AVR-Chat

I am struggling (read: newbie) with code that will do the following, say on an ATmega 
running at 8MHz:

1. PWM for six motors (not servos) running in one direction. 6-8 bit duty cycle resolution 
is fine.
2. Sample a few sensors.
3. Receive motor speed commands via serial.
4. Send sensor readings via serial.
5. Kill all motors if no commands are received after X ms.

Seems simple but I can't determine what should be interrrupt-driven and what should be 
polled. Using timers alone for the PWM is out (I think) because I need to run six motors. 
Run the PWM frequency too high and I consume all of the cycles checking to see if a motor 
needs to be started or stopped.

Also need a serial packet protocol to frame the packets. Delay before packet? 8th bit set 
on packet header and limit it to 7-bit data? 0xAA as header and then escape it if it appears  
n the data?

Your recommendations are welcomed. Sample code would be greatly appreciated. Thank 
you in advance.

Greg Schumacher

And now we return you to your regularly scheduled thread....

> Seems simple but I can't determine what should be interrrupt-driven
> and what should be polled. Using timers alone for the PWM is out (I
> think) because I need to run six motors. Run the PWM frequency too
> high and I consume all of the cycles checking to see if a motor needs
> to be started or stopped.
Bear with me, I might not explain this well...
When I played with software PWM once, I did it as per attached code.
Basically, I use a timer to generate a master clock, on which I 
increment all the registers holding the PWM counts.  If any hit zero 
or the limit, their respecive bits are set or cleared.  Someone I 
gave the code to fairly recently had it working, I think.
 
> Also need a serial packet protocol to frame the packets. Delay before
> packet? 8th bit set on packet header and limit it to 7-bit data? 
That's how MIDI works.  I've got some code somewhere I used to decode 
some MIDI messages, I think.



Richard
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