Similar to this, among custom keyboard builders it's quite popular to have USB handled connected via TRRS headphone jacks between split keyboard halves [0] [1] and sometimes even the keyboard -> PC Connection being a custom TRRS -> USB cable or other exotic variations. [2]
While it is quite popular, TRRS is one of the worst connectors possible for a power rail (eg usb VBUS) because it all but guarantees that VBUS will be shorted to ground if you ever accidentally hot-plug it.
VCC is on the sleeve, last to enter the jack, GND is a ring deeper inside the jack. It's not clear to me how VCC would ever get grounded unless you pushed the connector in too far somehow.
There is a note about a diode across VCC and GND — perhaps that is to prevent this kind of short?
Think about unplugging from the side thats _delivering_ the power. As you pull it out, the GND (which is further in and needs to travel out as it's unplugged) will contact the live VCC.
Even from the power consumer side, there is a chance that a single female side contact (eg VCC) may touch two adjacent TRRS sections as the plug is being removed.
No, that's not how that works. If tip is ground and ring is Vcc, there is no possible way to create a dangerous short.
So lets imagine what happens to the host port when you unplug a live device. Vcc breaks first, and all other pins shift. D+ and D- are safe to short together or to ground (and I'm pretty sure safe to short to Vcc) so they don't matter much. The shield is physically out of the socket. As the connectors move, you get connections that put Vcc on the device's Data pins, through the device ground to host Data pins. This is equivalent to a large resistor between host Vcc and data pins, which is safe.
As the connector is removed, the device's ground contacts host's Vcc. Nothing happens because all the other pins are physically outside of the socket. There is no circuit, no path for the current to go. The only way it could be a problem is if the device had some external ground connection. That would create a direct short between the host's Vcc and ground.
But (correctly implemented) USB ports can safely tolerate a short from Vcc to ground. If not, it's not complicated or expensive to build protection into the device.
Even if all of the above weren't true, it's still not complicated or expensive to design a port which is tolerant to any kind of short on any pins.
What you're arguing is both not possible and wouldn't be a problem even if it were.
There are ways to handle it. For example, before it is firmly plugged you can just sense what is happening -- us minimum voltage and high impedance to prevent sparking and to get information about the state of the mating.
You only turn on actual power when it is firmly connected and you turn it off immediately when there is any signal that it might be disconnecting.
The trick is doing so in a way which requires basically zero hardware. DIY ergo keyboards are built around a controller like the Pro Micro - which can't do this out-of-the-box.
Having to add a bunch of components to implement such a feature isn't really worth it when switching to USB-C also solves the problem, at basically zero cost and effort. It's not spec-compliant of course, but who cares with DIY?
Most split keyboards these days have a microcontroller in each half. IO expanders like the MCP23017/MCP23018 are fairly expensive, quite slow when used with microcontrollers like the ever-popular Pro Micro's ATmega32u4, and they really limit your hardware options on the secondary side.
It usually makes more sense to just stick a Pro Micro on each side, and have them talk serial over TRRS. As a bonus, you can connect it to your PC from either half.
Recently I found myself in the market for a custom keyboard, to my great surprise. Custom as not as DIY but as something different than $10 OTC or even $100 Logitech.
After the hours of watching pics I decided to just see it with my own hands and went to a shop which specialize on them.
And there I confirmed the feeling what I had before - 99% of these keyboards, despite quite advanced tech gone into them on all layers, are not usable, because they are made to stroke the ego of the owner but not for the actual work. This is especially evident by the crammed right cluster which makes typing brackets, curlies and quotes quite a pain, because the Shift key is gutted and nowhere under the right pinky.
Using something else than microUSB or Type-C (for the PC connector) is just a cherry on top.
They use USB-C to the host, the TRRS simply communicates the two halves of the split between each other. You don't plug the keyboard into the 3.5mm jack on your PC!
You could just get a custom keyboard that is comfortable for you. Key mapping is generally an independent step. Most of these keyboards are completely programmable with custom keymaps and layers. Many come with blank keycap options, you can also rearrange a regular keycap set.
You can't do what OP is looking for without a custom PCB. The switches and caps and mappings might be customizable but their physical position and size on the board isn't.
Despite pushing the envelope in many ways, custom keyboards can also be strangely traditionalist at the same time. Making a PCB is a risky venture and most manufacturers don't want to risk it.
A huge amount of models still use a huge 7u or larger space bar for example when something as small as 4u would suffice, and leave room for much more ergonomic placement of modifiers. (or other improvements like extra keys, keyed gaps etc.)
