if(){} else{} if(){} VS if(){} else if(){} in PWM control
0
$begingroup$
I'm using timer0 and a gpio pin to generate a 300Hz PWM signal on an ATmega2560.
The details if you care: F_CPU=16M, timer clock prescaler /256, count_max=208
The frequency changes depending on if I use an "if(){} else{} if(){}" or an "if(){} else if(){}".
The first generates 300Hz and the second generates 244Hz. Below is the code that generates the correct frequency. If I delete the curly brackets after the first two else's, I get 244Hz.
void pwm_on(uint8_t duty){
if(TCNT0 <= duty){ //portion of counter active
PORTB |= (1<<7); //turn on PB7
} else {}
if(TCNT0 >= duty){ //portion of counter inactive
PORTB &= ~(1<<7);//turn off PB7
} else {}
if(TCNT0 >= COUNT_MAX){ //if counter full
TCNT0=0;//reset counter
} else {}
}//pwm_on
Why am I getting such a significant frequency change with code that doesn't change the functionality?
Also calling this function is the only thing I do in Main after initializing.
pwm timer firmware
asked 6 hours ago
TammerTheHammerTammerTheHammer
729
$endgroup$
|
show 1 more comment
0
$begingroup$
I'm using timer0 and a gpio pin to generate a 300Hz PWM signal on an ATmega2560.
The details if you care: F_CPU=16M, timer clock prescaler /256, count_max=208
The frequency changes depending on if I use an "if(){} else{} if(){}" or an "if(){} else if(){}".
The first generates 300Hz and the second generates 244Hz. Below is the code that generates the correct frequency. If I delete the curly brackets after the first two else's, I get 244Hz.
void pwm_on(uint8_t duty){
if(TCNT0 <= duty){ //portion of counter active
PORTB |= (1<<7); //turn on PB7
} else {}
if(TCNT0 >= duty){ //portion of counter inactive
PORTB &= ~(1<<7);//turn off PB7
} else {}
if(TCNT0 >= COUNT_MAX){ //if counter full
TCNT0=0;//reset counter
} else {}
}//pwm_on
Why am I getting such a significant frequency change with code that doesn't change the functionality?
Also calling this function is the only thing I do in Main after initializing.
pwm timer firmware
asked 6 hours ago
TammerTheHammerTammerTheHammer
729
$endgroup$
$begingroup$
I'm voting to close this question as off-topic because it's a C syntax understanding problem and has nothing specifically to do with the hardware the code is running on.
$endgroup$
– brhans
2 hours ago
$begingroup$
@brhans I edited the title of the question to specify it is for PWM control since that seems to be the largest point of contention for moving this question to stackoverflow. I am not a computer programmer and this is not a computer programming question. It is about how the syntax is affecting register level hardware timer0, NOT why doesn't this syntax work.
$endgroup$
– TammerTheHammer
2 hours ago
$begingroup$
It doesn't really matter what the end application is - your problem is that you're not understanding standard C syntax. You would have this same problem if you were writing similarly structured code to run on a PC. The fact that you're writing firmware for a micro is only relevant in how this problem is presenting itself - it's just the symptom.
$endgroup$
– brhans
1 hour ago
2
$begingroup$
Why aren't you using the perhipheral to generate the PWM for you? Which would allow you to dedicate zero CPU time to this task.
$endgroup$
– Attie
57 mins ago
$begingroup$
@brhans I have only been asking about the symptom, that being the change in frequency. My understanding shouldn't matter since the question has always been about the symptom.
$endgroup$
– TammerTheHammer
28 mins ago
|
show 1 more comment
0
0
0
$begingroup$
I'm using timer0 and a gpio pin to generate a 300Hz PWM signal on an ATmega2560.
The details if you care: F_CPU=16M, timer clock prescaler /256, count_max=208
The frequency changes depending on if I use an "if(){} else{} if(){}" or an "if(){} else if(){}".
