No output to TV using TV_text and TV_terminal. Help?

Jermcb · 2011-04-08 19:15

Hi all,

I have just moved over to the propeller chip from microchip PIC's. So I am relatively new to the spin language. I have been trying to learn it and wanted to try and write text to a TV, which would be a great feature! So I connected Pins 12-14 of the propeller to an RCA jack as found a demo board.

I wrote the code below and hooked everything up, with no luck.

I have tried everything and I get no output. I checked the 3 pins on a scope and they show no output. I have tested these pins and the do turn on LED's, so they are not burnt out or anything. I tested all the pins on the chip, with a scope, to see if the TV output is being broadcast on the wrong pins like other have had problems with. but no luck.

CON

  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000


OBJ

  text : "TV_Terminal"
  

PUB main

  text.start(12)
  text.str(string("Hello World!!",13))
  repeat
    text.str(string("should work",13))

One thing I can think of is that my scope might be too slow??? (50MHz 1GS/s)
or that I used the wrong resistors, I did not have the values shown, so I 1K, 680 and 220 ohms. Is this a big problem??

or if you can spot any other mistakes, please let me know...

Any help would be appreciated!
Thanks in advance...

Rayman · 2011-04-08 19:30

Looks to me like it should work, assuming your hardware setup is correct...

Try using "fullduplexserial" along with the "Parallax Serial Terminal" and try to send data or strings to the PC.
That'll tell you if your crystall and PLL are working right...

Rayman · 2011-04-08 19:31

PS: Within the Prop tool, you can look at the "Demo Board Schematic" and see if your crystal and pin usage matches that....

davidsaunders · 2011-04-08 20:46

Using wrong resistors is not to big a deal, for this close enough seems to work well. The only thing that makes since is that the connections are not being made at all. Your scope is definitely good enough for the purpose, hook up the ground clip, and set the prob tip against P13 on your Propeller you should see a good strong signal. Also to make certain, on the DIP 40 P12 is Pin 12, and on the QFP 44 or QFN 44 P12 is Pin 13.

Lastly have you used this Propeller successfully? I am fairly sure that the chip is good, I am not so sure that it is hooked up correctly, especially in regards to the decoupling caps, remember the loader runs RCFAST clock mode, you are running with an external 5MHz crystal.

Cluso99 · 2011-04-08 22:43

Jermcb: Firstly, welcome to the prop. I am sure you will find it easy to use and this forum is a great help for information.

Now, what hardware do you have? You refer to the demo board but I am unsure if this is what you have or where you obtained the circuit.

Firstly, as suggested, ensure that your prop is working correctly by using the FullDuplexSerial object and PST (Parallax Serial Terminal). If that works then we know that your prop is working with the external xtal.

There are some settings in the TV objects that may require setting such as NTSC or PAL (the default is most likely NTSC), and some of the timings.

potatohead · 2011-04-09 00:03

I realize you are probably running the graphics_demo.spin, because it's targeted for the demo board, but have you checked the pin masks?

Jermcb · 2011-04-09 10:19

Hi Everyone,

Thank you all for your response. After trying your suggestions I noticed the chip would not use it's phased lock loop correctly. I narrowed the problem down to the power source and realized the voltage regulator I was using gave a funny saw tooth output. I switched it out and now the TV is working.

Amazing!
Thanks again!

Cluso99 · 2011-04-09 13:11

Great news jermcb. Now you can progress to all the fun things you can do with the prop

No output to TV using TV_text and TV_terminal. Help?

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