Reworking your ideas

[uditrana]

I have bought your board and really enjoyed using it. But then for a lab at my college I wanted to take it further and turn it into a project.

I took Lady Ada’s DC Boarduino and added RCA Output (and VGA but that was already there) for Audio and Video to it. I am using a Atmega 328p and the goal was to have 8 buttons (4 for D-Pad and 4 for ABXY) and let the students mess with it and code for it. Actually really similar stuff that you have coded.

Anyways I have designed and printed a proto-board and got it all soldered up but TVout refuses to work. Right now I am just messing with video and as per the schematic on the TVout page it SHOULD work. Now I am trying to figure out why it worked on the HackVision and not my board.

After comparing it seems to be that you guys did something different for your resistors on the Video and Sync using a 75, 1K, and 330. Can you explain why?

I have uploaded the zip for eagle files and gerbers for my board. I am also having trouble with some code for some reason but that’s a different issue.

[Michael]

I don’t understand your design. Are you trying to do VGA or Composite video using TVOut?
TVOut generates the signal on digital pins 7 and 9. You don’t even have those pins connected in your design. How did you expect it to work if you didn’t connect the pins?

I just followed the design that the TVout guy proposed, except used a 330 ohm instead of a 470 ohm. I also put a diode on each line. The 75 ohm resistor is generally not needed because there is 75 ohms of resistance in the TV between the composite input and ground.

The details of how to use TVOut are here: http://code.google.com/p/arduino-tvout/

[uditrana]

OK I am extremely sorry, as I forgot to mention some things. The goal was to have both VGA and Composite Outputs working. The VGA uses something that is not TVout (designed by Nick Gammon) and has a 9th bit issue that causes white bars on the way down. I knew how to get VGA working (based on a previous protoype) and so hooked those up through the PCB. That works BUT I could never get the composite to work (using TVout) and so didn’t connect it through the PCB left BUT have left space on the board to wire things up from above. I tried the design that the TVout guy proposed and tried to get sample code they provide to work. Their code compiles, uploads, but nothing shows up on the screen.

I will try switching the resistor over to a 330 ohm.

ALSO I tried to make some simple code that just displays text (instead of the complicated rotating cube and etc. they provided) but for some reason it refuses to compile.

I have attached a screenshot, it claims that some functions are not part of the libraries I think but some other people tried similar things and it worked.

[Michael]

I don’t know where you got that code, but it’s just wrong. There is no start_render or print_str methods in the API.
Download the most current TVout from the web site and look at the examples and the API.

[uditrana]

Really wow. Ok I got it from a rather Dated source. Ok sorry about that.

Ill fix that and try to use their example code again

[uditrana]

Wow thanks Michael. Using a 330 Ohm Resistor fixed the video out issues that the board with 470 was having. Demo NTSC works.

Now I have to get audio working and test it with code but more importantly remap some existing games (tetris from TVout, and maybe your asteroids) to try to work with my button layout.

Any tips/cautions moving forward on trying to get the games working?

I have attached a picture of the board

[Michael]

I think you’ll have no problem adapting the games to different pins for the buttons. Just look at the code, you can do it.

[uditrana]

Thanks, I’m working on it.

Couple of questions?:

Any particular reason you put a diode through to the RCA? Is it worth adding?
And I noticed you didnt have pull-up resistors on the buttons, and I know that the pins on the MC feature internal pull-ups but sometimes they dont work well. Have you found them to be reliable enough to forgo the manual pull-up?

I am really trying to minimize board space so wondering if the Diodes and the manual pull-ups (Just in Case) is necessary

[Michael]

The diodes prevent current from flowing from one pin to another. You have two pins generating signals and you are tying them together. If one pin is HIGH and the other LOW, then the LOW pin will sink current from the HIGH pin. Diodes are a good idea.

You don’t need pullup resistors on digital inputs if you use the internal pullups. I’m not sure why the internal pullups would not be sufficient.

[uditrana]

That sounds good, I have added diodes to my board.

Also I’ll be adding Nootropic Design in my acknowledgments in our engineering paper and presentation because of your significant contributions to this project. We used the 330 ohm resistor, the diodes to RCA, and we will be adapting your games for our board.

Thanks!

[Author]

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