Yes, most keyboards still have the traditional layout. But I believe many options fit what OP needs. A split keyboard such as Ergodox EZ allows access to the maximum amount of keys possible without moving your hand. You can then customize the mapping to properly distribute commonly used keys.
Ergodox EZ is ortholinear. Ortholinears by their nature tend to not have spacing issues but they require (extensive) retraining.
There's a very good chance that the above poster was looking at staggered layouts if it's their first foray into custom keyboards, and not even considering orthos.
I have an iPod shuffle first generation and the form factor is nearly perfect. It has a standard 3.5mm headphone jack on one end and a USB-A connector on the other end. Unfortunately, the battery is dead and not very user serviceable. For something like working out or tuning out, it’s about as minimalist as is functional and if storage wasn’t an issue, could double as removable storage.
Heikki Ylinen's iPod Shuffle Manager, for the unaware, is a portable 12k app that sits on the root of an iPod shuffle. When you launch it, it scans the entire stick for MP3 files, then builds a compatible iPod shuffle database and shoves it where it needs to go so the Shuffle just acts like a dumb MP3 player without iTunes.
It's a bit more bulky (classic iPod sized), but check out Tangara: <https://www.crowdsupply.com/cool-tech-zone/tangara>. Stock, easily replaceable parts, USB-C+3.5mm+BT, SDXC slot with 2TB limit, standard lipo battery, OSS & hackable firmware that's difficult to brick, basically every bit of it is designed to last decades.
The build quality looks really cheap. Since it's only a kickstarter, I assume the 3D printed case is only for prototyping, but it doesn't look like it would last very long. For $250 I would expect a much better case than that
I think it could be a very good target for a Rockbox port, however they very specifically emphasize Lua and hackability among their goals (check out the UI code samples); they're also developing the hardware+software platforms in tandem, I'm not even sure if Rockbox supports Wifi or BT.
You could take a look at the Rockbox supported device list[1]. Depending on the size requirements and the budget you could go for a Sansa Clip+.
I personally prefer the iPod Nano 7th gen, which is great in terms of usability, has bluetooth 4.0 and is also very small size. Repair is a nightmare though and finding an affordable but still working device is not that easy.
If smallest size is not a requirement, you could go for the HiBy M300 - a pretty new Android 13 device supporting most Apps, 2TB of microSD Storage, having control buttons and also cable headphone remote support (OMTP, not CTIA), but still not that big.
Maybe a modified Apple iPod Classic 2009 with an iFlash Quad and 2000mah battery also fits your needs. It's way bigger than a shuffle, but it's at least maintainable (battery and storage replacement).
Absolutely. The iPod Mini is a usable device that can be modded. The only thing I'm missing on these "older" models (not that iPod Classic 2009 or iPod Nano 7g 2012 are young) is the earphone remote control (e.g. of the cable EarPods).
Apple did a really great job on remote controlling the devices with "tap"-Codes (tap, double tap, triple tap). The iPod Classic 2009 for example does not support the codes for fast forward / rewind (tap+tap_hold=ff, tap,tap,tap_hold=r). That's something I regularly use for audiobooks, so I'm tied to the iPod Nano 7g (the 6g would also work, but I prefer the larger display for navigating chapters).
There are android devices supporting these tap codes partially, but not as good / reliable as the iPod Nano 7g. Android also is using OMTP while Apple is using CTIA, so Apple headphones won't work on android and vice versa. CTIA=>OMTP Adapters (from amazon) just switch the pinout, which does not work, because Apple uses different Resistance on the Pinout.
I also "modded" one of my iPod Nano 7g by partially milling out the aluminium backplate and soldering in an iPod Mini battery (600mah), so that I got nearly 3 times the battery life of a factory iPod Nano as well as an easy to replace battery without opening the device (which is way to hard). The bigger iPod Mini battery does not fit without a silicone bumper, but since I already used one, it was perfectly fine. Changing the battery still requires soldering, but at least not fiddling with the very fragile display removal procedure.
However, currently I did not find a better device for my use case than the iPod Nano 7g. And everything is better with bluetooth... although I don't use it :-)
get one that has aftermarket firmware support, the ones i've played with have very specific conditions for folder/file naming and structure and format. The last one I tinkered with didn't support ogg vorbis out of the box, which is a somewhat niche format admittedly -- but support for it is fairly widespread elsewhere so I just sort of took it for granted that it'd deal with it fine.
