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Hello,

I'd like to know if it's possible to increase the numbers of colors by using PWM method to generate R, G and B signals.
I use a XyloEM card.
The problem is I need to use the highest clock (48 MHz) but I don't know if it's enough to create new colors. Moreover I don't know if my screen will "average" the signal...

Thanks for answers !

Antoine

Most monitors are much faster than that and pwm will make a pattern instead of different levels. I have run 50 MHz on very old VGA monitors and even then there is no hope of using PWM.

Your best bet might be to use the colours you got and find the error from the colour you want and add that to the next pixel. It will give the correct colour on average and if the residual error is passed to the next frame too you get an average over time. This is an old trick to display photographs on computers with only 256 colours.

8 colours is not enough to get a good display unless the frequency is extremely high, with 256 colours you can begin approximate a 24 bit display.

You probably need to add a 3x4 bit R-2R D/A circuit to get a really nice display.

Ok, thanks for your answer.
That's what I thought...
Your "old trick" seems great ! I'll try it !

And the 3x4bit R-2R DAC is a good solution but I need to use a different VGA plug with other pins on my board...

Is there a solution to display more colours with the embedded VGA pins of the Xylo EM ?

I think PWM is your best bet. It may create a pattern at closeup though.

Ok, thanks, I'll try it !

I saw a project on the net that used the floating state of the pin to increase the number of values. I think it also required an additional resistor and a diode