[aprssig] Car radio APRS display?

Greg D ko6th.greg at gmail.com
Mon May 18 01:49:05 CDT 2015


Stephen H. Smith 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.
>
> 3)    The one use I have toyed with for the analog composite input of 
> these dashboard displays (even my Garmin Nuvi 855 has one) is as a 
> live monitor for my mobile "SSTV LiveCAM" setup.   Here I feed an NTSC 
> composite camera signal into the composite input of the Kenwood VC-H1 
> handheld SSTV device's scan converter where one NTSC fastscan frame is 
> grabbed and down-converted to a Single SSTV image.  It would be nice 
> to have a live "viewfinder" display for this setup.
>
> Currently I use a Canon Powershot A520 point&shoot digicam. This 
> camera has an NTSC composite analog output intended for playback 
> picture display on analog TVs of the day (15 years ago) that had the 
> yellow RCA composite-in video jack.   The Powershot's own camera-back 
> display functions as a view-finder but it's small (1.8"). I would 
> really like to use a decent zoom-tilt-swivel CCTV camera that runs on 
> 12VDC, and use the dashboard display as it's viewfinder.
>
> ______________________________________________
>
Hi Steven,

The dash unit displays the navigation maps satisfactorily, and that's 
all I am expecting from this project.  Not the best, but given the 
limitations of the platform, probably all I can hope for.

I understand that the Pi has an HDMI output, but I believe there is also 
an NTSC "RCA" video out.  At least, on the older Pi.  They may have 
dropped it from the new one, or moved it to a header.  As long as you 
don't use the HDMI, the display squirts out the RCA port. So, I think 
this should work.  Again, I'm not planning to run a full X-windows GUI 
environment, as even if it would display, the control via QWERTY 
keyboard and Mouse is impractical and dangerous in a moving car.  I need 
a simple map display (similar to the Garmin, et al), and some buttons.

One possible direction to follow would be the YAAC application, which 
sounds promising.

Ah, and thanks for the reminder about the older digital cameras.  I have 
a PowerShot S-30 in a box somewhere that I could use for testing.

73,

Greg  KO6TH






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