If cell phones have it, why can't we?

[BlackOpSource]

Okay. Cell phones are dumb and stupid because they're so utterly dominated by the cell provider; they're just not all that hackable.

However, as an iPod (5.5G Video) owner, I am annoyed by the fact that some people can listen to FM radio on a cell, whereas my FM reception on the 'Pod is truly awful. (That is to say, I have no antenna or software or anything.)

Before I go further, let me say that I know there are tuners out there for the iPod. I don't care. That's no fun, and I'm on a quest right now to distance myself from my 'Pod by buying/building hardware that is not dependent on my ownership of an Apple product. I'm doing the same for my music collection, too.

My question is this: What prevents me from plugging in my iPod's USB-to-iPod cable, letting it dangle free as a small, inefficient antenna, and having some kind of software (probably within Rockbox) to demodulate whatever signal comes in via the "line in" pin (normally used for microphones) to give me a nice, shiny FM signal?

Actually, I picked a bad comparison. Consider for a moment that I paid $250.00 for a virgin iPod Video that has NO radio capabilities at all. Consider also that I paid a mere $3,000.00 for a 1995 Ford Probe GT (That's my baby. *strokes spoiler*), that has all kinds of radio capabilities, way better bass than any earphones, surround sound, and goes WAY faster (Horsepower is a measurement that doesn't even APPLY to an audio player! What's that about?).

But really- and here's the clincher- I have a dying, poorly-cared-for, sticky-keyed Texas Instruments TI-83 Plus (graphing calculator), that, should I put the correct assembly program into its memory, could pick up AM radio (no FM, but still!) over one channel of its port via the included link cable, and play it in mono over the other channel.

It's like an open-source software/hardware arms race, and we're losing. But good luck, because I can't code.

(More seriously, is there any reason we can't do this?)

~BlackOpSource

EDIT: Wow. I hadn't even seen this post when I titled this. Wild.

[dan_a]

There is.

A USB interface is digital, not analogue, so you would not be able to receive radio signals on it.  The only possible place to read radio signals from would be a microphone input.  If I understand things correctly, to be able to demodulate any radio signal you need two samples of the in-phase and quadrature (I and Q) signals per wave period.  This basically means that for a normal 22kHz mono mic signal you can sample radio signals up to 5.5kHz.
The LW broadcast band starts at 138.5kHz, so we'd be a very long way out from being able to hear anything useful.

Look up "software defined radios" for more information - but this is off topic for Rockbox.

[saratoga]

My question is this: What prevents me from plugging in my iPod's USB-to-iPod cable, letting it dangle free as a small, inefficient antenna, and having some kind of software (probably within Rockbox) to demodulate whatever signal comes in via the "line in" pin (normally used for microphones) to give me a nice, shiny FM signal?

FM radio has a center frequency around 100MHz, (and AM around 1MHz).  Thus pure software demodulation would require a nyquist rate of more then 200MHz (2MHz).  The line in jack runs at 44khz or so.  If you want to do it with a resumable sample rate, you need analog hardware to demodulate the signal in advance, or at least a high pass filter so that you could undersample and reconstruct.  

But really- and here's the clincher- I have a dying, poorly-cared-for, sticky-keyed Texas Instruments TI-83 Plus (graphing calculator), that, should I put the correct assembly program into its memory, could pick up AM radio (no FM, but still!) over one channel of its port via the included link cable, and play it in mono over the other channel.

That only happens because your TI has shoddy analog design that allows it to (poorly) demodulate AM radio.  DAPs are designed not to do that.  If you want a radio, buy a player with one built in.

[BlackOpSource]

That only happens because your TI has shoddy analog design

Hey, now, let's not get too rough on the old calc.... I like that calculator. Also, it's digital. Check out ti-calc.org. There's more info there than.... Well, it's very informative.

Anyway, I didn't realize the line-in was digital. I thought that, like many things I've dealt with lately, you were just paying a bunch of money for a sleek interface, a cable to the iPod, and something with the "Made for iPod" thing on the side of the box.

Case in point: Car audio.
-To get an install for an Alpine head unit of a device that allows the stereo to control the iPod (There's the interface!) through a cable (Cable!) cost multiple hundreds of dollars, including about $200 just for parts (Stupid proprietary crap.).
-For me to order a special back-of-my-stereo-proprietary-jack-to-RCA cable from Hong Kong cost $7.00. It was exceedingly high quality, with gold contacts and stuff, and came in less than a week. I then purchased a 6-foot RCA-to-3.5 mm cable of similar quality from Radioshack. With a little elbow grease, I took apart the car's console, simply plugged in the cables, and threaded them out an existing hole into the car's center armrest storage. So, I saved about $200 or $300, maybe a day of waiting, and, when I fiddled around with the WPS, a totally seamless installation. And Rockbox. Also, and very important to me, if my iPod breaks, the car's line-in still works.

