Car MP3 player
In local supermarket I bought small car MP3 player. It cost about $25 (79Ltl). It is USB MP3 player with FM modulator. Just plug it to cigarette igniter socket, tune car radio, put your USB flash memory stick and enjoy the music.
I didn't hope to receive good quality sound from such cheap device, but the real situation is much worse. The sound is full of interferences. Especially when there is some pause in your music. The interference is dual- from the car itself and from USB player.
Both interferences are solved in different ways. So, first of all, we must disassemble the device. It is very easy, just unscrew the fuse holder and remove the ring.
Inside you can see three PCBs: indication and control, FM transmitter, MP3 player and PSU. The red wire is just antenna and it tends to tear off. It goes from transmitter to car’s +12V line. So the car’s electric lines acts like big antenna.
That yellow capacitor is added by myself. This is the part of the struggle against interferences from MP3 player’s CPU and USB line. I also added one 470uF capacitor to USB connector. This decreased “reading from USB" noise.
The PSU of the player is very simple. (Component name come from silkscreen.) +12V from the automobile, L1 choke (too small to be significant), 22uF 16V (c17) capacitor, U5- UTC78D05L linear regulator, small ceramic cap and 100uF 6V tantalum capacitor. Now there are two linear regulators U2 for U4 for 3.3V and CPU BU9432-C1 Vcore. The CPU is made by Rohms. The comapny is very ugly- they didn't publish datasheet of their products.
There is possibility to find player with switched regulator- there PCB traces for some small Switching Regulator instead of U5 and landing places for U1, D1 and L?. The Switching Regulator is much more economic device but more noisy. The power drain is quite big, as I replaced the fuse with appropriate inductor and it melted.
I found only this information about MCU and I only discovered that there are more features of the MCU than it is used.
The BU9432-C1 and BU9434-C2 audio system processor ICs implement a USB 2.0 full-speed host controller, an MP3 decoder, a D/A converter, and a system controller—allowing playback of MP3 files contained on flash memory via USB. The BU9432-C1 features a headphone amplifier, while the BU9434-C2 incorporates an SD card interface controller, a sound effecter, and I2S/SPDIF interface support.
The chips' MPEG audio 1, 2, 2.5 decoder features a sampling rate of 8 to 48 kHz and a bit rate of 8 to 448 kbits/s, VBR. The D/A converter has 0.03% distortion, a 93-dB SNR, and an 88-dB dynamic range. The ICs have a FAT file system and are offered in TQFP64V and VQFP64 packages. ($5 ea/1,000—8 to 10 weeks ARO.)
The FM transmitter and stereo encoder is made on HY1417LP chip. I didn't find any useful information in the internet about it.
Also, there is small serial RAM using 24C02 chip. It must store some setting in it, but I didn't find it working, as after power-off the player starts playing from the beginning of the playlist.
On display and control board other chip, AM81SA10705, is placed. It is some sort like LED buffer and serial-parallel converter.
October 8th, 2007 at 4:51 am
I ordered a naked version of one of these from http://electronics-diy.com/store.php?sel=kits.
Unfortunately the seller didn't have any information on the chip either. I emailed Rohm and they sent me an email back saying the person who handles questions was on vacation and couldn't get back to me right away, but they did send me a catalog of their various chips. The catalogs didn't have any useful information in them either, not even prices. They were very useful as packing material for items I needed to ship. I contacted them over 3 months ago and they haven't gotten back with me. That’s one hell of a vacation. I plan to contact them again and see if I can get some sort of fire lit under their asses. If I get anything (useful) from them I'll forward it to you. I would like to know if you can help me a little with the one I have. As I typed earlier the one I have was naked. It had no case and the simple instructions that came with it simply gave the buttons commands. I would like to know if you could send me via email a copy of the instruction manual that came with yours or at least let me know what mode the LEDs are supposed to represent (repeat, random, etc). Thanks.
October 9th, 2007 at 1:58 am
I was emailed a PDF for the BU-9431-D1. Not an exact match, but close enough. Send me an email and I'll forward it to you.
January 7th, 2008 at 5:12 pm
if you have the datasheet of bu9432-c1 or bu9431 and hy 1417lp, kindly e-mail me.
thanks in advanced
rahimkv india.
January 16th, 2008 at 1:03 pm
Hello
I also buy MP3 player like you ( same as photo ) .I would like to chang frequency in all FMM band ( 87 to 108 ) .I work with many synthesizer frequency IC but I didnt find any info about HY1417LP . Do you
know how data for chose frequency send to HY1417LP? with which pin ?
best regrds
January 16th, 2008 at 5:00 pm
Read Lithuanian version comments. There is some datasheet information: http://www.vabolis.lt/2007/01/24/mp3-grotuvas/
February 6th, 2008 at 6:09 pm
http://www.dzsc.com/data/Circuit-8109.html - look for circuit and data of hy1417lp. pozdrawiam andy
February 20th, 2008 at 9:28 pm
the same IC is used in a thomson-brand radio/alarm/clock type cd340usb which I recently aquired for 15€
I'd be interested in the datasheet, too.
Although it seems that there is not much to discover. I got curious as it detects mp3s that have been deleted. maybe the fat is damaged!?
February 22nd, 2008 at 10:20 am
The IC couldnt play mp3s off a 128mb usb-stick dos-formatted on an older macos x (10.3.8 ?).
no problems with fat32 formatting on windows.
February 28th, 2008 at 2:20 am
The FM tramsmitter is the BH1417 from Rohm…lot’s of info on the net…!
http://members.home.nl/c.k.rf-design/
The USB controller has 2 versions, C1 and C2, C1 is standard (no more options), C2 has an Eq, Sound enchanger, enz enz
Have fun…!
March 5th, 2008 at 9:13 am
Could e-mail me the datasheet of am81sa10705 if you have?
Thanks.
Logger.
March 14th, 2008 at 6:04 am
Sorry for not responding sooner. Very busy. A small line of text from the email sent to me said “Please note that the 1st generation of ROHM’s memory host + media decoder solution was to be released as BU9432; however, the part number that actually went to mass production was BU9431″. That means the 9432 is the same as the 9431. I don't know what your emails addresses are, so I'll post my email here. Send me an email with the subject line of “Rohm BU9431″. My email is “moc.liamtoh@timmaj". It’s typed in backwards to fool spammers.
March 14th, 2008 at 6:30 am
I'm an idiot.
My backwards address is moc.liamtoh@999timmaj.
March 26th, 2008 at 9:46 am
It is possible to make in the given device function of memory at switching-off ?Here that has found: http://download.chinadz.com/IC_PDF/R/ROHM/BU/BU9432.pdf