Multiple PWM outputs

Guest · Posted: Wed Nov 12, 2003 2:51 am

Hello,

I need 4 PWM outputs and found that the 18F448 has 5.

How do I setup this use of 4 PWM's for 10 bit output ?

Are the duty cycle's independent of another ?

How do I set duty cycle for each PWM ?

Kind regards,

Gerrit

Ttelmah · Guest

dazlogan · Joined: 19 Oct 2003 Posts: 24 Location: Cambridge, UK

couldn't you use a timer to control 4 pins high/low - the high/low times being controlled by a counter variable?

i.e. make your own PWM???

only trouble is, will this be accurate?

i guess the timer interrupt would need to be top priority.

regards,
darren

Guest · Posted: Wed Jul 19, 2006 5:39 pm

MGP · Joined: 11 Sep 2003 Posts: 57

This is a little off-topic, but I wish Microchip would spiff up their peripheral mix a bit and add more hardware PWM channels to a few PICs, especially in the 18F family. I know they have added some features to the dsPIC and PIC24 family, but those PICs all require a whole new toolset and aren't pin compatible with the smaller PICs.

I've been doing a lot of MSP430 designs lately and the bigger MSP430's have some really excellent peripherals. For example, my last design used an MSP430F44x part that used 160 (4x40) LCD segments, 2 hardware UARTS, six 12-bit A/D channels and 6 hardware PWM channels (Timer B). It also used two CCP (input capture, Timer A) channels. If you are willing to give up a UART, you can get either hardware SPI or I2C. You can get all the same peripheral mix minus the LCD driver in the MSP430F14x family. There aren't ANY PICs that even come close to being able to do all that in hardware. TI has done a very good job, IMO, of picking the mix of peripherals to include on their parts.