The first generates 300Hz and the second generates 244Hz. Below is the code that generates the correct frequency. If I delete the curly brackets after the first two else's, I get 244Hz.
void pwm_on(uint8_t duty){
if(TCNT0 <= duty){ //portion of counter active
PORTB |= (1<<7); //turn on PB7
} else {}
if(TCNT0 >= duty){ //portion of counter inactive
PORTB &= ~(1<<7);//turn off PB7
} else {}
if(TCNT0 >= COUNT_MAX){ //if counter full
TCNT0=0;//reset counter
} else {}
}//pwm_on
Why am I getting such a significant frequency change with code that doesn't change the functionality?
Also calling this function is the only thing I do in Main after initializing.
pwm timer firmware
asked 6 hours ago
TammerTheHammerTammerTheHammer
729
$endgroup$
I'm using timer0 and a gpio pin to generate a 300Hz PWM signal on an ATmega2560.
The details if you care: F_CPU=16M, timer clock prescaler /256, count_max=208
The frequency changes depending on if I use an "if(){} else{} if(){}" or an "if(){} else if(){}".
The first generates 300Hz and the second generates 244Hz. Below is the code that generates the correct frequency. If I delete the curly brackets after the first two else's, I get 244Hz.
void pwm_on(uint8_t duty){
if(TCNT0 <= duty){ //portion of counter active
PORTB |= (1<<7); //turn on PB7
} else {}
if(TCNT0 >= duty){ //portion of counter inactive
PORTB &= ~(1<<7);//turn off PB7
} else {}
if(TCNT0 >= COUNT_MAX){ //if counter full
TCNT0=0;//reset counter
} else {}
}//pwm_on
Why am I getting such a significant frequency change with code that doesn't change the functionality?
Also calling this function is the only thing I do in Main after initializing.
pwm timer firmware
pwm timer firmware
asked 6 hours ago
TammerTheHammerTammerTheHammer
729
asked 6 hours ago
TammerTheHammerTammerTheHammer
729
edited 2 hours ago
TammerTheHammer
asked 6 hours ago
TammerTheHammerTammerTheHammer
729
asked 6 hours ago
TammerTheHammerTammerTheHammer
729
asked 6 hours ago
TammerTheHammerTammerTheHammer
729
729
$begingroup$
I'm voting to close this question as off-topic because it's a C syntax understanding problem and has nothing specifically to do with the hardware the code is running on.
$endgroup$
– brhans
2 hours ago
$begingroup$
@brhans I edited the title of the question to specify it is for PWM control since that seems to be the largest point of contention for moving this question to stackoverflow. I am not a computer programmer and this is not a computer programming question. It is about how the syntax is affecting register level hardware timer0, NOT why doesn't this syntax work.
$endgroup$
– TammerTheHammer
2 hours ago
$begingroup$
It doesn't really matter what the end application is - your problem is that you're not understanding standard C syntax. You would have this same problem if you were writing similarly structured code to run on a PC. The fact that you're writing firmware for a micro is only relevant in how this problem is presenting itself - it's just the symptom.
$endgroup$
– brhans
1 hour ago
2
$begingroup$
Why aren't you using the perhipheral to generate the PWM for you? Which would allow you to dedicate zero CPU time to this task.
$endgroup$
– Attie
57 mins ago
$begingroup$
@brhans I have only been asking about the symptom, that being the change in frequency. My understanding shouldn't matter since the question has always been about the symptom.
$endgroup$
– TammerTheHammer
28 mins ago
|
show 1 more comment
$begingroup$
I'm voting to close this question as off-topic because it's a C syntax understanding problem and has nothing specifically to do with the hardware the code is running on.
$endgroup$
– brhans
2 hours ago
$begingroup$
@brhans I edited the title of the question to specify it is for PWM control since that seems to be the largest point of contention for moving this question to stackoverflow. I am not a computer programmer and this is not a computer programming question. It is about how the syntax is affecting register level hardware timer0, NOT why doesn't this syntax work.
