Arduino as PAL video generator, software question

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PA3CRX
Posts: 13
Joined: Fri May 24, 2013 8:38 am

Arduino as PAL video generator, software question

Post by PA3CRX » Tue Apr 07, 2020 11:57 am

Since video consists of sinq pulses, a black level and a white level for white, this can be done with an arduino.
The gate that makes the pulses with a different voltage divider than the gate that makes the white level by means of two resistors. (Bottom sinq: 0V, black 0.3V, white 1V).
The information and the sketch can be found at https://playground.arduino.cc/Main/TVout
With little effort it is possible to find out how, for example, a call or other text can be displayed.

Code:
#include <TVout.h>
TVout TV;
unsigned char x,y;
void setup() {
x=0;
y=0;
TV.start_render(_PAL);
}
void loop() {

TV.print_str(40,16,"PA3CRX");

TV.print_str(50,32,"ATV");

}
arduino_generated_call.png
arduino_generated_call.png (49.92 KiB) Viewed 1302 times
However, the characters are relatively small. They are built up in the following way (for example the letter "P"):
Code:
//P
0b11110000,
0b10001000,
0b11110000,
0b10000000,
0b10000000,
0b10000000,
0b00000000,

So it seems a little effort to make large characters for this but I do not know how.
The intention is to equip my portable stations with an Arduino with, for example, the number code that is broadcast during the ATV activities weekends. This code can then be displayed without having to connect (separate) peripherals.

I came across a URL that should make it possible to display a logo, for example. (https://www.open-electronics.org/a-vide ... r-arduino/)

With a tool mentioned herein, for example, in Paint a call or numbers can be converted to Ascii and that could be displayed. This is indeed not a problem. However, I am unable to adjust the sketch in a way that it works.

So my question is whether someone has something like this working (or someone with a knowledgeable interest who is interested in making something like that) and then want to share the information about it.

Thanks in advance,
Chris PA3CRX

radiogareth
Posts: 507
Joined: Wed Jan 06, 2016 9:46 am

Re: Arduino as PAL video generator, software question

Post by radiogareth » Tue Apr 07, 2020 1:00 pm

If I remember correctly PICDREAM did something similar. Not complex, but useful. I think its software is in the BATC somewhere. I remember building one 20+ years ago!
Gareth G4XAT

G4FRE
Posts: 117
Joined: Fri May 26, 2017 6:57 am

Re: Arduino as PAL video generator, software question

Post by G4FRE » Tue Apr 07, 2020 1:15 pm

I still use its successor PICDREAM 2 after getting some PCB made. Its even more useful now i can change messages etc from my cellphone "in the field"

The only issue is (as Noel has experienced) if you feed it 's output into the composite input of the portsdown it gets transmitted with the top 5t0% of the testcard at the bottom of the received image and the bottom 50% of the testcard at the top of the received image. Looks fine directly on a composite monitor though

Dave
G4FRE

PA3CRX
Posts: 13
Joined: Fri May 24, 2013 8:38 am

Re: Arduino as PAL video generator, software question

Post by PA3CRX » Wed Apr 08, 2020 7:14 am

Thanks for reply and the suggestions.

However, to generate simple video is more easy with Arduino, only the cheap arduino is needed and two resistors (for the video levels). And it is a small thing, could easily be fitted in the housing with the portable (analogue) transmitter.

The only point is I do not have enough knowledge about the sketch to make the characters larger.
Making the matrix with more pixels like cq-tv267 page 32 (Turning back the pages of CQ-TV 78) is not the problem (like the letter ‘P’, as in the example above). But what needs to be changed to make it appear?

Thanks in advance,
Chris PA3CRX

PA1KW
Posts: 16
Joined: Tue Dec 17, 2013 9:27 pm

Re: Arduino as PAL video generator, software question

Post by PA1KW » Thu Apr 16, 2020 7:58 pm

Hi Chris,

I was also looking for a such a solution and was working on a chipset from VLSI, but did not had time to complete it yet. On hackaday there is an example:
https://hackaday.io/project/21097-ntscp ... lay-shield

A lot of info about the chip on:
http://www.vsdsp-forum.com/phpbb/viewforum.php?f=14

To generate image and fonts you can use this application:
http://www.eran.io/the-dot-factory-an-l ... generator/
Not sure you can use it with your solution as well.

I'm happy to test as well and see if we can get it to work.

73 Koert PA1KW

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