This is Hacker Public Radio Episode 3,809 for Thursday 9 March 2023.
Today's show is entitled, The Abominable Post Apocalyptic Podcast Player.
It is part of the series, Arduino, and related devices.
It is hosted by McCutriniic and is about 20 minutes long.
It carries an explicit flag.
The summary is, build a $3 MP3 player in one hour.
Greetings, this is McCutriniic.
So I broke on my slave slabs that I used for podcast listening, and I get almost my energy
from solar, so I can't be just listening to podcast on a laptop, and plus it's not very portable.
So I wanted a podcast player that's portable, and so I ended up creating an abomination.
I wasn't happy with the look of it for quite some time, and I'm still not, but I use it all the
time every day, most of the day, most of the night.
So there's something to say for this design, I guess.
It's also a feature, you know, because it looks like garbage, so it'll be a useful feature for
post-pocket with the robots when the townies get tired of the robot, stealing all their solar panels,
and plugging into their outlets, stealing their power and stuff, the robots might get persecuted,
and have to disguise themselves as trash.
So speaking of trash, there's only two components that you should need to buy, maybe three,
and I'll put the links up to AliExpress.
There's the 18650 charger, which you can use to charge an 18650 cell.
So you might need to buy a cell, but I got all mine for free. I've got about a hundred of them stockpiled,
and you can find them in things like laptop batteries, power tool batteries,
that are lithium ion. Be extremely careful taking them apart, where gloves use pliers.
The most dangerous thing about batteries, I've found is the risk of getting cut on those internal
conductors in the batteries between the cells, because they just use these pieces of metal,
and when you cut them off, they're extremely sharp, so that's that. And MP3 decoder,
this MP3 decoder is based on the GPD2846A chip, and we're going to look at the database for that,
and look at some very ripe hacking opportunities, like unexport hacking opportunities in this thing.
But for now, we're just going to wire it up for the functions that are on it. So on this MP3 decoder board,
you see the SD card to the left of it, the SD card in it is colored red and gray. It's just
barely sticking out, and it has three sets of pads that go to ground, and once set of functions
for each pad. So you're meant to put a switch across these two pads. You can't see them in the
diagram. I mean, you can't see them in the picture here, because they're obscured by my soldering job.
I've actually got six wires connected there for the three momentary switches that are on top of it.
But if you look at the Ali Express link, you can see a clean version of this and look at the pads.
So these pads are active low, meaning the switch shorts to ground, which means you can control
them from Arduino, which I did with my other robot project. The hero robot project, go to bitchube.com
forward slash channel forward slash mechatroniac to see that in action. If you listen to my previous
podcast, where I've encouraged you to get Arduino's, and you haven't, you're not too bright,
because it costs about twice as much now, but there's still very much worth it. So I put a link into
a, I put a link to an Ali Express page with a sensor kit that comes with Arduino and a bunch of
sensors and things across about 50 bucks. Could have had it for about 30 or something, a year or so ago,
but it's very much worth it still anyway. And that has things like the ultrasonic sensor and the
infrared sensor, which would enable you to do as I did and make the MP3 player attached to your
robot be controllable by a PV remote. But I wanted to leave that alone, and so I had this other
unit in my box. So the, the one that I've gotten my robot actually has four functions, and it's a little
bit past here, a little bit more expensive. This one's like a budget dollar cheaper. It's like a couple
of bucks just extremely inexpensive, very good, very good deal of best price. But the other one had
four buttons on it. It had a jack for headphones and also USB input. So this one just has the
SD card. Although this chip has the USB capabilities as well, but we'll get it to that a bit later.