$endgroup$
– TammerTheHammer
2 hours ago
$begingroup$
It doesn't really matter what the end application is - your problem is that you're not understanding standard C syntax. You would have this same problem if you were writing similarly structured code to run on a PC. The fact that you're writing firmware for a micro is only relevant in how this problem is presenting itself - it's just the symptom.
$endgroup$
– brhans
1 hour ago
2
$begingroup$
Why aren't you using the perhipheral to generate the PWM for you? Which would allow you to dedicate zero CPU time to this task.
$endgroup$
– Attie
57 mins ago
$begingroup$
@brhans I have only been asking about the symptom, that being the change in frequency. My understanding shouldn't matter since the question has always been about the symptom.
$endgroup$
– TammerTheHammer
28 mins ago
$begingroup$
I'm voting to close this question as off-topic because it's a C syntax understanding problem and has nothing specifically to do with the hardware the code is running on.
$endgroup$
– brhans
2 hours ago
$begingroup$
I'm voting to close this question as off-topic because it's a C syntax understanding problem and has nothing specifically to do with the hardware the code is running on.
$endgroup$
– brhans
2 hours ago
$begingroup$
@brhans I edited the title of the question to specify it is for PWM control since that seems to be the largest point of contention for moving this question to stackoverflow. I am not a computer programmer and this is not a computer programming question. It is about how the syntax is affecting register level hardware timer0, NOT why doesn't this syntax work.
$endgroup$
– TammerTheHammer
2 hours ago
$begingroup$
@brhans I edited the title of the question to specify it is for PWM control since that seems to be the largest point of contention for moving this question to stackoverflow. I am not a computer programmer and this is not a computer programming question. It is about how the syntax is affecting register level hardware timer0, NOT why doesn't this syntax work.
$endgroup$
– TammerTheHammer
2 hours ago
$begingroup$
It doesn't really matter what the end application is - your problem is that you're not understanding standard C syntax. You would have this same problem if you were writing similarly structured code to run on a PC. The fact that you're writing firmware for a micro is only relevant in how this problem is presenting itself - it's just the symptom.
$endgroup$
– brhans
1 hour ago
$begingroup$
It doesn't really matter what the end application is - your problem is that you're not understanding standard C syntax. You would have this same problem if you were writing similarly structured code to run on a PC. The fact that you're writing firmware for a micro is only relevant in how this problem is presenting itself - it's just the symptom.
$endgroup$
– brhans
1 hour ago
2
2
$begingroup$
Why aren't you using the perhipheral to generate the PWM for you? Which would allow you to dedicate zero CPU time to this task.
$endgroup$
– Attie
57 mins ago
$begingroup$
Why aren't you using the perhipheral to generate the PWM for you? Which would allow you to dedicate zero CPU time to this task.
$endgroup$
– Attie
57 mins ago
$begingroup$
@brhans I have only been asking about the symptom, that being the change in frequency. My understanding shouldn't matter since the question has always been about the symptom.
$endgroup$
– TammerTheHammer
28 mins ago
$begingroup$
@brhans I have only been asking about the symptom, that being the change in frequency. My understanding shouldn't matter since the question has always been about the symptom.
$endgroup$
– TammerTheHammer
28 mins ago
|
show 1 more comment
2 Answers
2
active
oldest
votes
4
$begingroup$
This is more a code syntax question. Could be offtopic, might be moved to stackoverflow.
if(){} else{} if(){} and if(){} else if(){} are different.
With correct indentation and brackets the issue is immediately visible:
if(){} else{} if(){}
if(condition){
statement
}else{
statement
}
if(condition){
statement
}
And
if(){} else if(){}
if(condition){
statement
}else{
if(condition){
statement
}
}
answered 5 hours ago
Jeroen3Jeroen3
11.6k1748
$endgroup$
$begingroup$
i'm asking about the change in frequency (hardware) caused by the change in syntax (code) which is why I asked it here.
$endgroup$
– TammerTheHammer
5 hours ago
6
$begingroup$
@TammerTheHammer Of course, but you should learn to use if-else-elseif statements to solve the puzzle. It's not the hardware, but your code.
