetted as safe/legal for pedestrians and cyclists.

[-] ch00f@lemmy.world 51 points 1 week ago

MIT students call elaborate pranks “hacks.”

Source: class of 2011

[-] ch00f@lemmy.world 7 points 1 week ago

Maybe not relevant for this specific discussion, but a decent quantity of Americans are stuck with fucking Dollar General for their groceries and they sure as hell don’t deliver.

[-] ch00f@lemmy.world 0 points 1 week ago

The solar sail reflects light instead of absorbing it so you get to double dip on photon momentum.

And sure, you can steer with the laser I suppose, but with that kind of super weak deltaV, you’re not going to be exactly doing donuts in the solar system.

Even the massive solar sail only imparts a super small amount of force. It’s only useful because it does so for free over a long period of time with no air resistance.

You’d be better off using a conventional thruster to do whatever steering you needed to do before letting the sail take over. It’s not like you need to steer around any obstacles.

[-] ch00f@lemmy.world 10 points 1 week ago* (last edited 1 week ago)

MP3 players are commodities now. Anyone who just wants iPod functionality can get it cheap, and there are even upmarket options for audiophiles with support for things like low impedance headphones that the iPod never supported.

There’s just not enough room in the market for Apple to re-insert themselves.

Also, they’d never ship a product that couldn’t somehow use AppleMusic.

[-] ch00f@lemmy.world 6 points 1 week ago

Sure, but it would be less efficient than a sail, and since the incoming radiation would impart inertia on the solar panels, you would still be limited on where you could steer.

[-] ch00f@lemmy.world 4 points 1 week ago

Yeah, I’m working on that part. It’s just messy because a lot of portions of the code can’t be confined to functions. There’s a lot of GOTO equivalents.

[-] ch00f@lemmy.world 11 points 1 week ago

I ditched my smartphone spring of 2023. Still use it on WiFi at home, but every time I leave the house, I only carry a fliphone.

Every time a stranger asks me about it, they say something like “I wish I could ditch my smartphone.” Like I get it. It’s not easy. I can’t even go to a baseball game unless my wife has our tickets on her phone. Paying for parking sometimes requires an app.

Yet apparently everyone hates this thing that they are now required to carry around.

How did we get here?

57

I dumped the ROM out of a piece of retro-tech and have been working through the code in Ghidra. Unfortunately, I can’t exactly decompile it because I don’t think it was originally written in a higher level language.

For example, the stack is rarely used and most functions either deal entirely in global variables, or binary values are passed back using the carry or other low-level bits. Trying to turn it into C would just make spaghetti code with a different sauce.

So my current plan is to just comment every subroutine as best I can, but that still leaves a few massive lookup tables that should be dropped into a spreadsheet of some sort to add context. Not to mention schematics.

My question is what’s the best way to present all of this? I’d like to open-source the result, so a simple PDF is not ideal. I guess I should make a GitHub project? Are there any good examples or templates I can draw on?

[-] ch00f@lemmy.world 0 points 2 weeks ago

Famous for their pears

[-] ch00f@lemmy.world 1 points 2 weeks ago

I have a mini-split. There’s no ducting in the walls.

[-] ch00f@lemmy.world 1 points 2 weeks ago

(For the US market. They still make sedans for Europe)

437
submitted 2 months ago* (last edited 2 months ago) by ch00f@lemmy.world to c/programming@programming.dev

I originally told the story over on the other site, but I thought I’d share it here. With a bonus!

I was working on a hardware accessory for the OG iPad. The accessory connected to the iPad over USB and provided MIDI in/out and audio in/out appropriate for a musician trying to lay down some tracks in Garage Band.

It was a winner of a product because at its core, it was based on a USB product we had already been making for PCs for almost a decade. All we needed was a little microcontroller to put the iPad into USB host mode (this was in the 30-pin connector days), and then allow it to connect to what was basically a finished product.

This product was so old in fact that nobody knew how to compile the source code. When it came time to get it working, someone had to edit the binaries to change the USB descriptors to reflect the new product name and that it drew <10mA from the iPad's USB port (the original device was port-powered, but the iPad would get angry if you requested more than 10mA even if you were self-powered). This was especially silly because the original product had a 4-character name, but the new product had a 7-character name. We couldn't make room for the extra bytes, so we had to truncate the name to fit it into the binary without breaking anything.