I found a cheap MP3 player a couple years ago for like $30 on Amazon. It looks like a 2nd gen iPod nano and takes an SD card slot. I have literally never needed to charge it, the specs are so tiny.
Ah yes, the pack-of-gum sized model with the "do not eat iPod shuffle" warning.
I had one of the USB-via-TRRS models that this post is about and really liked it for running. Had a built-in clip so you could attach it to your waistband.
One problem with using TRRS for USB is that Vbus can be short-circuited while plugging and unplugging; the clones of the 2nd generation Shuffle tended to use a regular mini-USB instead, which offers the advantage that it can be charged while listening: http://tarkus-notes.com/en/chinese-mp3-player-ipod-shuffle-c...
The first version of USB should have used TRRS connectors. Then wouldn't have people complaining about inserting the cable incorrectly or having to deal with the plethora of USB connectors.
The problem with TRRS is that the different pins get shorted together when plugging in or disconnecting it. This means devices now have to handle a dead short as part of regular operations, which seriously complicates the interface.
The hobbyist ergonomic keyboard community has used TRRS for the link between the left and right half of the keyboard for a while now, and it routinely causes issue due to people accidentally unplugging it while powered - which fries their keyboard.
I totally expect the 3.5mm Toslink plug to come back once we inevitable switch over to fiber, though!
But phone connectors have built-in switches, so I would think there must be some configuration to route the powered lines through the switches so that the power is only connected until the plug is fully inserted, I think. For instance, if insertion of the tip control a double-pole double-throw switch, then one of those could route the ground pin and one could route the power pin, such that those power lines are only routed once full insertion has been made.
> The hobbyist ergonomic keyboard community has used TRRS for the link between the left and right half of the keyboard for a while now, and it routinely causes issue due to people accidentally unplugging it while powered - which fries their keyboard.
I believe that someone has had this problem, but I cannot replicate it. I unplug the right hand of my Iris all the time like a jackass and so far no ill effects. IDGI.
It depends a lot on the exact pinout used by the individual keyboard, and which side you disconnect first. I'm active in a community dedicated to keyboards like these, and I think we see someone with a dead keeb due to it once a week or so.
There are a few big reasons to prefer TOSLINK over other digital interfaces:
Cost: TOSLINK can be implemented with two plastic connectors (one an LED, one a photodiode). After that, you're in a 3.3V domain. Other interfaces require transformers and other analog electronics to go from the signalling domain to one that is useful in a digital system.
Noise/electrical performance: Using an optical interface means the systems are fully electrically isolated, with no risk of ground loops or noise coupling. There is also no risk of radiated emissions.
Cabling convenience: TOSLINK supports a very long, thin, cable that can be checked for functionality at a glance (look at the receiver end: is there light?). Any comparable electrical interface is going to be at least 3 conductors and require a multimeter to check for breaks.
Lastly, the reason to prefer digital is that every A/D-D/A step adds noise, distortion, and latency. The general desire is to convert to analog as late in the chain as possible to avoid that.
Not necessarily. You could design the plug like "copper tip, plastic ring, copper sleeve". With the right dimensions the contacts aren't shorted together during insertion.
Alternatively, use a ring which is segmented in 120 degree pieces, and place two contacts 180 degree apart in the socket: any two ring segments might be shorted, but never all three - and there will always be at least two segments with a connection. Use a bridge rectifier to get a fixed polarity out of it.
Those problems weren’t really problems at the beginning, though. USB 1/1.1 only had A for host connectors, and B for peripheral connectors. And people didn’t spend much time hot swapping devices back in the those days either. Most peripherals sat on a desk and didn’t move much. The meme about always having to rotate USB came about more so in the days USB flash drives. And in the early days of USB flash drives the issue wasn’t plugging it in, it was that windows didn’t include mass storage device drivers!
I think TRRS USB would have resulted in people confusing them with the much more common audio connectors and confusing host and peripheral. That could have killed USB from the start.
That doesn't matter though. When you design a plug you take UK into account and USB-A is about as bad as it gets. I've never plugged in the connector to my headphones the wrong way around because there isn't a wrong way. And that's a design that goes back to ... 1877!
USB wasn’t a reinvention of an audio connector. It was a replacement for a dozen if not more D Sub and DIN connectors that other serial connections used. Thus the ‘U’.
Nonetheless as TFA indicates, the iPod Shuffle 2G+ magically crammed USB into the TRRS audio connector in a way that was reliable enough to work in a mass-market product. As others have noted the design is potentially risky since power and ground are right next to each other, etc.