$endgroup$
– Marko Buršič
5 hours ago
1
$begingroup$
electronics.stackexchange.com/help/on-topic / @TammerTheHammer you asked in the right stack. this has been discussed many times before and some people try to redirect others to stackOverflow while actually you should ask here for softwares related to programming microcontrollers
$endgroup$
– Hasan alattar
5 hours ago
1
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
4 hours ago
1
$begingroup$
@TammerTheHammer You haven't asked how to use if-else, but that's only because you don't realize it's the root of your problem.code that doesn't change the functionality- here it is.
$endgroup$
– Agent_L
3 hours ago
|
show 1 more comment
2
$begingroup$
The reason why my frequency goes down and the period goes up with the "if(){} else if(){}" is because TCNT0 >= duty is always true when TCNT0 >= COUNT_MAX so the last statement that resets the counter at COUNT_MAX never runs so my counter overflows instead of resetting at a count that gets me a frequency of 300Hz.
I figured it out pretty quickly after posting, sorry if I am misusing this site, I'm posting a question on meta to see what the collective thinks so I can learn and use this resource as best as possible.
answered 5 hours ago
TammerTheHammerTammerTheHammer
729
$endgroup$
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
5 hours ago
$begingroup$
if you compile without optimaziation i think you will get same frequency but much lower than 244Hz anyway. i find it wierd that you right else {}. check this out : cpp.sh/3rcrt
$endgroup$
– Hasan alattar
4 hours ago
$begingroup$
@Hasanalattar I'll need to research more on compiling before I'll understand this, but why I use else{} is because i learned misra-c standard in school and it was drilled into my brain that all if(){} statements must have its accompanying else{}.
$endgroup$
– TammerTheHammer
4 hours ago
2
$begingroup$
Sidenote: To my understanding misra requireselse{}only at the end ofif ... else ifconstructs, and not on plain if statements.
$endgroup$
– user694733
3 hours ago
1
$begingroup$
@TammerTheHammer I tried looking for that MISRA rule, and as far as I can tell there is no such rule. There is one for chained if .. else if ... else if ... which sort of make sense but for a simpleifthere is no need for an emptyelse
$endgroup$
– r_ahlskog
3 hours ago
|
show 1 more comment
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
4
$begingroup$
This is more a code syntax question. Could be offtopic, might be moved to stackoverflow.
if(){} else{} if(){} and if(){} else if(){} are different.
With correct indentation and brackets the issue is immediately visible:
if(){} else{} if(){}
if(condition){
statement
}else{
statement
}
if(condition){
statement
}
And
if(){} else if(){}
if(condition){
statement
}else{
if(condition){
statement
}
}
answered 5 hours ago
Jeroen3Jeroen3
11.6k1748
$endgroup$
$begingroup$
i'm asking about the change in frequency (hardware) caused by the change in syntax (code) which is why I asked it here.
$endgroup$
– TammerTheHammer
5 hours ago
6
$begingroup$
@TammerTheHammer Of course, but you should learn to use if-else-elseif statements to solve the puzzle. It's not the hardware, but your code.
$endgroup$
– Marko Buršič
5 hours ago
1
$begingroup$
electronics.stackexchange.com/help/on-topic / @TammerTheHammer you asked in the right stack. this has been discussed many times before and some people try to redirect others to stackOverflow while actually you should ask here for softwares related to programming microcontrollers
$endgroup$
– Hasan alattar
5 hours ago
1
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
4 hours ago
1
$begingroup$
@TammerTheHammer You haven't asked how to use if-else, but that's only because you don't realize it's the root of your problem.code that doesn't change the functionality- here it is.
$endgroup$
– Agent_L
3 hours ago
|
show 1 more comment
4
$begingroup$
This is more a code syntax question. Could be offtopic, might be moved to stackoverflow.
if(){} else{} if(){} and if(){} else if(){} are different.
