Problem with PWM on attiny84

gertc · Joined: 06 May 2006 Posts: 88

I am going to use a PWM signal for creating a DAC output. but first I have to get the PWM working. I have read most of the
forums related to PWM issues, and can't see anything wrong with the code. Tried several chips (ATTINY84A)

Here is the bare bone code: (Similar to what is shown in the help files and what others has posted)

MWS · Joined: 22 Aug 2009 Posts: 2264

Do you really believe a compare match value of 500 is suitable for an 8-bit timer with max count value of 255?
Edit:
And move setting of OCR0A in front of the loop.

albertsm · Joined: 09 Apr 2004 Posts: 5928 Location: Holland

the only thing i could find is that the data direction is not set by the compiler for portb.2 and porta.7. i did add that now.
i see in your code you set portb.2 to output manual. you need to do the same for porta.7
and as MWS says, 500 is not what you get. this will be AND-ed with 255 which will be &HF4.

gertc · Joined: 06 May 2006 Posts: 88

Stupid mistake. I changed the max count, now 200

I got it working now..... I always has the SPI cable from the STK500 connected to my board when debugging without any problem. Now, to get it working, I have to disconnect the SPI cable after programming, and then toggle the power off/on to the cpu. No Idea why.

Are there any reason that I have to set porta.7 as well? It works without doing it. (I need that extra ADC input)

thanks,
gerryc