[aprssig] Car radio APRS display?

John Vause jdv at iglou.com
Mon May 18 22:29:45 EDT 2015

How about this:

I too, just bought a new(er) car in which the backup camera option was 
left off but the composite video
port is installed and accessible.

A CHIP computer along with a USB TNC or Bluetooth TNC might fit the 
bill. Or maybe a soundcard "soft" TNC.

At a price tag of $9 USD ...

On 5/18/2015 2:58 AM, KF4LVZ via aprssig wrote:
> On 2015-05-17 21:17, Stephen H. Smith via aprssig wrote:
>> On 5/17/2015 11:05 PM, Greg D via aprssig wrote:
>>> Hi folks,
>>> I recently acquired a new (to me) car, which has a Audio / Nav / etc.
>>> display
>>> unit in the dash.  The port for the backup camera is unused (no camera
>>> installed), so I was thinking it would make an interesting place to
>>> push an
>>> APRS map.  Baseband video is all that's required.  According to the
>>> manual, the
>>> reverse gear interlock can be disabled, so I should be able to select
>>> it when
>>> in motion.
>>> I was thinking the original Raspbery Pi might make for a good computer
>>> to drive
>>> it, as it is small, runs a full Linux graphical OS, has a built-in
>>> video out,
>>> and runs on minimal power.  But, what software to run, and how to
>>> control it
>>> without a QWERTY keyboard and/or mouse? There is no room on the dash
>>> or nearby
>>> to host a laptop or tablet or such, and none of the existing software
>>> I know of
>>> is car-friendly (thinking driver distractions).
>>> What I really need is something that just comes up with a map and moving
>>> icons.  Maybe a button or two for zoom in/out, one for a list of
>>> stations /
>>> messages heard, something simple for sending predefined messages
>>> back.  I'd use
>>> one of the small receive-capable "Tracker" sorts of units to provide
>>> the raw
>>> data (RF + TNC).  I don't think any of the existing "Ham HUD" sorts of
>>> units
>>> have internal maps and video out, but that would be even ideal.
>> 1)    The backup camera inputs are normally classic ANALOG 640x480
>> composite NTSC (the former US broadcast standard now used by virtually
>> nothing except CCTV cameras).   I.e. resolution equivalent to old-time
>> analog TVs or early PC CGA video output, and not remotely high enough
>> for today's GUI computer interfaces.
>> 2)    The video-out on an unadorned Raspberry Pi is HDMI DIGITAL
>> compatible with the majority of today's flat-panel monitors and digital
>> TVs. The resolution is typically either 1344x720 or 1920x1080. I.e.
>> equivalent to today's digital HDTVs.
> The Raspberry Pi's (A, B, and B-plus) all have analog video out
> available via the audio/video jack (a four-conductor TRRS jack).  The
> output format is standard NTSC suitable for any NTSC monitor so it would
> work just fine on the in-dash display.
> http://www.raspberrypi-spy.co.uk/2014/07/raspberry-pi-model-b-3-5mm-audiovideo-jack/
> The HDMI port resolution is adjustable via the configuration file in the
> root directory of the Pi.  You are not limited to the high resolution
> formats.  I have a Pi set to a much lower resolution driving an older
> VGA monitor.  It works fine.
> As for resolution in NTSC, the output is suitable for viewing rough
> icons on a modest map.  Lines marking highways and major roads would be
> fully viewable.  Small fonts may not show up very well but larger fonts
> would be readable.  Icons would need to be large enough to see or
> distinct enough to tell them apart (solid colors, basic outlines).  The
> NTSC output of a Raspi is actually respectable so using one on the rear
> view camera input is possible with reasonable results.
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