With correct indentation and brackets the issue is immediately visible:
if(){} else{} if(){}
if(condition){
statement
}else{
statement
}
if(condition){
statement
}
And
if(){} else if(){}
if(condition){
statement
}else{
if(condition){
statement
}
}
answered 5 hours ago
Jeroen3Jeroen3
11.6k1748
$endgroup$
$begingroup$
i'm asking about the change in frequency (hardware) caused by the change in syntax (code) which is why I asked it here.
$endgroup$
– TammerTheHammer
5 hours ago
6
$begingroup$
@TammerTheHammer Of course, but you should learn to use if-else-elseif statements to solve the puzzle. It's not the hardware, but your code.
$endgroup$
– Marko Buršič
5 hours ago
1
$begingroup$
electronics.stackexchange.com/help/on-topic / @TammerTheHammer you asked in the right stack. this has been discussed many times before and some people try to redirect others to stackOverflow while actually you should ask here for softwares related to programming microcontrollers
$endgroup$
– Hasan alattar
5 hours ago
1
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
4 hours ago
1
$begingroup$
@TammerTheHammer You haven't asked how to use if-else, but that's only because you don't realize it's the root of your problem.code that doesn't change the functionality- here it is.
$endgroup$
– Agent_L
3 hours ago
|
show 1 more comment
4
4
4
$begingroup$
This is more a code syntax question. Could be offtopic, might be moved to stackoverflow.
if(){} else{} if(){} and if(){} else if(){} are different.
With correct indentation and brackets the issue is immediately visible:
if(){} else{} if(){}
if(condition){
statement
}else{
statement
}
if(condition){
statement
}
And
if(){} else if(){}
if(condition){
statement
}else{
if(condition){
statement
}
}
answered 5 hours ago
Jeroen3Jeroen3
11.6k1748
$endgroup$
This is more a code syntax question. Could be offtopic, might be moved to stackoverflow.
if(){} else{} if(){} and if(){} else if(){} are different.
With correct indentation and brackets the issue is immediately visible:
if(){} else{} if(){}
if(condition){
statement
}else{
statement
}
if(condition){
statement
}
And
if(){} else if(){}
if(condition){
statement
}else{
if(condition){
statement
}
}
answered 5 hours ago
Jeroen3Jeroen3
11.6k1748
answered 5 hours ago
Jeroen3Jeroen3
11.6k1748
answered 5 hours ago
Jeroen3Jeroen3
11.6k1748
answered 5 hours ago
Jeroen3Jeroen3
11.6k1748
11.6k1748
$begingroup$
i'm asking about the change in frequency (hardware) caused by the change in syntax (code) which is why I asked it here.
$endgroup$
– TammerTheHammer
5 hours ago
6
$begingroup$
@TammerTheHammer Of course, but you should learn to use if-else-elseif statements to solve the puzzle. It's not the hardware, but your code.
$endgroup$
– Marko Buršič
5 hours ago
1
$begingroup$
electronics.stackexchange.com/help/on-topic / @TammerTheHammer you asked in the right stack. this has been discussed many times before and some people try to redirect others to stackOverflow while actually you should ask here for softwares related to programming microcontrollers
$endgroup$
– Hasan alattar
5 hours ago
1
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
4 hours ago
1
$begingroup$
@TammerTheHammer You haven't asked how to use if-else, but that's only because you don't realize it's the root of your problem.code that doesn't change the functionality- here it is.
$endgroup$
– Agent_L
3 hours ago
|
show 1 more comment
$begingroup$
i'm asking about the change in frequency (hardware) caused by the change in syntax (code) which is why I asked it here.
$endgroup$
– TammerTheHammer
5 hours ago
6
$begingroup$
@TammerTheHammer Of course, but you should learn to use if-else-elseif statements to solve the puzzle. It's not the hardware, but your code.
$endgroup$
– Marko Buršič
5 hours ago
1
$begingroup$
electronics.stackexchange.com/help/on-topic / @TammerTheHammer you asked in the right stack. this has been discussed many times before and some people try to redirect others to stackOverflow while actually you should ask here for softwares related to programming microcontrollers
$endgroup$
– Hasan alattar
5 hours ago
1
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
4 hours ago
1
$begingroup$
@TammerTheHammer You haven't asked how to use if-else, but that's only because you don't realize it's the root of your problem.code that doesn't change the functionality- here it is.
