Tv_text_demo

Celtic

On the prop demo board I have TV_TEXT_Demo
running and a NTSC tv connected to antenna input
for a try. No syncing image can be found on VHF or other.
In the program in the line
text.start(12) #12 is the base pin for TV output which is
correct for the demo-board and in TV_TEXT.SPIN I found
the line
longmove(@tv_status, @tv_params, tv_count)
in the start routine.

In TV_TEXT.SPIN tv_params data is editable.
Do I have to set up these for NTSC broadcast on VHF?

Mike Green

Yes, you have to setup the parameters for broadcast. By default, they're set up for baseband NTSC video.

Broadcast doesn't work very well. You need to set the frequency to as even a submultiple of the system clock frequency as possible and it helps if you have an antenna of the proper length for the frequency.

The best I've gotten is a range of a few inches although others have gotten better results (a couple of feet).

Celtic

This is the current setup
can you paste a copy for NTSC broadcast
setup for me to try?

DAT

tv_params long 0 'status
long 1 'enable
long 0 'pins
long %10010 'mode
long 0 'screen
long 0 'colors
long cols 'hc
long rows 'vc
long 4 'hx
long 1 'vx
long 0 'ho
long 0 'vo
long 0 'broadcast
long 0 'auralcog

Ariba

To enable TV Text for Broadcast, change the line in the start methode, which sets the tv_pin parameter to:

tv_pins := (basepin & $38) << 1 | (basepin & 4 == 4) & %0100 | (basepin & 4 <> 4) & %0001

and in the tv_params, you postet before, set the broadcast value to something like 60_000_000. This is the RF frequency of the carrier and should match to a channel of your TV. As Mike said, it works best if the frequency is a multiple of the crystal frequency.

If I put a wire (0.3 meter or so) at the TV out and a second at the RF input, it works over several meters. But the quality is not very good, a black background helps a bit.

Andy