construction details.mht

一个基于AVR单片机的大屏幕mp3

board.</P>
<P>J8, the DB9 debug connector, is only required if you plan to do some =
software=20
development. If you write code for the player you=92ll find the debug =
port useful=20
for printing status or error messages. If you don=92t plan on being a =
=93code=20
monkey=94 you can leave this connector off. You'll need to be "firm" to =
make the=20
spring clips on each end of the connector click into the PCB. Be =
careful, but be=20
firm.</P>
<P>&nbsp;</P>
<H3>LED, LCD Backlighting, and InfraRed</H3>
<P>I suggest putting small connectors in the board for D4 (the LED), U8 =
(the=20
infrared receiver) and J10 (power for the LCD backlight). You will =
likely attach=20
all three of these devices to your front-panel in some semi-permanent =
way. In my=20
case I=92ve glued the LED and infrared receiver into holes in my box =
front panel,=20
and the LCD backlight is (of course) on the LCD which is bolted in. =
Having=20
connectors on the PCB for their leads makes it easy to remove the PCB =
from its=20
enclosure without having to do any painful disassembly. Exactly how you =
do it is=20
up to you, but the hole size for these components is chosen to make it =
fairly=20
easy to do. The kit contains both male &amp; female connectors for this=20
purpose.</P>
<P>The photo below provides a rear-view of the LCD display and =
pushbuttons=20
mounted in a simple panel. The LED can also be seen, with it's red &amp; =
black=20
wires. I used a blue LED because it's fun, but you can pick any colour =
you want.=20
It's just glued in there. The LCD display and pushbutton PCB are simply =
bolted=20
in to the panel. On the left you can see the grey ribbon cable =
interconnecting=20
the two PCBs. This particular LCD in the photo doesn't have a backlight, =
so=20
don't bother peering at the photo too hard looking for it. </P>
<P align=3Dcenter><IMG height=3D288 alt=3D"MP3 Player LCD Display =
Mounting"=20
src=3D"http://www.frankvh.com/mp3player/DisplayRear.jpg" width=3D292=20
align=3Dmiddle></P>
<P>Be careful with your connector orientation for the LED and the IR =
receiver.=20
In the kit I provide polarized connectors for these parts so you can =
easily make=20
up a little cable appropriate for your enclosure. Be certain that when =
you make=20
your cable you get the wires the right way around; you don't want to =
power the=20
IR receiver backwards! That'll kill it for sure.</P>
<P>&nbsp;</P>
<H3>IDE Connectors J5 &amp; J6</H3>
<P>The kit contains two IDE connector headers: </P>
<UL>
  <LI>a 40-pin 0.1" spaced header for J6 which is used for 3.5" disk =
drives=20
  (regular PC disk drives), and;=20
  <LI>a 44-pin 2mm spaced header for J5 which is used for 2.5" laptop =
drives.=20
  </LI></UL>
<P>Only install the <EM>one</EM> header that you need. Do <EM>not</EM> =
install=20
both unless you actually need to swap between two different disk-drive =
types.=20
(Note that you can only have one diskdrive plugged into the player at =
any one=20
time.) When one connector is cabled to a disk drive the other connector, =
if=20
present, acts like a stub on the IDE bus, reducing the quality of the =
IDE bus=20
signals. To avoid this stub effect, only populate the one IDE connector =
that you=20
need. </P>
<P>If J6 (the 40-pin header) is used, remove pin 20 from the header =
before=20
soldering it into the board (kit connectors normally come with this pin =
already=20
removed). This allows the use of an Ultra-IDE diskdrive cable, which is =
the=20
cable with the extra ground wires in it. Just out of interest, take a =
look at=20
the IDE connector on your 3.5" diskdrive: on any remotely modern drive =
you'll=20
see that pin 20 is missing there too. (That's also a good way to =
double-check=20
which pin is pin 20 before puling it out of the header.)</P>
<P>&nbsp;</P>
<H3>J7, the ISP Connector</H3>
<P>This is a simple 10-pin header. Use the keyed version (ie the one =
with the=20
little notch cut out the side). It=92s oriented on the PCB to allow use =
of a=20
right-angle version. If you use a right-angle connector you can have it =
poke out=20
the rear of your box, allowing you to reprogram the player without even =
having=20
to open the box. Recommended, and this is what is provided in the =
kit.</P>
<P>&nbsp;</P>
<H3>The RCA Connectors &amp; Fuseclips</H3>
<P>Fiddle with the two RCA audio connectors a little before soldering =
them down.=20
Make sure you know how they best mount on the PCB. They will sit flat on =
the=20
PCB; they shouldn't be pointing up at all.</P>
<P>The fuseclips are a little trickier. Make sure you have them the =
right way=20
around! Otherwise your fuse won't clip in. Oops. You may find it easier =
to mount=20
a fuse in them, then solder that whole little assembly down. You may =
find it=20
easiest to lightly solder the fuseclips from the top of the PCB while =
you hold=20
them upright. Then once they're standing straight of their own accord =
you can=20
flip the board and solder them in properly from the bottom of the =
PCB.</P>
<P>&nbsp;</P>
<H3>The Assembled PCB</H3>
<P>The photo below is of an assembled rev 2 PCB. Those with sharp eyes =
may=20
notice a resistor missing towards the top left of the photo. (OK, so =
it's not=20
<EM>completely</EM> assembled!). This photo should give you an idea of =
what the=20
end product may look like. Click on the photo for a larger view.</P>
<P align=3Dcenter><A =
href=3D"http://www.frankvh.com/mp3player/PCBfullsize.jpg"=20
target=3D_self><IMG height=3D400=20
src=3D"http://www.frankvh.com/mp3player/PCBsmallsize.jpg" width=3D453=20
border=3D0></A></P>
<P>&nbsp;</P>
<H3>Disk Drive Power</H3>
<P>If you use a 3.5=94 drive you=92ll be using power connector J2, as =
well as IDE=20
connector J6. If you use a laptop drive you won=92t need power connector =
J2, as=20
the laptop drive draws its power from IDE connector J5.</P>
<P>J2 is a standard disk-drive power connector on short (two or three =
inches)=20
wires. Where to get one? If there=92s a PC being junked anywhere, snip a =
connector=20
off its power supply. Alternatively, go to your local computer store and =