$endgroup$
– Agent_L
3 hours ago
$begingroup$
i'm asking about the change in frequency (hardware) caused by the change in syntax (code) which is why I asked it here.
$endgroup$
– TammerTheHammer
5 hours ago
$begingroup$
i'm asking about the change in frequency (hardware) caused by the change in syntax (code) which is why I asked it here.
$endgroup$
– TammerTheHammer
5 hours ago
6
6
$begingroup$
@TammerTheHammer Of course, but you should learn to use if-else-elseif statements to solve the puzzle. It's not the hardware, but your code.
$endgroup$
– Marko Buršič
5 hours ago
$begingroup$
@TammerTheHammer Of course, but you should learn to use if-else-elseif statements to solve the puzzle. It's not the hardware, but your code.
$endgroup$
– Marko Buršič
5 hours ago
1
1
$begingroup$
electronics.stackexchange.com/help/on-topic / @TammerTheHammer you asked in the right stack. this has been discussed many times before and some people try to redirect others to stackOverflow while actually you should ask here for softwares related to programming microcontrollers
$endgroup$
– Hasan alattar
5 hours ago
$begingroup$
electronics.stackexchange.com/help/on-topic / @TammerTheHammer you asked in the right stack. this has been discussed many times before and some people try to redirect others to stackOverflow while actually you should ask here for softwares related to programming microcontrollers
$endgroup$
– Hasan alattar
5 hours ago
1
1
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
4 hours ago
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
4 hours ago
1
1
$begingroup$
@TammerTheHammer You haven't asked how to use if-else, but that's only because you don't realize it's the root of your problem.
code that doesn't change the functionality - here it is.$endgroup$
– Agent_L
3 hours ago
$begingroup$
@TammerTheHammer You haven't asked how to use if-else, but that's only because you don't realize it's the root of your problem.
code that doesn't change the functionality - here it is.$endgroup$
– Agent_L
3 hours ago
|
show 1 more comment
2
$begingroup$
The reason why my frequency goes down and the period goes up with the "if(){} else if(){}" is because TCNT0 >= duty is always true when TCNT0 >= COUNT_MAX so the last statement that resets the counter at COUNT_MAX never runs so my counter overflows instead of resetting at a count that gets me a frequency of 300Hz.
I figured it out pretty quickly after posting, sorry if I am misusing this site, I'm posting a question on meta to see what the collective thinks so I can learn and use this resource as best as possible.
answered 5 hours ago
TammerTheHammerTammerTheHammer
729
$endgroup$
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
5 hours ago
$begingroup$
if you compile without optimaziation i think you will get same frequency but much lower than 244Hz anyway. i find it wierd that you right else {}. check this out : cpp.sh/3rcrt
$endgroup$
– Hasan alattar
4 hours ago
$begingroup$
@Hasanalattar I'll need to research more on compiling before I'll understand this, but why I use else{} is because i learned misra-c standard in school and it was drilled into my brain that all if(){} statements must have its accompanying else{}.
$endgroup$
– TammerTheHammer
4 hours ago
2
$begingroup$
Sidenote: To my understanding misra requireselse{}only at the end ofif ... else ifconstructs, and not on plain if statements.
$endgroup$
– user694733
3 hours ago
1
$begingroup$
@TammerTheHammer I tried looking for that MISRA rule, and as far as I can tell there is no such rule. There is one for chained if .. else if ... else if ... which sort of make sense but for a simpleifthere is no need for an emptyelse
$endgroup$
– r_ahlskog
3 hours ago
|
show 1 more comment
2
$begingroup$
The reason why my frequency goes down and the period goes up with the "if(){} else if(){}" is because TCNT0 >= duty is always true when TCNT0 >= COUNT_MAX so the last statement that resets the counter at COUNT_MAX never runs so my counter overflows instead of resetting at a count that gets me a frequency of 300Hz.
