Optimal Portable Tv for Prop?
Keith Young
Posts: 569
I am looking for the best specs for a portable tv to run with the Prop. I would like to be able to display useful information for FPV flying, which would include camera with HUD overlay and maybe some indicators.
I'm not seeing in the documentation what resolution is supported. I also don't have a feel for how small of a screen will still give a fairly good picture with enough information on it. I know it needs to be NTSC but other than that I don't know what to look for when mating to Prop.
Not related to Prop, I want it to plug into a wall, cigarrette lighter, and preferably also have battery. My guess is 7" should be enough.
At the moment I am looking at this http://www.amazon.com/Haier-HLT71-7-Inch-Handheld-LCD/dp/tech-data/B001E78UQY/ref=de_a_smtd
Any better suggestions? Especially relating to Resolution. I don't know if Prop can drive 720p. I assume I could arrange for sound to go through 2 more VGA plugs.
I'm not seeing in the documentation what resolution is supported. I also don't have a feel for how small of a screen will still give a fairly good picture with enough information on it. I know it needs to be NTSC but other than that I don't know what to look for when mating to Prop.
Not related to Prop, I want it to plug into a wall, cigarrette lighter, and preferably also have battery. My guess is 7" should be enough.
At the moment I am looking at this http://www.amazon.com/Haier-HLT71-7-Inch-Handheld-LCD/dp/tech-data/B001E78UQY/ref=de_a_smtd
Any better suggestions? Especially relating to Resolution. I don't know if Prop can drive 720p. I assume I could arrange for sound to go through 2 more VGA plugs.
Comments
Most programs use a 40 character x 13 line NTSC screen resolution. I've used the Axion unit with the 8 x 8 pixel font driver that's in the Object Exchange and I get over 64 characters width and 25 lines of text (If I remember correctly). Graphics is limited by the amount of Propeller memory available for a bitmap buffer rather than the screen's resolution.
Have a look at the TV drivers in the Object Exchange for ideas on what's possible. Also look at the documentation for the Propeller Backpack for an idea of what's possible with video overlays.
Sound depends on the board you're using. The Demo Board has a stereo headphone output. Most other boards have monaural line level output. You can always add another channel if you have a free I/O pin.
Another option is a portable USB capture device. Those can display Propeller TV output right on your computer desktop. I use one of these fairly regularly.
I have on of these its works good for TV to PC veiwing.
http://cgi.ebay.com/EASYCAP-USB-2-0-VIDEO-AUDIO-TV-VHS-DVD-CAPTURE-ADAPTER-/250678363892?pt=LH_DefaultDomain_0&hash=item3a5d9846f4
There are also some under $15 units out there, typically called "EZ-CAPTURE" or something similar. OBC found these, and I snagged one right after he did, just because the price was good. These are regular definition devices. Their signal processing isn't quite as good as the HD ones seem to be, but for most purposes they will work great. I have one of each. These devices break down at 80 columns, rendering 64 columns tolerably, but really are good for 40 column text on NTSC TV's. They do have S-video outputs and that helps considerably, but that does require Propeller S-Video capable drivers. I did a test once, and that's it. Looked good, but I really didn't qualify it. It's easy to just use composite, or VGA.
Either one will display nearly all the stuff we have written to date, with the exception of the higher density text and tile drivers. HD devices can do color 640 pixel displays on TV with enough clarity to work with, which is impressive, on a composite signal. SD capable ones will perform the same at 320 pixels resolution. The inexpensive one comes with lesser quality software. I find it more clunky, but totally usable. That's what I'm running right now actually. I just leave the video preview window up, and use the windows "alt+tab" to go back and forth between video output and my programming IDE. (prop tool, at present) The ADS software can be minimized to a small window and parked in the corner of the screen. I like that, but it's again, price. The ADS ran me $80, and I think they can be had for maybe $50 on a deal.
For the price, it's hard for me to recommend the more expensive HD devices, given most of the propeller TV output is 320 pixels or less. Go for the cheap one, and you will be fine. I got one as a backup, and I use it regularly on a Vista computer that doesn't want to play well with the ADS software. (See my blog, Windows 7 will work though)
All in all, these rock. I do prop programming on business trips, where it's the hotel room. Might as well. Also makes for a pretty small dev area at home too. Fire up the software, and use the video display / preview window to see what the Prop is doing. Both software packages can capture frames and or a movie. I use the movie once in a while to debug something I find hard to see without slo-mo capability. Otherwise, I just capture frames when I need to.
