The Install (version 2)
This version of the car computer is partially built.
The Processing Unit
The processing unit is built around an
Advantech PCM-9373 3.5" biscuit PC. Storage takes the form of a flash
disk-on-module for the boot drive and a compact flash hard drive for media
storage. The board is loaded up with 256Mb CL2 PC133 SODIMM memory. The hard
drive sits under the main board, and the power supply and shutdown controller
are destined to be mounted over the main board. In this way, it is anticipated
that the system will end up being around 6"x4"x2" in size, approximately half
the size of the previous system.
Storage
The operating system is
booted from a flash disk-on-module. A zipped image of Windows 98, cut down
considerably is unzipped from flash drive to a ram disk, and booted from there. The
zipped image is about 22Mb, unzipped it grows to about 48Mb. The system boots from
cold in about 17 seconds (until desktop appears and the hourglass vanishes). An
8Gb compact flash drive is used for the media storage. Approx 1Gb is devoted to map
tile storage, and the remainder is available for music. The map tiles are stored as
bitmaps compressed to DXT, zipped with zlib and packed together in larger tile files.
This provides good loading performance since the tiles are in a render ready
compressed form, and low memory and hard drive usage since they are compressed.
The Control Unit
The is a combination of an 800x600 TFT panel for the display, and a 4-wire
resistive touch screen overlay. The TFT panel is a Toshiba display LTM08C351 (I
acquired a pair for £26 from Ebay...!), hooked up directly to the motherboard
via a
PCM-3540R LVDS interface for a good quality image. The LVDS interface
allows a 10 wire interface with long signal cable capability. A TDK
CXA-P1212C-WJL inverter will be used to power the 350cd/m
2 backlight.
A penmount USB touchscreen controller interfaces to the 4-wire AMT touchscreen.
The screen was molded into a dash piece bought from ebay. The screen will go
where the heater controls and central vents are, and a screen in the frontend
software will be used to replace and add to this functionality. 3 high torque
servos will be used to move the heater controls, high side drivers or relays
will control the fan and heated rear screen.
The Power Supply
The PSU is another custom affair. Based around re-used components from the Mk2
Power Supply from the first car computer, it uses a PT6625 for the 5V supply
required for the motherboard. The optional 12V is supplied by a PT5071. This
also powers the screen backlight. Since the intended operating system is no
longer DOS, just cutting the power is not enough. A simple shutdown controller
based around a 12C508 was added to manage the soft and hard shutdown functions.
An open collector transistor presses the power button on the motherboard 15
seconds before cutting the power.
The head unit modifications
The head unit modifications are essentially identical to the ones used for the
first car computer. The switch on line from the head unit to the carputer is no
longer required and will be removed. Future plans involve using a 12C508
microcontroller to manage the switch over from radio to aux-in, to mute the
output whilst the switch occurs. This will avoid the loud thumps that can occur
with the previous setup.
The software
The software is likely to be considerably easier to write than for the original
system. I am not anticipating the need to write an mp3 codec, an ogg vorbis
codec, sound card drivers or VFD drivers this time around, and I have a lot
more processing power so optimisation will be less of an issue. It will also be
nice to have a C++ compiler to work with (The Watcom C++ implementation was
somewhat lacking in places). However, dispite all the changes, there are some
features of the original player I do wish to retain, specifically its speed
when loading. I shall be producing some software to integrate existing audio
and video codecs, whilst retaining the pre-compiled playlist concept. The screen
shots below are from a very early version, and have improved considerably in
appearance and usability.
The software is spread across several screens, the first of which is the GPS
screen. This gives a zoomable 2D map with the current location indicated. The
map scrolls as necessary. Datum points were placed to tie longitude/latitude,
and a delauney triangulation used to generate a mesh between those points.
Since each datum point has a grid coordinate on the map, we can use barycentric
coordinates to turn longitude and latitudes into grid coordinates to display
the correct part of the map. The padlock icon unlocks the cursor and allows
free roaming over the map by touching the map in the direction to be viewed.
The buttons to the top right allow selection of the music player functionality.
The next screen allows you to select an album to play. Touching an album entry
takes you to the play screen. The question mark button takes you to the search
page which allows you to find a specific song or artist. The list displays
album title, and where entered, the album artist. The buttons to the top right
allow selection of the GPS player functionality. The list of albums and songs
is built automatically from ID3 and similar information in the songs, and saved
in a binary format to be loaded almost instantly.
The on screen keyboard alows you to enter a search term for the music database.
The scroll window updates in real time as the search term is altered. Any songs
that contain the search term in the song title or artist name are displayed,
along with the album the song is part of. Touching any of the search results
starts playing that song from the album it lives in. To return to the search
screen from the playing screen takes just two touches of the screen, and the
search time can be refined/altered as necessary.
The playing screen lists the album being played, highlights the song currently
playing and allows you to switch to other songs. Touching the album name allows
another album to be selected. Touching an song starts playing that song. The
usual controls at the top stop, pause, play, and skip to previous and next
songs. The formats supported are limitted only by the DirectShow codecs
installed. Mp3 and Ogg Vorbis codecs are easy to find and install.