I figured it out pretty quickly after posting, sorry if I am misusing this site, I'm posting a question on meta to see what the collective thinks so I can learn and use this resource as best as possible.
answered 5 hours ago
TammerTheHammerTammerTheHammer
729
$endgroup$
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
5 hours ago
$begingroup$
if you compile without optimaziation i think you will get same frequency but much lower than 244Hz anyway. i find it wierd that you right else {}. check this out : cpp.sh/3rcrt
$endgroup$
– Hasan alattar
4 hours ago
$begingroup$
@Hasanalattar I'll need to research more on compiling before I'll understand this, but why I use else{} is because i learned misra-c standard in school and it was drilled into my brain that all if(){} statements must have its accompanying else{}.
$endgroup$
– TammerTheHammer
4 hours ago
2
$begingroup$
Sidenote: To my understanding misra requireselse{}only at the end ofif ... else ifconstructs, and not on plain if statements.
$endgroup$
– user694733
3 hours ago
1
$begingroup$
@TammerTheHammer I tried looking for that MISRA rule, and as far as I can tell there is no such rule. There is one for chained if .. else if ... else if ... which sort of make sense but for a simpleifthere is no need for an emptyelse
$endgroup$
– r_ahlskog
3 hours ago
|
show 1 more comment
2
2
2
$begingroup$
The reason why my frequency goes down and the period goes up with the "if(){} else if(){}" is because TCNT0 >= duty is always true when TCNT0 >= COUNT_MAX so the last statement that resets the counter at COUNT_MAX never runs so my counter overflows instead of resetting at a count that gets me a frequency of 300Hz.
I figured it out pretty quickly after posting, sorry if I am misusing this site, I'm posting a question on meta to see what the collective thinks so I can learn and use this resource as best as possible.
answered 5 hours ago
TammerTheHammerTammerTheHammer
729
$endgroup$
The reason why my frequency goes down and the period goes up with the "if(){} else if(){}" is because TCNT0 >= duty is always true when TCNT0 >= COUNT_MAX so the last statement that resets the counter at COUNT_MAX never runs so my counter overflows instead of resetting at a count that gets me a frequency of 300Hz.
I figured it out pretty quickly after posting, sorry if I am misusing this site, I'm posting a question on meta to see what the collective thinks so I can learn and use this resource as best as possible.
answered 5 hours ago
TammerTheHammerTammerTheHammer
729
edited 4 hours ago
answered 5 hours ago
TammerTheHammerTammerTheHammer
729
answered 5 hours ago
TammerTheHammerTammerTheHammer
729
answered 5 hours ago
TammerTheHammerTammerTheHammer
729
729
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
5 hours ago
$begingroup$
if you compile without optimaziation i think you will get same frequency but much lower than 244Hz anyway. i find it wierd that you right else {}. check this out : cpp.sh/3rcrt
$endgroup$
– Hasan alattar
4 hours ago
$begingroup$
@Hasanalattar I'll need to research more on compiling before I'll understand this, but why I use else{} is because i learned misra-c standard in school and it was drilled into my brain that all if(){} statements must have its accompanying else{}.
$endgroup$
– TammerTheHammer
4 hours ago
2
$begingroup$
Sidenote: To my understanding misra requireselse{}only at the end ofif ... else ifconstructs, and not on plain if statements.
$endgroup$
– user694733
3 hours ago
1
$begingroup$
@TammerTheHammer I tried looking for that MISRA rule, and as far as I can tell there is no such rule. There is one for chained if .. else if ... else if ... which sort of make sense but for a simpleifthere is no need for an emptyelse
$endgroup$
– r_ahlskog
3 hours ago
|
show 1 more comment
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
5 hours ago
$begingroup$
if you compile without optimaziation i think you will get same frequency but much lower than 244Hz anyway. i find it wierd that you right else {}. check this out : cpp.sh/3rcrt
$endgroup$
– Hasan alattar
4 hours ago
$begingroup$
@Hasanalattar I'll need to research more on compiling before I'll understand this, but why I use else{} is because i learned misra-c standard in school and it was drilled into my brain that all if(){} statements must have its accompanying else{}.