The only real downside I've experienced is there is a latency between the screen image and what the Propeller is doing. Typically this is about 2-300ms, up to a full second, depending on the software and how it performs on your particular graphics system.
Non issue, but for gaming, or testing things that you interact with. Text input works well though. The latency isn't a bother. This latency is due to the signal buffering required by the OS.
I've not used the DVD recording specific ones. I think the "EZ-CAPTURE" type devices are built for that, because they don't have a TV tuner in them. The ADS device was clearly meant to deliver HDTV on the go, and it does. Comes with a little tiny magnetic mount antenna. Where I live, I can get 20 channels on the thing, with maybe 5 of those featuring good programming. Was kind of impressive. Once or twice, during election times, I put the antenna on the car roof and listened to TV audio while driving too. Again, I was kind of shocked at how well that really did work.
Google for either "ADS HDTV USB", or "EZ-CAPTURE" and you will find your way to one of the devices. Be sure and select one with Windows 7 / vista support. That kind of goes without saying right now. IMHO, the SD capable devices should work well under Linux. I doubt the ADS device will. It appears to be very specialized in how it works. Their software, or nothing. So just be aware of that. Maybe their newer ones are different. I've had mine for a long time now. Picked up the ADS a coupla months after catching the Propeller fever in 2006? Maybe 2007? Can't remember, and I'm not gonna search. It's just been a while.
I'll try and find the thread on the old forum where I did a capture with both.
http://forums.parallax.com/showthread.php?115735-Most-expensive-Propeller-addon-yet..&p=846383&viewfull=1#post846383
The new search is awesome. Just for grins, I made a luma / color cable. That's a S-video cable on one end, two RCA jacks on the other. I've attached a capture of the cheaper device, running S-video luma only to show what that's like.
Potatohead: Thanks for this great information and for taking the time to provide this level and wealth of useful information! It also alerts me to the fact of special software that comes with the device will be language oriented. So likely while traveling in China, the device purchased could be packaged with a Chinese language software version which would be a bit daunting to use (Chinese language is highly indirect when it comes to technology). So with this knowledge I can look for some dual software language package. I'm rather excited about getting one of these because the large TV is permanently mounted on the side wall in the Chinese apartment is not movable and the tiny NTSC monitor is a bit small with a 3.5-inch screen. The computer as a TV would be a good solution, and for more portability I can use a Netbook like the ASUS EEE PC if the software runs on that version of Windows. I could probably do without the tuner function since this would be a prop tv to computer function use.
As for the software, I'm quite sure the website offers various downloads. Most core software is internationalized these days. Probably it's just a matter of finding the right package.
Taken next to PPDB for size reference. This is the TV from OP.
I'm currently using one of these:
http://www.tigerdirect.com/applications/searchtools/item-Details.asp?EdpNo=612720&sku=O38-1022
and I'm pretty happy with it. The cheap one I bought off ebay had issues with color.
OBC
I don't know your space requirements but there is a large area about 3/8" deep, especially if you are willing to remove the RF unit. To make more use of space you may need to relocate the Capacitors and use thin wire leads if your board has a large footprint.
With all the little surface mount resistors and all that I'd say its safe to fit in a 1/4". For reference the large IC in the middle is about .06" above the Green PCB. It's higher than the resistors.
8 Sm Phillips all same size, then looks like 4 Med Phillips all same size to get below the Green PCB. At a glance RF module looks fairly easy to remove.
Plastic cover is a rubbery plastic so this is probably pretty durable.
USB apears to be for firmware updates.
Battery is labeled as 2000mAh 3.7V
Wall wart 9V 2A. Car plug 12V 2A.
Screen seems to take power leads and a small ribbon cord.
The TV graphics have a "safe zone", based on the fact that not all display devices will render the entire frame. Inside of that is the "active" graphics area, or "safe" area. Outside that is typically, "the border", or "overscan", and isn't always used.
Some objects can use more of the screen. The Parallax one you fired up can, by changing the parameters associated with the TV object, and or changing the number of tiles in the display.