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I am in all probability going to disclose my age right here, and annoy a couple of readers by asking who else, apart from myself, remembers a however of a novelty media kind issue from some years in the past, known as HitClips?
Ooph. The parents on the Museum of Out of date Media actually appear to recollect. I did not assume they have been that unhealthy, however I used to be additionally someplace round 11 -12 years outdated, so my requirements could have been subjectively decrease on the time…
Yeah, okay, I keep in mind how terrible the ’00s have been now. ’90s with infusion of the good WWW. However, as a child, this form of novelty tech was actually one thing else!
Whereas nowadays we’re spoiled with streaming companies galore on our high-speed smartphones, we’re reminiscent of the times the place MP3 gamers have been nonetheless the de facto strategy to get your music on the transfer.
I may mow lawns all summer season, however an iPod was all the time out of my worth vary — Hit Clips have been a bit extra on the inexpensive, if terrible, facet of issues…
Mass-produced musical modules!
In a nutshell, the participant machine within the HitClip ecosystem was actually extra a battery pack, and a small, fundamental audio amplifier. That is it. No brains, no microcontroller, simply that.
That leads us to wanting on the HitClip modules themselves, the place the magic actually occurs.
Greater than only a mere blob of flash, the HitClip module comprises not solely the “reminiscence” required for a miniscule audio pattern, but in addition some type of ASIC that can toggle a couple of pins in response to the audio reminiscence, leading to a bitstream illustration of the audio knowledge, used to drive the amplifier contained with within the HitClip participant machine.
Now we have “reminiscence” in citation marks, as there’s a nice remark from ch00ftech, of their completely superior write-up on reverse engineering the media format, that mass manufacturing of those gadgets would doubtless see the audio knowledge etched straight into no matter wire-bonded ASIC machine lives beneath the black epoxy blob within the HitClip cartridge.
With the work from ch00ftech serving as a elegant place to begin into secrets and techniques in how the HitClips labored, we now flip our eyes to the work of Man Dupont, who teased us on Twitter along with his current efforts to retrofit his personal homebrew {hardware} right into a HitClips music module, with outcomes that far, far exceed not solely the capability, however the constancyof the unique kind issue!
A tiny, marvellous M0+ MCU
Whereas beginning out with concepts primarily based across the venerable and nonetheless very usable 8-bit ATtiny84 from Microchip, Dupont rapidly discovered himself working up towards the constraints imposed by the slower clock velocity and small quantities of RAM discovered within the ATtiny — when in comparison with a more moderen MCU such because the ATSAMD09C, once more, from Microchip, which sits in the identical footprint, utilizing the identical exterior elements, however sadly is not pin appropriate. So shut.
However for the sake of transforming a couple of pins within the netlist and monitoring, we might say that the improve to the SAM D09 is actually definitely worth the effort. The bounce in functionality from transferring on as much as a 32-bit Cortex-M0+ is one factor, however you greater than only a newer, extra succesful processor.
A number of very good issues to have embody the flexibility to put in writing on to the whole, unprotected handle house of the flash reminiscence of the machine, and certainly one of my favourite serving to fingers to have; DMA — which helps you to join peripherals to behave routinely, and a lotextra rapidly than counting on the host processor to step in and kind all of it out. With entry to just about all the chip internals, It is totally potential in some circumstances to interchange an a complete utility with nothing however DMA descriptors (the definitions for “what, the place and when” that DMA will use).
A system degree overview of the SAM D09
DMA helps you to set off/provoke reminiscence transfers from FLASH to most peripherals, and again once more, and even from peripheral to peripheral in some circumstances — very helpful for purposes with numerous knowledge (e.g. audio).
With a succesful MCU in hand, Dupont has just about all he must already to spit out the Sigma-Delta bitstream, for use to drive the H-bridge amplifier that will likely be sat contained in the participant machine.