Now, I realize this doesn't address the fact that the line-in on the player is digital. But it does demonstrate the general feeling I have about the whole thing.


At any rate, thank you for the fine information on the limitations of the hardware.

~BlackOpSource

[saratoga]

That only happens because your TI has shoddy analog design

Hey, now, let's not get too rough on the old calc.... I like that calculator. Also, it's digital. Check out ti-calc.org. There's more info there than.... Well, it's very informative.

If you can hear audio, you have something analog. If you can hear EMI from radio stations, its bad analog.

Anyway, I didn't realize the line-in was digital.

Its not.  Its just a line in.  The processor is however, so the "some kind of software " you wanted will need digital input, which means even if you can feed the analog though, it wouldn't do you any good.

-To get an install for an Alpine head unit of a device that allows the stereo to control the iPod (There's the interface!) through a cable (Cable!) cost multiple hundreds of dollars, including about $200 just for parts (Stupid proprietary crap.).

Yes but thats because you're buying a high end head unit, and head units are expensive.  

[melancholydm]

if you really wanted radio on your mp3 player why did you even go and buy an ipod? they've never advertised to be able to play radio without the accesory. If you really wanted the radio on your ipod... buy the accesory, boot into the OF and listen to it, nothing prevents you from booting back into RB to listen to your mp3s

[BlackOpSource]

Anyway, I didn't realize the line-in was digital.

Its not.  Its just a line in.  The processor is however, so the "some kind of software " you wanted will need digital input, which means even if you can feed the analog though, it wouldn't do you any good.

Ah. Now I get it.

-To get an install for an Alpine head unit of a device that allows the stereo to control the iPod (There's the interface!) through a cable (Cable!) cost multiple hundreds of dollars, including about $200 just for parts (Stupid proprietary crap.).

Yes but thats because you're buying a high end head unit, and head units are expensive.

No, no, you misunderstand me; I bought this car used back in December, and it came with an Alpine head unit (installed back in 2002) that supported the iPod interface (I think. I also checked this same thing out on my last car, which had a Pioneer head unit in it.). The cable and setup cost multiple hundreds of dollars, without factoring in the cost of the head unit. I just thought the whole thing was stupid and tethered you to Apple, so I decided to forgo it.

if you really wanted radio on your mp3 player why did you even go and buy an ipod? they've never advertised to be able to play radio without the accesory. If you really wanted the radio on your ipod... buy the accesory, boot into the OF and listen to it, nothing prevents you from booting back into RB to listen to your mp3s

Woah. Who peed in your Cornflakes?

One- I didn't really want the radio on my iPod. I just had an idea that seemed like a good addition to Rockbox, and I wanted to check it out technically before formally suggesting it as an addition.

Two- You'll notice that I said I didn't like being tethered to my iPod. Really, what I mean there is that if my iPod should break (God forbid!), like my old Nano, I don't want there to be other factors (accessories, copy-protected music, et cetera) preventing me from buying whatever the hell I please. This applies to other players as well. So no iPod radio for the original firmware.

Three- They've never advertised being able to play Doom out of the box, either. And yet, with a little poking around, here I am. As I said earlier (see point one), I was wondering about the technical feasibility of a.... Well, is "hack" the right word? You see my point?

~BlackOpSource

[saratoga]

No, no, you misunderstand me; I bought this car used back in December, and it came with an Alpine head unit (installed back in 2002) that supported the iPod interface (I think. I also checked this same thing out on my last car, which had a Pioneer head unit in it.). The cable and setup cost multiple hundreds of dollars, without factoring in the cost of the head unit. I just thought the whole thing was stupid and tethered you to Apple, so I decided to forgo it.

If your headunit actually supports the Ipod, you shouldn't need anything.  It'll just dock to the ipod like a PC.  

It sounds like you're describing one of those adapters that takes an older head unit that doesn't support the Ipod (as yours surely does not given that it was from 2002) and provides the interface logic to glue the Ipod to whatever proprietary interface your head unit includes.   In this case its expensive since you're basically buying a second head unit minus the amp and putting it in series with your existing head unit.

[BlackOpSource]

This topic in a nutshell:

"ya i was thinkin we cld put fm radio on rb??!!?11?"
"no we cant"
"o rly? y no fm?"
"cuz tech stuff and shut up"
"o rly? well head unit!"
"ya rly!"
"k!111"

This is the part where I say "k!111". That explains quite a lot. Thank you.