Skip to content

Commit

Permalink
Example: use delayMicroseconds()
Browse files Browse the repository at this point in the history 
This greatly simplifies the code and reduces the compile size.
  • Loading branch information
@per1234
per1234 committed Dec 23, 2015
1 parent 8b97eda commit 5104017
Showing 1 changed file with 2 additions and 6 deletions.
8 changes: 2 additions & 6 deletions examples/PalatisSoftPWM_example/PalatisSoftPWM_example.ino
View file
Original file line number Diff line number Diff line change
Expand Up @@ -85,16 +85,12 @@ void loop() {
Serial.print(" loop(): ");
Serial.println(i);

unsigned long const WAIT = 1000000 / SoftPWM.brightnessLevels() / 2;
unsigned long nextMicros = 0;
for (byte v = 0; v < SoftPWM.brightnessLevels() - 1; ++v) {
while (micros() < nextMicros);
nextMicros = micros() + WAIT;
delayMicroseconds(1000000 / SoftPWM.brightnessLevels() / 2);
SoftPWM.set(i, v);
}
for (int v = SoftPWM.brightnessLevels() - 1; v >= 0; --v) {
while (micros() < nextMicros);
nextMicros = micros() + WAIT;
delayMicroseconds(1000000 / SoftPWM.brightnessLevels() / 2);
SoftPWM.set(i, v);
}
}
Expand Down

5 comments on commit 5104017

@Palatis
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

the original "intention" for using while loop instead of delay() or delayMicroseconds() is to demostrate that the SoftPWM library doesn't block the loop(), so users can run their own codes.

but assume every arduino players SHOULD know that delayMicroseconds() is a busy-waiting loop, these two should be considered equally instructive.

@per1234
Copy link
Owner Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

@Palatis thanks so much for taking a look at my code. I hope you don't mind that I have made some changes in my fork. If you see anything I've done you would be interested in merging to your repository I'd be happy to submit a pull request. I have been meaning to do one for my SOFTPWM_DEFINE_PINn_CHANNEL() macros.

Regarding the changes to the example, my goal was to make a simplified example that would provide the least opportunities to confuse a beginner, the softpwm version of the Blink sketch. I do think it would be a good idea to also add a non-blocking example sketch. I have added this to my to-do list: #4.

@Palatis
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I don't really want to merge those SOFTPWM_DEFINE_PINn_CHANNEL() macros, because there are just too many of them...
I mean, see, there're a dozen AVR variants out there... we would make the macro list long like hell if we're going to support, say, 5~10 of them.

however I do get inspired by some of your codes, and may apply some of them to my own codebase if you don't mind.
but since I'm busy on some other things that may take some time to happen.

@per1234
Copy link
Owner Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I don't really want to merge those SOFTPWM_DEFINE_PINn_CHANNEL() macros, because there are just too many of them...

I understand. My goal was to make it easy for the average Arduino user to use your library without having to look at a datasheet. For that purpose I think only ATmega328P, ATmega32U4, and ATmega2560 are needed. Anyone using a different AVR will be knowledgeable enough to use SOFTPWM_DEFINE_CHANNEL(). I ended up going overboard by adding support for all the ATmega1284P pinouts. I hadn't realized there were so many before I started. It's not a very good system but I haven't been able to come up with anything better for defining the channels using Arduino pin numbers.

however I do get inspired by some of your codes, and may apply some of them to my own codebase if you don't mind.
but since I'm busy on some other things that may take some time to happen.

I'm very happy to hear that! As I said, if you want me to submit a pull request for any feature just let me know, I'd be happy to do so. Thanks so much for writing this excellent library. I've tried all the soft PWM code I could find and yours is best by far. I was just starting with Arduino when I first using the library so I wanted to use that perspective to attempt to make it more accessible to beginners.

@Palatis
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

yeah I tried every SoftPWM libraries before I started this one.
all of them use some kind of loop to iterate through PWM channels, and rely on the port_to_output_PGM, port_to_mode_PGM, digital_pin_to_bit_mask_PGM PROGMEM arrays, and doesn't generate "good enough asm" (compared to my hand-cranked ones).

the problem with those *_PGM array is that the compiler tends to deference them at run time (instead of compile time), thus introduce lots of overheads (~250% compared to mine).

I actually did a gcc -E to see if they actually output the asm I wanted, and my library generates 4 asm instructions per channel (5 if the shift-by-one is used)...

Please sign in to comment.