Nonetheless, as beneficiant as 8KB of is for such a small MCU, there are extra enticing choices on the market for mass storage options, resembling the ever-present µSD playing cards that all of us have sat about.
It would not take a lot to set certainly one of these large capability reminiscence playing cards up as a SPI flash machine, because of some helpful abstraction libraries — on this case, the Petit FAT File System library, from the legendary elm-chan — that deal with all the file system and SPI transport heavy lifting.
This one is bound to be a success…
For those who pair up a uSD card with a the aforementioned SAM D09, nicely, you get a fairly pokey, postage-stamp sized audio participant — the right dimension for packing right into a HitClip of your individual curation!
Dupont’s re-imagined, homebrew HitClip {hardware}!
There is not way more to this module than meets the attention — the reminiscence card, MCU, and two different ICs, which we see detailed within the schematic beneath.
The PWM Router is value mapping out by way of perform, because it appears a bit odd if you have not gone and browse that reverse engineering writeup from ch00ftech we talked about earlier.
The unique HitClip {hardware} would straight drive the push-pull FET pair present in a D-Class amplifier, seen beneath in the midst of the diagram within the block marked “Switching controller and output stage.”
(📷: en.wikipedia.org/wiki/Class-D_amplifier)
It would be good to have the ability to do that with a single PWM channel, and that’s what the “PWM Router” block within the schematic does.
AKA, a SN74LVC1G139 2-Line-to-4-Line Decoder, we will have a look at the inner logic to map out what is going on on with the bitstream.
If we apply the circuit internet names to the inputs, and try the reality desk, it begins to turn into a bit clearer!
We will see that the incoming PWM sign is mapped to both the Y1 or Y3 output, and that the sign goes to be inverted with respect to the polarity of the incoming PWM.
I can hear some individuals saying "okay, cool, however why not simply do it with the actually succesful MCU already right here?"…
Generally a {hardware} resolution is simpler than tying up two PWM timer outputs, and even simpler than attempting to de-interlace a bitstream in reminiscence to 2 totally different peripherals…
OpenSCAD — the software you did not know you really liked.
Not content material with cramming his new {hardware} into the constraints of the earlier technology of HitClip casings, Dupont took to the screens of OpenSCAD (+1 for certainly one of my favourite CAD instruments!) to script (sure, script) up an enclosure for the board we have seen above.
OpenSCAD is superb. It is a scriptable CAD language that lets you programmatically generate geometry primarily based on parameterized values.
This is a snippet of the 69 line script that created the above 3D mannequin.
See the block on the prime? Right here you possibly can tweak issues like PCB thickeness and width, and even variability for bundle heights in elements. That is awfully utility particular, however the idea is massively highly effective, and even will be prolonged to a scriptable animation engine, just like the OrangeCrab (🍊🦀!) instance beneath.
Whereas scripted CAD won’t be that intuitive at first, from parametrized PCB enclosures, to ECAD animations, OpenSCAD is very highly effective and positively a software to bear in mind for future initiatives.
A refined venture, completely offered.
With the PCB and case design taken care of, all that was left was to get a superbly polished printed half order positioned with PCBWay, for his or her UTR-8100 print service.
Whereas it is a bit onerous to make out the optical readability of this print choice, we have seen it earlier than in customized casework, and the outcomes actually are gorgeous.
The “GlassBoy” from Gunnar (@GmanModz) on Twitter is simply wonderful, and positively lives as much as its title.
It is no surprise Dupont selected to go for this selection right here, showcasing the atom-sized album artwork is a part of the enchantment of the HitClip cartridge, so going for an optically clear end is a no brainer!
From outdated music media, to on-line film streaming!
Get the remainder of the gory particulars from Dupont right here on this video he is printed on the venture!
For these nonetheless desirous to immerse themselves in additional particulars, you are in for a deal with. We have hyperlinks to a GitHub repo, a Hackaday venture web page, and naturally, Twitter for the birds amongst us — @gvy_dvpont.
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