$endgroup$
– TammerTheHammer
4 hours ago
2
$begingroup$
Sidenote: To my understanding misra requireselse{}only at the end ofif ... else ifconstructs, and not on plain if statements.
$endgroup$
– user694733
3 hours ago
1
$begingroup$
@TammerTheHammer I tried looking for that MISRA rule, and as far as I can tell there is no such rule. There is one for chained if .. else if ... else if ... which sort of make sense but for a simpleifthere is no need for an emptyelse
$endgroup$
– r_ahlskog
3 hours ago
4
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
5 hours ago
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
5 hours ago
$begingroup$
if you compile without optimaziation i think you will get same frequency but much lower than 244Hz anyway. i find it wierd that you right else {}. check this out : cpp.sh/3rcrt
$endgroup$
– Hasan alattar
4 hours ago
$begingroup$
if you compile without optimaziation i think you will get same frequency but much lower than 244Hz anyway. i find it wierd that you right else {}. check this out : cpp.sh/3rcrt
$endgroup$
– Hasan alattar
4 hours ago
$begingroup$
@Hasanalattar I'll need to research more on compiling before I'll understand this, but why I use else{} is because i learned misra-c standard in school and it was drilled into my brain that all if(){} statements must have its accompanying else{}.
$endgroup$
– TammerTheHammer
4 hours ago
$begingroup$
@Hasanalattar I'll need to research more on compiling before I'll understand this, but why I use else{} is because i learned misra-c standard in school and it was drilled into my brain that all if(){} statements must have its accompanying else{}.
$endgroup$
– TammerTheHammer
4 hours ago
2
2
$begingroup$
Sidenote: To my understanding misra requires
else{} only at the end of if ... else if constructs, and not on plain if statements.$endgroup$
– user694733
3 hours ago
$begingroup$
Sidenote: To my understanding misra requires
else{} only at the end of if ... else if constructs, and not on plain if statements.$endgroup$
– user694733
3 hours ago
1
1
$begingroup$
@TammerTheHammer I tried looking for that MISRA rule, and as far as I can tell there is no such rule. There is one for chained if .. else if ... else if ... which sort of make sense but for a simple
if there is no need for an empty else$endgroup$
– r_ahlskog
3 hours ago
$begingroup$
@TammerTheHammer I tried looking for that MISRA rule, and as far as I can tell there is no such rule. There is one for chained if .. else if ... else if ... which sort of make sense but for a simple
if there is no need for an empty else$endgroup$
– r_ahlskog
3 hours ago
|
show 1 more comment
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$begingroup$
I'm voting to close this question as off-topic because it's a C syntax understanding problem and has nothing specifically to do with the hardware the code is running on.
$endgroup$
– brhans
2 hours ago
$begingroup$
@brhans I edited the title of the question to specify it is for PWM control since that seems to be the largest point of contention for moving this question to stackoverflow. I am not a computer programmer and this is not a computer programming question. It is about how the syntax is affecting register level hardware timer0, NOT why doesn't this syntax work.
$endgroup$
– TammerTheHammer
2 hours ago
$begingroup$
It doesn't really matter what the end application is - your problem is that you're not understanding standard C syntax. You would have this same problem if you were writing similarly structured code to run on a PC. The fact that you're writing firmware for a micro is only relevant in how this problem is presenting itself - it's just the symptom.
$endgroup$
– brhans
1 hour ago
2
$begingroup$
Why aren't you using the perhipheral to generate the PWM for you? Which would allow you to dedicate zero CPU time to this task.
$endgroup$
– Attie
57 mins ago
$begingroup$
@brhans I have only been asking about the symptom, that being the change in frequency. My understanding shouldn't matter since the question has always been about the symptom.
$endgroup$
– TammerTheHammer
28 mins ago