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if() else if() VS if() else if() in PWM control
The Next CEO of Stack OverflowPWM Motor Speed ControlPIC32 PWM minimal examplePWM Control with MOSFET switchMotor control using PWMPWM 1HZ PIC18F14K50PWM Control vs Variable Voltage Control - Calculating Duty CycleSolenoid control over PWMDimming multiple LED panels without PWM to LEDs; modified DMX control or something else?PWM voltage control that can handle 20APWM Power Control
$begingroup$
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)= (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 yesterday
TammerTheHammerTammerTheHammer
729
$endgroup$
|
show 1 more comment
$begingroup$
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)= (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 yesterday
TammerTheHammerTammerTheHammer
729
$endgroup$
1
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
1
$begingroup$
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
yesterday
4
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
|
show 1 more comment
$begingroup$
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)= (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 yesterday
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)= (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 yesterday
TammerTheHammerTammerTheHammer
729
asked yesterday
TammerTheHammerTammerTheHammer
729
edited yesterday
TammerTheHammer
asked yesterday
TammerTheHammerTammerTheHammer
729
asked yesterday
TammerTheHammerTammerTheHammer
729
asked yesterday
TammerTheHammerTammerTheHammer
729
729
1
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
1
$begingroup$
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
yesterday
4
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
|
show 1 more comment
1
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
1
$begingroup$
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
yesterday
4
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
1
1
$begingroup$
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
yesterday
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
$begingroup$
@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
yesterday
1
1
$begingroup$
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
yesterday
$begingroup$
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
yesterday
4
4
$begingroup$
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
yesterday
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
$begingroup$
@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
yesterday
|
show 1 more comment
2 Answers
2
active
oldest
votes
$begingroup$
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 yesterday
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
yesterday
7
$begingroup$
@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
yesterday
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
yesterday
2
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
yesterday
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
yesterday
|
show 1 more comment
$begingroup$
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 yesterday
TammerTheHammerTammerTheHammer
729
$endgroup$
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
yesterday
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
2
$begingroup$
Sidenote: To my understanding misra requireselseonly at the end ofif ... else ifconstructs, and not on plain if statements.
$endgroup$
– user694733
yesterday
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
yesterday
|
show 2 more comments
Your Answer
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
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 yesterday
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
yesterday
7
$begingroup$
@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
yesterday
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
yesterday
2
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
yesterday
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
yesterday
|
show 1 more comment
$begingroup$
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 yesterday
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
yesterday
7
$begingroup$
@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
yesterday
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
yesterday
2
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
yesterday
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
yesterday
|
show 1 more comment
$begingroup$
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 yesterday
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 yesterday
Jeroen3Jeroen3
11.6k1748
answered yesterday
Jeroen3Jeroen3
11.6k1748
answered yesterday
Jeroen3Jeroen3
11.6k1748
answered yesterday
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
yesterday
7
$begingroup$
@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
yesterday
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
yesterday
2
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
yesterday
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
yesterday
|
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
yesterday
7
$begingroup$
@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
yesterday
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
yesterday
2
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
yesterday
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
yesterday
$begingroup$
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
yesterday
$begingroup$
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
yesterday
7
7
$begingroup$
@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
yesterday
$begingroup$
@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
yesterday
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
yesterday
$begingroup$
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
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– Hasan alattar
yesterday
2
2
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
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– Marko Buršič
yesterday
$begingroup$
@TammerTheHammer Well, looking at the question tittle, people would think you are asking how to use if then statements.
$endgroup$
– Marko Buršič
yesterday
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
yesterday
$begingroup$
@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
yesterday
|
show 1 more comment
$begingroup$
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 yesterday
TammerTheHammerTammerTheHammer
729
$endgroup$
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
yesterday
$begingroup$
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
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– Hasan alattar
yesterday
$begingroup$
@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
yesterday
2
$begingroup$
Sidenote: To my understanding misra requireselseonly at the end ofif ... else ifconstructs, and not on plain if statements.
$endgroup$
– user694733
yesterday
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
yesterday
|
show 2 more comments
$begingroup$
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 yesterday
TammerTheHammerTammerTheHammer
729
$endgroup$
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
yesterday
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
2
$begingroup$
Sidenote: To my understanding misra requireselseonly at the end ofif ... else ifconstructs, and not on plain if statements.
$endgroup$
– user694733
yesterday
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
yesterday
|
show 2 more comments
$begingroup$
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 yesterday
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 yesterday
TammerTheHammerTammerTheHammer
729
edited yesterday
answered yesterday
TammerTheHammerTammerTheHammer
729
answered yesterday
TammerTheHammerTammerTheHammer
729
answered yesterday
TammerTheHammerTammerTheHammer
729
729
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
yesterday
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
2
$begingroup$
Sidenote: To my understanding misra requireselseonly at the end ofif ... else ifconstructs, and not on plain if statements.
$endgroup$
– user694733
yesterday
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
yesterday
|
show 2 more comments
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
yesterday
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
2
$begingroup$
Sidenote: To my understanding misra requireselseonly at the end ofif ... else ifconstructs, and not on plain if statements.
$endgroup$
– user694733
yesterday
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
yesterday
4
4
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
yesterday
$begingroup$
Posting of your own solution to a problem is encouraged.
$endgroup$
– AndrejaKo
yesterday
$begingroup$
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
yesterday
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
$begingroup$
@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
yesterday
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
yesterday
$begingroup$
Sidenote: To my understanding misra requires
else only at the end of if ... else if constructs, and not on plain if statements.$endgroup$
– user694733
yesterday
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
yesterday
$begingroup$
@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
yesterday
|
show 2 more comments
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1
$begingroup$
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
yesterday
$begingroup$
@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
yesterday
1
$begingroup$
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
yesterday
4
$begingroup$
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
yesterday
$begingroup$
@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
yesterday