random and LEds question

[Jowkar]

how do i make LEDs less bright, i know that u need to do something with the PWM and how to generate a randon number in vhdl




also how do i search in the newsgroup

 

[jeppe]

Your quite right - a PWM output will be perfect in order to control a LED brigthness.

Try this link for more information: http://www.jjmk.dk/MMMI/Exercises/05_Counters_Shreg/No7_PWM_vs_SigmaDelta/index.htm

Your welcome
Jeppe

 

[jeppe]

One more

1) Search for LFSR at the net - could be perfect for random numbers
2) Use a fast running counter - the number will be random if you stop the counter with random intervals.

 

[Jowkar]

thanks, i think i got the random numbers going, i did the counter thing, but the pwm thing im still not too sure, im using a spartan 3 and im kinda new to vhdl so i dont know where motors and stuff are located on spartan 3

 

[jeppe]

Depend on your kit or hardware design
Most pins on a Spartan 3 could act as output and hence should it be possible to drive with a PWM signal

 

[Jowkar]

i figured most stuff out, what i still dont really quite understand is the PCM value, can anyone elaborate on that?

 

[jeppe]

PCM = Pulse Code Modulated which means a number, value etc which gives the PWM percentance. If you a kit (BASYS, NEXYS etc) could you use the DIP switches to generate numbers like 00001100 = 12 or 10000001 = 129

 

[Jowkar]

what i meant is, how does the pcm value affects it like the higher the what and stuff

 

[jeppe]

Well if you watch the simulation (buttom of the page link) can you see the connection between PCM and PWM
If you decide PCM=15 => 100% duty cycle (Full brightness) then PCM=7 should give say 50% duty cycle