> As others have noted the design is potentially risky since power and ground are right next to each other, etc.
That's $0.30 worth of hardware to deal with though. Of course in mass market products such amounts really matter but I feel that the convenience and reliability factor as well as consumer centric thinking should allow for that kind of expense.
I have a couple of USB A cables that work in either orientation - seems like a design that should have been adopted more widely, though they seem a bit easier to damage if you step on them.
They work fine and still have a metal sleeve, but as I noted they are slightly flimsier because of their design which looks like [|] with a thin bit in the middle.
You can search for "reversible USB A cable" - there are lots of them available for sale.
I assume the "USB Trident" logo is imprinted on both sides since you can plug it in either way. ;-)
power through a copper on copper connection will oxidize over time, which will then result in the the 'crackliness' you get in analog audio, crackliness applied to a high speed data signal = fatal flaw.
It works as a hobbyist solution, but it's a long term disaster.
One of these is still currently in use in my household -- we've got a kid that likes music but is not yet old enough for any "smart device". Super portable, clips to the very over-ear headphones that it's plugged into!
I was never sure if I'd need to recreate make some cable for it, or if it's battery would fail first.
I've seriously considered replacing the cable on a pair of headphones[1] with a flush 3.5 mm TRS plug so I can directly attach a shuffle gen 4 — no clip required! — then putting a TRS plug on the original cable so I can still use the headphones with other devices.
Despite a long history of avoidance, it appears I will finally have to learn about the Apple iPod/iTouch as part of what might well be computer archaeology at this point.
But I suppose, looking back, much of my computing history is doing weird and unlikely stuff for a strange payoff, so at least I am consistent.
My hope is that I can avoid iTunes, which, on Windows, has a reputation for trashing collections willy-nilly.
Are there any pure - no OS or screen - mp3 players around that accept bluetooth?
I'm running my little sony walkman mp3 usb stick into the ground, but it only accepts wired in ear phones, and they tend to break a lot (and are now starting to confuse young salesman in electronics shops).
I am on my third Mighty due to faults. The first one was an early model which had an unpatchable firmware issue that bricked it. They sent me a replacement, for free. One the second one, the cable (and jack port) keeps corroding, meaning I can no longer charge it.
I have emailed customer support 3 times with no reply, tried Twitter and literally cannot get a response from them at all. Really really disappointing as I love(d) the product and what the company was trying to create.
You're probably thinking of the 3rd gen version, which, had exactly zero buttons (the only way to control it was to press the button on the included Apple earbuds): https://apple-history.com/ipod_shuffle_3g
The same measurement of resistance between the innermost two contacts is now a standard for Android in-line headset controls, although Apple's implementation used 0, 4.7k, and 10k ohms instead of Android's much lower (<1k) values.
OP here, you're getting down-voted, but you are actually correct. Seeing that meme reminded me I once owned a cable like that, and got me wondering how it worked.
a picture of a short cord with a USB A on one end and a 1/8" headphone jack on the other, both ends plugged into the same laptop computer (one end in the USB jack, one in the headphone jack). Supposed to be a "wtf" kind of thing.
This 1/8" TRRS connector is about 5 billion times better than any of the Mini-B, Micro-B, USB-C stuff that came out later.
I break a USB cable every week just because it gets wedged between 2 standing desks, stuck in office chair, gets slammed in car door, bent by thigh while in pocket connected to device, etc.
The people who designed USB Micro-B and USB-C are probably people who sit in an office all day and never bike, ski, etc. They don't realize that "consumer grade" stuff needs to be 10X stronger than military grade. Consumers connect devices together, stuff everything in pocket with wires connected and go skiing. Military people just sit in an armchair behind bulletproof glass and fire.
Never had a 1/8" headphone jack break that way, I've dropped bricks on those things, stomped over them, biked over them, had them sucked up by vacuum cleaners and vacuum robots, chewed by pets, they've been largely fine. A 1/4" headphone jack once got wedged between two standing desks and it was strong enough that the whole desk lifted off and the cable was intact, the jack barrel alone supporting the entire 100 kg of desk with everything on it. Cable still functions perfectly. REAL consumer grade stuff.
[0] https://keeb.io/products/trrs-cable
[1] https://docs.splitkb.com/hc/en-us/articles/360010443660-Kyri...
[2] https://www.kingcables.org/products/custom-straight-usb-cabl...