Anyway, product ships and we notice a problem. Every once in a while, a MIDI message is missed. For those of you not familiar, MIDI is used to transmit musical notes that can be later turned into audio by whatever processor/voice you want. A typical message contains the note (A, B, F-sharp, etc), a velocity (how hard you hit the key), and whether it's a key on or key off. So pressing and releasing a piano key generate two separate messages.

Missing the occasional note message wouldn't typically be a big deal except for instrument voices with infinite sustain like a pipe organ. If you had the pipe organ voice selected when using our device, it's possible that it would receive a key on, but not a key off. This would result in the iPad assuming that you were holding the key down indefinitely.

There isn't an official spec for what to do if you receive another key-on of the same note without a key-off in between, but Apple handled this in the worst way possible. The iPad would only consider the key released if the number of key-ons and key-offs matched. So the only way to release this pipe organ key was to hope for it to skip a subsequent key-on message for the same key and then finally receive the key-off. The odds of this happening are approximately 0%, so most users had to resort to force quitting the app.

Rumors flooded the customer message boards about what could cause this behavior, maybe it was the new iOS update? Maybe you had to close all your other apps? There was a ton of hairbrained theories floating around, but nobody had any definitive explanation.

Well I was new to the company and fresh out of college, so I was tasked with figuring this one out.

First step was finding a way to generate the bug. I wrote a python script that would hammer scales into our product and just listened for a key to get stuck. I can still recall the cacophony of what amounted to an elephant on cocaine slamming on a keyboard for hours on end.

Eventually, I could reproduce the bug about every 10 minutes. One thing I noticed is that it only happened if multiple keys were pressed simultaneously. Pressing one key at a time would never produce the issue.

Using a fancy cable that is only available to Apple hardware developers, I was able to interrogate the USB traffic going between our product and the iPad. After a loooot of hunting (the USB debugger could only sample a small portion, so I had to hit the trigger right when I heard the stuck note), I was able to show that the offending note-off event was never making it to the iPad. So Apple was not to blame; our firmware was randomly not passing MIDI messages along.

Next step was getting the source to compile. I don't remember a lot of the details, but it depended on "hex3bin" which I assume was some neckbeard's version of hex2bin that was "better" for some reasons. I also ended up needing to find a Perl script that was buried deep in some university website. I assume that these tools were widely available when the firmware was written 7 years prior, but they took some digging. I still don't know anything about Perl, but I got it to run.

With firmware compiling, I was able to insert instructions to blink certain LEDs (the device had a few debug LEDs inside that weren't visible to the user) at certain points in the firmware. There was no live debugger available for the simple 8-bit processor on this thing, so that's all I had.

What it came down to was a timing issue. The processor needed to handle audio traffic as well as MIDI traffic. It would pause whatever it was doing while handling the audio packets. The MIDI traffic was buffered, so if a key-on or key-off came in while the audio was being handled, it would be addressed immediately after the audio was done.

But it was only single buffered. So if a second MIDI message came in while audio was being handled, the second note would overwrite the first, and that first note would be forever lost. There is a limit to how fast MIDI notes can come in over USB, and it was just barely faster than it took to process the audio. So if the first note came in just after the processor cut to handling audio, the next note could potentially come in just before the processor cut back.

Now for the solution. Knowing very little about USB audio processing, but having cut my teeth in college on 8-bit 8051 processors, I knew what kind of functions tended to be slow. I did a Ctrl+F for "%" and found a 16-bit modulo right in the audio processing code.

This 16-bit modulo was just a final check that the correct number of bytes or bits were being sent (expecting remainder zero), so the denominator was going to be the same every time. The way it was written, the compiler assumed that the denominator could be different every time, so in the background it included an entire function for handling 16-bit modulos on an 8-bit processor.

I googled "optimize modulo," and quickly learned that given a fixed denominator, any 16-bit modulo can be rewritten as three 8-bit modulos.

I tried implementing this single-line change, and the audio processor quickly dropped from 90us per packet to like 20us per packet. This 100% fixed the bug.

Unfortunately, there was no way to field-upgrade the firmware, so that was still a headache for customer service.

As to why this bug never showed up in the preceding 7 years that the USB version of the product was being sold, it was likely because most users only used the device as an audio recorder or MIDI recorder. With only MIDI enabled, no audio is processed, and the bug wouldn't happen. The iPad however enabled every feature all the time. So the bug was always there. It's just that nobody noticed it. Edit: also, many MIDI apps don't do what Apple does and require matching key on/key off events. So if a key gets stuck, pressing it again will unstick it.