purchase a =93Y=94 disk-drive power cable. This is a little cable that =
breaks a=20
single power-connector into two. One of these gives you two disk-drive =
power=20
connectors.</P>
<P>&nbsp;</P>
<H3>Mounting on a 3.5=94 Drive</H3>
<P>The four big holes on the board line up with the mounting holes in =
the bottom=20
of a 3.5=94 drive. Yes, it=92s fine to run the drive upside down; drives =
don=92t care.=20
The board is laid out so that the end with the audio, power, USB etc =
connectors=20
overhangs the end of the drive, to allow these connectors to poke =
through the=20
back of your box without having to run any messy wires.</P>
<P>I=92ve found that the player seems to be happier if there=92s a metal =
shield=20
between it and the drive. I suspect that noise radiating from the drive=20
sometimes affects the player. I cut a little piece of metal flashing =
from the=20
local hardware store to size, drilled 4 holes in it, and installed it =
between=20
the drive and the PCB. Using threaded standoffs made it pretty simple. =
See the=20
Rev 1 mounting photo below. (I will put up photos of the rev 2 board =
once I have=20
it mounted in a box.)</P>
<P align=3Dcenter><IMG height=3D225 alt=3D"Rev 1 Homemade MP3 Player =
Assembly"=20
src=3D"http://www.frankvh.com/mp3player/Rev1Assembly.jpg" width=3D422=20
align=3Dmiddle></P>
<P>The black thing on the bottom is the drive. You're looking at it =
side-on.=20
It's bolted to the box floor with the help of a bent piece of metal. =
Threaded=20
standoffs are used to mount a metal sheet above the drive. You're =
looking at=20
that edge-on. Then another set of standoffs to support the PCB. The =
colourful=20
ribbon cable on the left is the IDE cable. You can see that the =
assembled drive,=20
metal shield and PCB makes a neat and simple self-contained "brick" for =
bolting=20
down into a box.</P>
<P>Here's a photo from the front of an LCD (non-backlit in this case) =
and=20
pushbuttons mounted in a simple panel. The panel has a rectangular hole =
cut in=20
it for the LCD and some drill-holes for bolting everything in as well as =

allowing the pushbuttons to protrude through. Not a great photo but you =
get the=20
idea:</P>
<P align=3Dcenter><IMG height=3D412=20
src=3D"http://www.frankvh.com/mp3player/Rev1Front.jpg" width=3D477></P>
<P>&nbsp;</P>
<P>&nbsp;</P>
<H3>Powering Up The Board</H3>
<P>Now that you've soldered in all of the components, it's time to power =
up. Do=20
a careful double-check of everything. Take your time. If you've made a =
mistake,=20
better to find and fix it now before you power up and smoke something. =
Good=20
light and a magnifying glass can be helpful. If you built from a kit =
there=20
should be no empty component spaces on the PCB, with the exception of =
one of the=20
IDE connectors. So if you spot an unpopulated resistor or capacitor site =
you're=20
guaranteed to have missed something.</P>
<P>Disconnect any cables, except the LED (if you have it connected; no =
big deal=20
either way). Make sure you have the drive, LCD display, etc all =
disconnected. In=20