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 didn’t 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 “trunk paint”, 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. It’s basically a personal computer that runs in a car.
The CPU is an AMD K5 running 75 MHz. There’s 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 40×2 LCD and a PIC 16F84 microcontroller. It communicates serially at 2400 baud and also turns the player’s 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 isn’t very fast. Booting takes 90 seconds. I thought it would be neat to use one of the remote’s sense inputs to sense the electric door lock on the car, so it could start booting before I got into the car. The car’s 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 I’d have to manually turn the power off, and sometimes I’d 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 didn’t 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.
You can click on these for bigger images or for printing/downloading.
MP3 Playing Software (perl)
Remote Control Code (C)
Remote Control Firmware (hex)