[aprssig] APRS in-dash display

Mark Cheavens mcheavens at usa.net
Sun Jan 17 17:37:26 EST 2016

You have not said what make model of car, so I have no idea if I have 
any experience with it.

- Other comment from someone else about A and B models only have 
composite video, that is not true. The later models (B+ have it, but did 
not poplulate the connector).

On 1/17/2016 1:49 PM, Greg D via aprssig wrote:
> Hi Lee, all,
> Yes, sorry.  Typo...  The Pi has a built-in baseband 640x480 video 
> (aka RCA) output, so I won't need the adapter box.
> I'm expecting to run the video through a simple SPDT switch to select 
> either the Pi or backup camera.  If I get fancy, maybe tie that to the 
> car's backup signal and use a relay to switch automatically.  No need 
> or intention to sacrifice one for the other.
> My expectation is that the system will be on RF primarily, though I 
> haven't located a good place for the antenna.  I was initially 
> thinking to use a small bi-directional tracker-like module (Rx and TX 
> required), but will probably start with my Kenwood D7.  If I can do 
> tethering with my cell phone, I might be on IS too.
> The Accessory outlet does remain on for several minutes after parking, 
> but I really need to have something that's automatic because I'd 
> likely forget.  So, either I make the Pi's file system read-only (so 
> it doesn't care about abrubt loss of power), or trigger the shutdown 
> automatically.  My thought is to put a small 5v NiCd battery on the 5v 
> input rail, to hold the Pi running for a bit, and trigger a shutdown 
> when the +12 input goes away.  I'm not very familiar with the Pi yet, 
> so perhaps it has a low power suspend mode, where a small battery 
> could hold it for a couple of weeks.  That would probably be ideal, 
> though I'd still need to trigger the state changes.  Haven't had a 
> chance to investigate this, beyond recognizing that the issue exists, 
> at least in theory.  Am I over-designing this?
> On the topic of the operator control, perhaps instead of switches and 
> GPIO pins, I recalled after my posting that some cars have essentially 
> a joystick mouse-like control mounted between the seats.  I'm not sure 
> how well this would work on the small screen, but that might solve the 
> problem.  Anybody have one of these cars, and could relate how it works?
> Greg  KO6TH
> Lee Bengston via aprssig wrote:
>> On Jan 17, 2016 12:24 AM, "Greg D via aprssig" <aprssig at tapr.org 
>> <mailto:aprssig at tapr.org>> wrote:
>> >
>> > Hi folks,
>> >
>> > Picking up on a thread I started a while back...  Not sure if this 
>> will lead to something permanent or not, but I tought I'd give it a try.
>> >
>> > I got access to the back of my car's in-dash unit, and the video 
>> input connector.  It's meant for use with a back camera, which I 
>> currently don't have (though it's on the wish list...).  Found a VGA 
>> to RCA adapter box, and fired up APRSIS32 which was loaded on a small 
>> laptop.  Here's the result:
>> >
>> > http://home.wavecable.com/~ko6th/aprs_dash_display.jpg 
>> <http://home.wavecable.com/%7Eko6th/aprs_dash_display.jpg>
>> > http://home.wavecable.com/~ko6th/aprs_laptop.jpg 
>> <http://home.wavecable.com/%7Eko6th/aprs_laptop.jpg>
>> >
>> > Given the difficulty, if not questionable legality, of controlling 
>> a GUI-based laptop while driving, I think the next steps need to include:
>> >
>> > 1.  Replace the laptop and VGA adapter with a Raspberry Pi.  VGA 
>> output is built-in, also much better power draw and small size. (The 
>> car is a sports car, so no room for anything bigger.)
>> I think you meant RCA is built in, right?
>> > 2.  Replace APRSIS32 with YAAC (for Raspberry Pi compatiblity).
>> >
>> > 3.  Probably still need a keyboard for full control while parked, 
>> but add some fixed key switches tied to keyboard shortcuts for the 
>> common stuff while driving.  During the earlier exchange, Andrew 
>> figured it was a "simple" matter of a Java library to bridge the 
>> swtiches to keyboard shortcuts... Hope he's right.
>> >
>> > 4.  The Pi will boot itself when the car turns on, but I need a way 
>> to automatically safely power down the Pi when I turn the car off. 
>> Any ideas on this?
>> >
>> A lot of vehicles don't shut the radio off immediately - will 
>> eventually time out - and many will shut off once you open the door.  
>> You could source the power from a source that doesn't shut off right 
>> away and buy yourself time to shut down gracefully.
>> Sounds like fun - my truck has a backup camera that I would not want 
>> to be without.  :-)
>> Lee - K5DAT
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