Composite video out, digital data from outside in?
Buck Rogers
Posts: 2,185
Hello!
I've already indicated elsewhere that I am something of a naif regarding the Prop sadly. However I've looked at the code for producing NTSC video out from the Prop plus a cluster of analog components. And the one thing does come to my mind; How would I add features to it, that is the enabling of the display of user provided data?
For example I have here a BASIC Stamp2, managing the logic gadgetry that's producing it, normally it would be shown on one of the serial input LCD character displays. but with the addition of the Prop Activity Board here, I figured it could be fed to the video generation code in some fashion. And from there the output would be seen on either the TV set I have here, or on a small screen device such as this one:
http://www.adafruit.com/products/910
The reason for that screen is to make the whole business available for demonstrating the setup when a larger display isn't available. (Mine does have the composite video input connection, also left and right stereo inputs as well. To which I've got my video cassette recorder/player connected.)
Also as related elsewhere I have a Backpack on order, so without trying to work out how to run the Backpack software on it, I'd rather work with what's available.
Theoretically it would be the one of selecting an connection and making it an input, then instructing the code to retrieve data from that input.
That's where it becomes difficult. I'd rather be lost in Colossal Cave.
I've already indicated elsewhere that I am something of a naif regarding the Prop sadly. However I've looked at the code for producing NTSC video out from the Prop plus a cluster of analog components. And the one thing does come to my mind; How would I add features to it, that is the enabling of the display of user provided data?
For example I have here a BASIC Stamp2, managing the logic gadgetry that's producing it, normally it would be shown on one of the serial input LCD character displays. but with the addition of the Prop Activity Board here, I figured it could be fed to the video generation code in some fashion. And from there the output would be seen on either the TV set I have here, or on a small screen device such as this one:
http://www.adafruit.com/products/910
The reason for that screen is to make the whole business available for demonstrating the setup when a larger display isn't available. (Mine does have the composite video input connection, also left and right stereo inputs as well. To which I've got my video cassette recorder/player connected.)
Also as related elsewhere I have a Backpack on order, so without trying to work out how to run the Backpack software on it, I'd rather work with what's available.
Theoretically it would be the one of selecting an connection and making it an input, then instructing the code to retrieve data from that input.
That's where it becomes difficult. I'd rather be lost in Colossal Cave.
Comments
If you only have data to get from the BS2 to a Propeller, you could use a serial link between the two, and output NTSC data from the Prop with four resistors base on the Demo Board Schematic:
http://www.parallax.com/sites/default/files/downloads/32100-Propeller-Demo-Board-Schematic-RevG_0.pdf
No need to use the Backpack unless you are going to overlay BS2 info directly to the video.
+1
That's the way I usually do it. You don't have as much freedom to select pins as usual. I think the video pins need to start on the first of a group of four pins. 0, 3, 7, etc.. I just keep my pins the same as the Demo Boards so I don't have to fuss with changing the driver.
The Backpack code is a great example of how to use the Propeller as a display for other microcontrollers. The protocol does take a bit to learn, but Phil has done his usual great job at documenting how it's done.
If you're going to use the Prop for other stuff besides just displaying video, be aware that video is a memory hog. There's a cool little demo for an accelerometer which outputs a rotated cube on video display. I tried to add a few extra features to the demo and soon ran out of memory. I think there are tricks to reduce the memory used but they're not obvious (to me at least).
Hello!
Actually that is the next step. The code used, (and currently being debugged) will be directly sending things to the Backpack that way. However I'm still stuck on the subject of including that data in the form being sent to the Prop.
And yes I did look briefly at the demo code for both the accelerometer and the gyro. However I never got around to trying the code for the gyro with a Prop.
Is there a method as to how to include serial data traveling from the stamp and into the Prop, using the original ideas presented to the OBEX for preparing video display methods?
Next up: Building the video generation stage on the PAB and testing the code I have on a screen.
Thanks guys.
BTW you can also use the reversing camera displays from eBay - they are larger than the one you linked to, but they are fully enclosed. Were ~$25 on eBay.
Hello!
It happens that the Backpack I, ah, ordered, so this whole one has become moot. But it is still full of good ideas. I'll consider your idea concerning those screens.