Disclaimer
I TAKE NO RESPONSIBILITY FOR ANYTHING YOU DO TO YOUR OWN CAR OR STEREO SYSTEM
USING THIS INFORMATION. THIS INFORMATION IS PROVIDED PURELY AS A GUIDE TO WHAT
I DID TO ACHIEVE THE EFFECTS I DESIRED, NOT AS INSTRUCTIONS FOR OTHERS TO
FOLLOW.
The Processing Unit
The processing unit is built around an
Advantech PCM-9373 3.5" biscuit PC. Storage takes the form of a flash
disk-on-module for the boot drive and a compact flash hard drive for media
storage. The board is loaded up with 256Mb CL2 PC133 SODIMM memory. The hard
drive sits under the main board, and the power supply and shutdown controller
are destined to be mounted over the main board. In this way, it is anticipated
that the system will end up being around 6"x4"x2" in size, approximately half
the size of the previous system.
The operating system is
booted from a flash disk-on-module. A zipped image of Windows 98, cut down
considerably is unzipped from flash drive to a ram disk, and booted from there. The
zipped image is about 22Mb, unzipped it grows to about 48Mb. The system boots from
cold in about 17 seconds (until desktop appears and the hourglass vanishes). An
8Gb compact flash drive is used for the media storage. Approx 1Gb is devoted to map
tile storage, and the remainder is available for music. The map tiles are stored as
bitmaps compressed to DXT, zipped with zlib and packed together in larger tile files.
This provides good loading performance since the tiles are in a render ready
compressed form, and low memory and hard drive usage since they are compressed.
The is a combination of an 800x600 TFT panel for the display, and a 4-wire
resistive touch screen overlay. The TFT panel is a Toshiba display LTM08C351 (I
acquired a pair for £26 from Ebay...!), hooked up directly to the motherboard
via a
PCM-3540R LVDS interface for a good quality image. The LVDS interface
allows a 10 wire interface with long signal cable capability. A TDK
CXA-P1212C-WJL inverter will be used to power the 350cd/m2 backlight.
A penmount USB touchscreen controller interfaces to the 4-wire AMT touchscreen.
The screen was molded into a dash piece bought from ebay. The screen will go
where the heater controls and central vents are, and a screen in the frontend
software will be used to replace and add to this functionality. 3 high torque
servos will be used to move the heater controls, high side drivers or relays
will control the fan and heated rear screen.
The PSU is another custom affair. Based around re-used components from the Mk2
Power Supply from the first car computer, it uses a PT6625 for the 5V supply
required for the motherboard. The optional 12V is supplied by a PT5071. This
also powers the screen backlight. Since the intended operating system is no
longer DOS, just cutting the power is not enough. A simple shutdown controller
based around a 12C508 was added to manage the soft and hard shutdown functions.
An open collector transistor presses the power button on the motherboard 15
seconds before cutting the power.
The head unit modifications are essentially identical to the ones used for the
first car computer. The switch on line from the head unit to the carputer is no
longer required and will be removed. Future plans involve using a 12C508
microcontroller to manage the switch over from radio to aux-in, to mute the
output whilst the switch occurs. This will avoid the loud thumps that can occur
with the previous setup.
The software is spread across several screens, the first of which is the GPS
screen. This gives a zoomable 2D map with the current location indicated. The
map scrolls as necessary. Datum points were placed to tie longitude/latitude,
and a delauney triangulation used to generate a mesh between those points.
Since each datum point has a grid coordinate on the map, we can use barycentric
coordinates to turn longitude and latitudes into grid coordinates to display
the correct part of the map. The padlock icon unlocks the cursor and allows
free roaming over the map by touching the map in the direction to be viewed.
The buttons to the top right allow selection of the music player functionality.
The next screen allows you to select an album to play. Touching an album entry
takes you to the play screen. The question mark button takes you to the search
page which allows you to find a specific song or artist. The list displays
album title, and where entered, the album artist. The buttons to the top right
allow selection of the GPS player functionality. The list of albums and songs
is built automatically from ID3 and similar information in the songs, and saved
in a binary format to be loaded almost instantly.
The on screen keyboard alows you to enter a search term for the music database.
The scroll window updates in real time as the search term is altered. Any songs
that contain the search term in the song title or artist name are displayed,
along with the album the song is part of. Touching any of the search results
starts playing that song from the album it lives in. To return to the search
screen from the playing screen takes just two touches of the screen, and the
search time can be refined/altered as necessary.
The playing screen lists the album being played, highlights the song currently
playing and allows you to switch to other songs. Touching the album name allows
another album to be selected. Touching an song starts playing that song. The
usual controls at the top stop, pause, play, and skip to previous and next
songs. The formats supported are limitted only by the DirectShow codecs
installed. Mp3 and Ogg Vorbis codecs are easy to find and install.