any example to use PWM control for PIC16F877A

artohautala · Joined: 17 Nov 2011 Posts: 187

Hello,

I want to use PIC16F877A pin C2 to control the brightness of the backround light of LCD display... with pulse width modulation.
I have FET connected to pin C2 and on/off control works fine.

Is there any example how to use PWM module for that purpose ?

I understand how pulse width modulation works in theory but I had no success to get it work though I tried it make to work in many ways ...
if you want please help me ...

I do not understand this ccs manual good example how to use it:

asmboy · Joined: 20 Nov 2007 Posts: 2128 Location: albany ny

you need to:
** setup timer 2 for frequency control

and then
** setup the pwm module for PWM output
per the ccs manual

CCS compiler will handle the TRIS for you

look at MR.T's code in this post

http://www.ccsinfo.com/forum/viewtopic.php?t=51167&highlight=pwm+setup

artohautala · Joined: 17 Nov 2011 Posts: 187

asmboy · Joined: 20 Nov 2007 Posts: 2128 Location: albany ny

see figure 2 for a block diagram of a useful circuit

http://www.electronicsnews.com.au/features/power-converters-stretch-battery-budget

artohautala · Joined: 17 Nov 2011 Posts: 187

asmboy · Joined: 20 Nov 2007 Posts: 2128 Location: albany ny

fig 2 is a simple block diagram of a buck modulator

which is a classic way to use PWM for adjusting the output power of a fixed supply. with a 5V dc input - substitute a P channel FET for the transistor, and direct drive the gate with the PIC PWM Output to vary the power sent to an LED back light and your problem is solved.