So three months of listening to Satan banging his fists on a pipe organ lead to a single line change to fix a seven year old bug.

TL;DR: 16-bit modulo on an 8-bit processor is slow and caused packets to get dropped.

The bonus is at 4:40 in this video https://youtu.be/DBfojDxpZLY?si=oCUlFY0YrruiUeQq

594
64
submitted 3 months ago by ch00f@lemmy.world to c/pcmasterrace@lemmy.world

Let’s call it hybrid soldered memory

51

So my home office is in our basement while my wife’s is in a finished attic space. We have a mini split system, but it has to be all heat or all cooling, and many days it’s cold in my office, but hot in my wife’s office.

Thanks to a defunct chimney, I have a pretty decent path from the attic to the basement that could easily accommodate some kind of ducting.

I’d like to make a system that can push air from my office to hers or vice versa as needed. I think this would really help the house in general as cold air tends to pool in the basement.

I’ve seen plenty of ducting booster fans, but I’d like something with a speed (or at least direction) control accessible from the outside.

Does something like this exist? It would need to force air through maybe 30-40’ of ducting.

14
submitted 6 months ago by ch00f@lemmy.world to c/selfhosted@lemmy.world

Per my previous post, I’m working on updating my server that’s running a J3455 Celeron with 16gigs of ram.

Goals:

  • Support at least six hard drives (currently have six drives in software RAID 6). Can move 7th main drive to nvme.
  • Be faster at transcoding video. This is primarily so I can use PhotoPrism for video clips. Real-time transcoding 4K 80mbps video down to something streamabke would be nice. Despite getting QuickSync to work on the Celeron, I can’t pull more than 20fps unless I drop the output to like 640x480. Current build has no PCIe x16 slot.
  • Energy efficiency. Trying to avoid a dedicated video card.
  • Support more RAM. Currently maxed at 16gb.
  • Price: around $500
  • Server-grade hardware would be nice, but I want newer versions of quicksync and can’t afford newer server hardware. Motherboard choice is selected primarily because of chipset, number of SATA ports, and I found one open box.

https://pcpartpicker.com/list/JX2gHG

Hoping to move my main drive to the NVME and keep the other six drives as-is without needing a reinstall.

Thoughts?

32
submitted 6 months ago* (last edited 6 months ago) by ch00f@lemmy.world to c/selfhost@lemmy.ml

I've been running a headless Ubuntu server for about 10 years or so. At first, it was just a file/print server, so I bought a super low power motherboard/processor to cut down on the energy bill. It's a passively cooled Intel Celeron J3455 "maxed out" with 16BG of RAM.

Since then it's ballooned into a Plex/Shinobi/Photoprism/Samba/Frigate/MQTT/Matrix/Piwigo monster. It has six drives in RAID6 and a 7th for system storage (three of the drives are through a PCI card). I'm planning on moving my server closet, and I'll be upgrading the case into a rack-mount style case. While I'm at it, I figured I could upgrade the hardware as well. I was curious what I should look for in hardware.

I've built a number of gaming PCs in the past, but I've never looked at server hardware. What features should I look for? Also, is there anything specific (besides a general purpose video card) that I can buy to speed up video encoding? It'd be nice to be able to real-time transcode video with Plex.

29
submitted 7 months ago by ch00f@lemmy.world to c/linux@lemmy.ml

I'm trying to write a simple bash script that opens up GQRX, sends it some TCP commands, then closes it down.

Unfortunately, I've found that when I close the program like this, the next time it opens, it will pop up a window saying "crash detected" and ask me to review the configuration file. This prevents the app from loading unless someone is present to click the dialog box.

This error only seems to happen when I try to close the program using the bash script. Closing it by just clicking the X doesn't cause this problem next time it's launched.

I think I'm closing the app too aggressively which terminates it before it can wrap up its affairs, and it interprets this as a crash. What's the best way to close the app to keep this from happening?

I've tried:

  • pkill -3 gqrx
  • pkill -13 gqrx

But the problem persists. Is there an even softer way to close an application?

328
87

Do guns wear out? Do they end up in landfill? You always hear about guns being sold, but never about what happens to them at the end of their useful life.

18
submitted 11 months ago by ch00f@lemmy.world to c/asklemmy@lemmy.ml
1

Recently started using a LightPhone II when out of the house, and I found the article captured my current experience pretty well. It’s not so bad to be bored sometimes.

view more: next ›

ch00f

joined 1 year ago