So the, the wiring is pretty straightforward. There's three momentary switches. All of this stuff
other than the two boards, like I got posted, I'll pop a lipstick style. And if you're like me,
you've got stuff like this, post a pop lipstick. These chargers, they come in strips of five,
so you break them off on any time as you need them. And they have a micro USB input. So
just plug in a micro USB when you want to charge it up. You can just treat this as a black box
for all purposes. There's only two sets of leads going out because the input is the USB that's the
power. And then the D plus and D minus guess where those go? Straight to your 1860 cell or any other
nominal 3.7 volt lithium ion cell. You can use those gel packs as well. And the output, so
and the output goes to the positive goes to the positive end and the negative goes to the ground
on the MP3 player. You can't see it because it's a little bit obscured by the wires. You can sort
of see it. And speakers, SP minus SP plus that's self-explanatory as well. So for these momentary switches,
I bought these LED lights, they're on sale for like a string of 50 lights for three bucks or something.
I bought a bunch of those and each of them had this momentary switch with little
cell battery and it so you could test the lights in the store. And that's it. That's the end of the
use for it because we're supposed to put batteries in but I've modified these USB power packs. But
anyway, those momentary switches, I took the little cells out and connected them up and I'm using
them as momentary switches. So those are supposed to be thrown away. But using them. Okay, so
yeah, I can't believe that's all the wiring pretty straightforward. So the build itself
happened to find this jar. There's a high resolution for you can see what kind of jar it is.
3.5 grams size. And it just happens to be the perfect dimensions as a speaker box for this
like two-inch speaker that I found. So the reason it's so awkward looking and kind of like a modern art
looking is the speaker magnet is pretty big. And the 18650 cell is so long and I'm gamely I have
put it under this big black lid. Some jar jam lid or something like that. But the 18650 cell
just fits right in there. And I've got the wires from B plus and B minus soldered directly to the 18650 cell.
It's the note about safety and soldering can have concern my last video about taking
apart the batteries and making I think it was the one about my battery pack and soldering on
to cells. But I found that the like I said again the the most danger is going to be
taking them apart. Number one. Secondary danger is burning your house death and if you puncture
one. But they smell really terrible. So you'd probably be able to throw it out. You have
pair of pliers and take it outside. They will alert you. But the 18650 cells have a safety mechanism
where before it'll blow it it's got a mechanism where it'll release the pressure. So they've got
that safety built in. But I've never activated it. I don't know you'd probably have to try pretty
hard to to make it explode from heat. Just that's just from my experience. Obviously if you are
soldering you want to use you know take as little time as possible. Maybe if it's hard to
solder on like some surfaces seem to solder phobic almost I know for a fact some are really
hard to solder to. So if it is try sandpaper or something there's tutorials on YouTube people using
spot welders made out of batteries. So that would be it one way to go. But I find solderies quite
adequate. If you're really phobic about soldering on to a cell you can use one of those
elastic bands from a broccoli. I don't know the Canada we have these these broccoli holder elastic
bands. But you can you can strip the wires and just put the band over the cell and just talk
those wires in appropriately purplearity and just go with that. I'm actually doing that with one of
my solar powered chargers because I can't find my my little cell holder you can also order the
cell holders as well. If you're ordering an 18650 you want it to be neat you can get a cell holder
that you could just clip in as well. But anyway the cell is just hidden right under the big black
lid and yeah like I said these these these wires go down from the from the switch pads where they
don't have to they could have just gone up. But I was going to have the switches be at the bottom
and have them just kind of have the the player just kind of stand on the switches but they're
kind of hard to align properly because the fun was the thing isn't perfect. So I send up putting
them on top and I was too lazy to do the resaudering again so I just got them got the wires coming
back up from the top hopefully you can make yours look more elegant or not the anti aesthetic
is a feature after all robots might have to hide. So I think that's it yeah so yeah you probably
make it smaller if he use a different type of cell and smaller switches and you know put the cell
inside the container bonus points if you put your stash in there too and have it removable. But this
works the the first time I used one of these for the robot I bought of amplifier module as well because
I thought oh it's going to have a really weak up for it right maybe for headphones at the most
but I was surprised these things actually crank pretty good for their size got a little off
my apple out there and must be pretty efficient because they never get hot or even warm so
so you get pretty loud did I just like you out and you just think the show was any so
