Yet Another Mobile MP3 Player

When I got a new car in 1998 I built a player after deciding MP3 sound quality was good enough. Near the end of 1998 I had this player built and in service. For over a year I had no real remote control for it, and used a TRS-80 model 100 to control it. I didnít finish the wired remote control until 2000. The player fits under the passenger seat.

 

These pictures were taken during the final assembly stages. The dimensions are approximately 11 by 9 by 2 inches. I made the case from aluminum sheet and painted it with textured ďtrunk paintĒ, which hides mistakes nicely. The case contains a Tyan Titan III motherboard, right angle ISA riser card, 3Com 3C509B ethernet card, Soundblaster Vibra 16 sound card, Maxtor 3.5 GB disk, and a 12 volt power supply I built to fit. Itís basically a personal computer that runs in a car.

The CPU is an AMD K5 running 75 MHz. Thereís 16 meg ram, and the operating system is Linux (Red Hat 5.2). MPG123 handles the MP3 decoding, and I wrote a control program in Perl.

I built the remote control in an old Blaupunkt CD-changer remote case which I emptied completely. It now has a backlit 40x2 LCD and a PIC 16F84 microcontroller. It communicates serially at 2400 baud and also turns the playerís power supply on and off. It has a few inputs and can sense if the car stereo is on.

The old Tyan motherboard takes a long time to self-test, and a 75 MHz processor isnít very fast. Booting takes 90 seconds. I thought it would be neat to use one of the remoteís sense inputs to sense the electric door lock on the car, so it could start booting before I got into the car. The carís wire I needed to intercept was hard to get to, so I never bothered. It would only save a few seconds anyway.

This player has survived winter in central Oregon and summer in Phoenix. Before I built the remote Iíd have to manually turn the power off, and sometimes Iíd forget. I could still start the car after running 15 hours on the battery, and it also survived a few weekends when it drained the car battery to nothing. The battery didnít like that so much. In 2002 I built a faster, smaller player and gave this one to a friend. It still works fine and will be getting a larger capacity disk some day.

Download:
Power supply schematic yammps.gif
Wired remote control schematic yammrmot.gif
Perl software mp3pony.pl
Wired remote control C source code remote5.c
You can compile with the ďliteĒ version of PICC free from Hi-Tech Software or use the binary:
Wired remote control binary remote5.hex

License:
The hardware design and software are covered under the GNU General Public License.

Warranty:
None.

Frequently Asked Questions:

Q:

Isnít an AMD K5-75 slow? Doesnít that suck?

A:

Itís fast enough on the 2.0 kernel. System load when playing is 45 percent.

 

 

Q:

Whatís a non-inductive resistor made of 5 inches of wire?

A:

It doesnít really need to be non-inductive, just make a jumble.

 

 

Q:

Youíre not using it any more? Sell it to me!

A:

No, I gave it to a friend.

 

 

Q:

How do I get the binary into a PIC16F84 chip?

A:

With a PIC programmer. Here is one Iíve designed.

 

 

Q:

Where do I buy an Arnold Engineering toroid core?

A:

Frequently a large toroid can be found inside a PC power supply. It will be ferrite, not like the permalloy core I used, but it will work fine. Alternatively you can use a rectangular snap-on noise filter core available from Radio Shack. It will hiss unless you glue the halves together.

 

 

Q:

Is the sound quality any good? Do you get alternator whine?

A:

Sound quality is excellent. The Vibra 16 is a very simple sound card, perhaps thatís why. Audio is fed into my Pioneer AM-FM-cassette head unit through a ďP-bus line in adapterĒ. P-bus is Pioneerís CD-changer interface. The line input is balanced, not grounded, thereís no whine.

 

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