PIC speed problems

[skimask]

Its a PIC16F87. From what i can see it only has 2 PWM outputs. I need 4. Good idea though. I never thought of that. Maybe if there is another 18pin PIC with 4 PWM outputs then i can use it

Or, you could look up Slow Speed software based PWM and get almost as many channels of PWM for messing with LEDs as your PIC can handle.
I've been able to do 20 RGB LEDs (3 colors each of course) at 152.5Hz (way fast enough to prevent flickering), serial data input/output (using the PIC's hardware modules), key pad scanning, reading an eeprom, housekeeping chores, etc. all using a software PWM scheme based off Timer 0. Works like a champ, no flickering, etc.etc. That's with an 18F at 40Mhz. Use a 16F at 20Mhz, and you'll still be able to get 76.2Hz (again, fast enough to prevent flicker) and still be able to drive a load of software based PWM outputs on an 18pin PIC.

[The Master]

Ok, ill have a look around for it. Im using a 20MHz oscillator already. The baud rate for the serial data is 115200. I would have thought that uses more processing power but i did have this working earlier. The problem seems to be with the code between the serial data arriving and the LEDs being turned on. Im still cutting as much out as possible but theres a limit to how small a program can be before it doesnt do everything you want. Ill probs strip my program back to basics when i test out that software PWM thing then build it up a few lines at a time.

[skimask]

You're using an 'F87, I used an 'F628A. 15 I/O pins available for me, 2 used for 20Mhz crystal, 2 used for Serial I/O, PGM/MCLR tied as needed, 3 buttons and 6 LEDs (2 RGB), and one spare pin. I was able to do serial at 19,200 without a problem using the hardware module (datasheet says it's 1.7% high, but it worked). Used Timer0 kicking an overflow interrupt at 19.531khz, software PWM for each LED at 76.2Hz, 8 bit resolution. Could get a higher refresh rate at the expense of resolution. Once in a great while, I'd get a slight bit of one-time flicker if I was trying to receive serial data too fast or send it too fast, but that's completely up to the software driving it.
I think that 'looping' PWM will end up kicking your butt in the long run, but that's just me.
Time to learn how to use interrupts to your advantage!

[The Master]

I found that PWM thing. Took a bit to get it working (installing MPASM etc) but i figured all that out. The problem i have is that for some reason the serial interrupt, PIR1.5, never equals 1. Im not sure whats wrong. At first i thought maybe the loop wasnt running but i added code to increase/decrease the PWM value and it worked fine. Its just that interrupt that doesnt seem to work. Im guessing its got something to do with the timer interrupt overriding it or something.

Edit: Im not using ON INTERRUPT. Aparently that doesnt work. Im only checking for PIR1.5

[skimask]

Edit: Im not using ON INTERRUPT. Aparently that doesnt work. Im only checking for PIR1.5

I'm using the ON INTERRUPT in that particular program I eluded to earlier. Works fine for me. It's definitely not optimal like the Instant Interrupt's, but it works and it would take too much rework to change it over.

If you're serial isn't working, get rid of the PWM for awhile and just turn things on/off to show that the serial port is in fact working (or not). Again, break it up...then put it back together...

[The Master]

The serial was working fine before and still does work with test programs. It only stops working when i add the PWM code. I tried adding the PWM code to an existing program that i know works. The PWM works fine but stops the serial from working. I also tried a brand new program starting with just the PWM and adding serial but with the same results.

I cant seem to send data while the PWM code is in either. Its like its overriding the settings for things like continuous receive etc and disabling serial.

Would it be worth trying to write code to use the timer similar to this PWM code but writing it in PBP instead of ASM? I dont understand ASM at all so when something goes wrong i have no idea how to fix it. Is there something like PIR1.5 but for the timer instead? Would that work or would it run too slow?

Edit: I have some code to turn a status LED on for about half a second whenever PIR1.5 equals 1 regardless of the data i get from RCREG. Always works without PWM but never works with it. I also had a blank project with only PWM and some simple serial receive code that copies RCREG directly to one of the PWM values but still no luck

[skimask]

Ok, just to be on the same page here...
When you say 'PWM' code, what do you mean exactly?
Something tells me that you're using the 'PWM' command and not the hardware, or even an interrupt based PWM method...