it was pretty hard to track down the data sheets but I've got some there's one in
Chinese that has diagrams of applications and there's one in English which doesn't have the
diagrams but it's in English so there's quite a lot of features that you can unlock with different
resistances so I just started looking at this I just brought this up for the podcast but if I
had looked at it before I sealed it up which I used oh by the way I used tape to hold it together
this put tape I guess I forgot I mentioned how I'd put it together it's it's just like
gorilla tape and some electrical tape taping down the speaker to the container and then
more tape holding the lid and then hot glue holding the USB charger and the MP3 decoder board
and the lid has cutouts on it but you can see one diagram you can see a little slit cutout
for the SD card and the other side you can you can see it in it it's got a nice LED when it's charging
it's gonna put some nice glow when it's charging at night all right so looking at the data sheet
it shows it shows up to eight buttons here with various different resistances so the one board
had that had only three the other the other one had four but it's got up to eight maybe even more
it's also got line in this device is it puts out a mixed mono but if you he can solder lines off
right with some magnet wire I guess solder right left off and put that to an amplifier if
you want stereo out of it so the chip itself the decoder chip does stereo it puts out FM clock
whatever that means it's got some applications where it shows an FM chip so it supports
three different type of FM chips so in this game control the what band and what frequency the
well yeah it's gonna be FM band and to it control what frequency the FM's gonna be off
so yeah all all of the functions are from one pin can eight IOA for its labeled and it says eight
to D key buttons but we know it's much more so the key definitions previous next play pause volume
up volume plus oh the functions on on this one are play and pause one button with a short press
it plays the previous MP3 with a longer press it turns down the volume and the other button
with a short press it plays the second or the next MP3 with a long press it turns up the volume
and that should that probably conforms it shows a different configurations depending on like
there's a I guess it's a pull up resistor that you put from the BC 3.3 volts through a 22k
resistor onto the line off of this pin eight and then all the resistors come off of that to
the separate switches you'd be best to off looking at the data sheet for that but Chinese data sheet
and it shows the little diagrams of the switches the Scott and alternate mode as well and it
shows how to hook up the FM receiver chips as well it says it supports three different type of FM
receivers so nobody on YouTube has stepped up to unlock any of these features on these boards
there's a bunch of videos people hooking up the boards but nobody's unlocked all these features
here I'll read the features now volume scan scan all FM so I got through the basic ones there
scan plus scan minus channel plus channel minus skip to the next frequency of saved FM
radio you can save radio stations wow I'm the how you do that mode mode switching in sequence
SD card T card you disk FM line in wow you kind of do a lot with this thing a line in
very interesting so I see we'll cut down automatically if the mode is selected up the expected
peripheral is absent repeat treating the keys again repeat into cycle mode switch all
and single cycle and each year which I managed to get this i managed to activate the
EQ feature in the one on my robot with the resistor I forget what resistance yeah so you could be
you could be one of the you could be one of the pioneer hackers of this chip
unlock these frequencies on thanks for Canon Day for making the MP3 links visible on the main page
there hpr let's meet download easier now that I'm not using a podcast app strange how they make
things harder on computer and antenna pod doesn't exist on desktop or laptop whatever all right
so yeah very versatile this is just the basic thing uh so I encourage you to get this get an
Arduino get a kit if you just want to make an Arduino that's activated activated by you could
get an activated by PIR whatever have some walk by and play an MP3 I mean this this thing
it also have some pretty good prank utility as well like hide it and make like a really long
MP3 and have like scary sounds you know stuff breaking your animals or whatever or make it
make it remote control well like I said it's not much to spend to it's not much to spend
to be able to use these micro processors and these cool boards and you know get to know these
these little chips by their data sheets and stuff it's a lot of fun and the more you do the
better you get at it so either way you want to go anti aesthetic or make yours actually elegant
you know use some some boxes that make sense and don't look like garbage either way
it's a feature you have been listening to hacker public radio at hacker public radio.org
today's show was contributed by a HBR this night like yourself if you ever thought of recording podcast
click on our contribute link to find out how easy it means hosting for HBR has been kindly provided
by an onsthost.com internet archive and our synced.net on the satellite stages they show is released
on their creative comments attribution for pointo international license.