When I run this code

Projects Programming
1

When I run this code

unsigned long currentMicros();
unsigned long previousMicros();
unsigned long halfPeriod = 8336UL; // 1/60/2 = 8.333uS
void setup() {
  pinMode (2, OUTPUT);
}
void loop() {
  while (1) {
    currentMicros = micros();
    if ((currentMicros - previousMicros) >= halfPeriod) {
      PIND = PIND | 0b00000100; // toggle D2 by writing to input register
    }
  }
}

I get this error

Arduino: 1.6.8 (Windows XP), Board: "Arduino/Genuino Uno"

C:\Program Files\Arduino\arduino-builder -dump-prefs -logger=machine -hardware "C:\Program Files\Arduino\hardware" -tools "C:\Program Files\Arduino\tools-builder" -tools "C:\Program Files\Arduino\hardware\tools\avr" -built-in-libraries "C:\Program Files\Arduino\libraries" -libraries "C:\Documents and Settings\bubba\My Documents\Arduino\libraries" -fqbn=arduino:avr:uno -vid-pid=0X2341_0X0043 -ide-version=10608 -build-path "C:\DOCUME~1\bubba\LOCALS~1\Temp\builde26afc21b16c627a750719d4db91a20c.tmp" -warnings=default -prefs=build.warn_data_percentage=75 -verbose "C:\Documents and Settings\bubba\My Documents\Arduino\sketch_may05b\sketch_may05b.ino"
C:\Program Files\Arduino\arduino-builder -compile -logger=machine -hardware "C:\Program Files\Arduino\hardware" -tools "C:\Program Files\Arduino\tools-builder" -tools "C:\Program Files\Arduino\hardware\tools\avr" -built-in-libraries "C:\Program Files\Arduino\libraries" -libraries "C:\Documents and Settings\bubba\My Documents\Arduino\libraries" -fqbn=arduino:avr:uno -vid-pid=0X2341_0X0043 -ide-version=10608 -build-path "C:\DOCUME~1\bubba\LOCALS~1\Temp\builde26afc21b16c627a750719d4db91a20c.tmp" -warnings=default -prefs=build.warn_data_percentage=75 -verbose "C:\Documents and Settings\bubba\My Documents\Arduino\sketch_may05b\sketch_may05b.ino"
"C:\Program Files\Arduino\hardware\tools\avr/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -w -x c++ -E -CC -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10608 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR "-IC:\Program Files\Arduino\hardware\arduino\avr\cores\arduino" "-IC:\Program Files\Arduino\hardware\arduino\avr\variants\standard" "C:\DOCUME~1\bubba\LOCALS~1\Temp\builde26afc21b16c627a750719d4db91a20c.tmp\sketch\sketch_may05b.ino.cpp" -o "nul"
"C:\Program Files\Arduino\hardware\tools\avr/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -w -x c++ -E -CC -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10608 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR "-IC:\Program Files\Arduino\hardware\arduino\avr\cores\arduino" "-IC:\Program Files\Arduino\hardware\arduino\avr\variants\standard" "C:\DOCUME~1\bubba\LOCALS~1\Temp\builde26afc21b16c627a750719d4db91a20c.tmp\sketch\sketch_may05b.ino.cpp" -o "nul"
"C:\Program Files\Arduino\hardware\tools\avr/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -w -x c++ -E -CC -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10608 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR "-IC:\Program Files\Arduino\hardware\arduino\avr\cores\arduino" "-IC:\Program Files\Arduino\hardware\arduino\avr\variants\standard" "C:\DOCUME~1\bubba\LOCALS~1\Temp\builde26afc21b16c627a750719d4db91a20c.tmp\sketch\sketch_may05b.ino.cpp" -o "C:\DOCUME~1\bubba\LOCALS~1\Temp\builde26afc21b16c627a750719d4db91a20c.tmp\preproc\ctags_target_for_gcc_minus_e.cpp"
"C:\Program Files\Arduino\tools-builder\ctags\5.8-arduino10/ctags" -u --language-force=c++ -f - --c++-kinds=svpf --fields=KSTtzns --line-directives "C:\DOCUME~1\bubba\LOCALS~1\Temp\builde26afc21b16c627a750719d4db91a20c.tmp\preproc\ctags_target_for_gcc_minus_e.cpp"
"C:\Program Files\Arduino\hardware\tools\avr/bin/avr-g++" -c -g -Os -std=gnu++11 -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -MMD -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10608 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR "-IC:\Program Files\Arduino\hardware\arduino\avr\cores\arduino" "-IC:\Program Files\Arduino\hardware\arduino\avr\variants\standard" "C:\DOCUME~1\bubba\LOCALS~1\Temp\builde26afc21b16c627a750719d4db91a20c.tmp\sketch\sketch_may05b.ino.cpp" -o "C:\DOCUME~1\bubba\LOCALS~1\Temp\builde26afc21b16c627a750719d4db91a20c.tmp\sketch\sketch_may05b.ino.cpp.o"
C:\Documents and Settings\bubba\My Documents\Arduino\sketch_may05b\sketch_may05b.ino: In function 'void loop()':

sketch_may05b:9: error: assignment of function 'long unsigned int currentMicros()'

currentMicros = micros();

^

sketch_may05b:9: error: cannot convert 'long unsigned int' to 'long unsigned int()' in assignment

sketch_may05b:10: error: ISO C++ forbids using pointer to a function in subtraction [-fpermissive]

if ((currentMicros - previousMicros) >= halfPeriod) {

^

exit status 1
assignment of function 'long unsigned int currentMicros()'

Any help on how to google these errors so I can fix them would be appreciated

2

I didn't try it, but you should remove the parentheses from your variables. Your sketch thinks those are functions.

// change these
unsigned long currentMicros();
unsigned long previousMicros();
// to these
unsigned long currentMicros;
unsigned long previousMicros;
3

That did the trick! There is just no substitute for real knowledge. Thank you.

4

Just the difference:

Your version declared a function prototype. SurferTim's version declared a variable.

5

Bubba001:
That did the trick! There is just no substitute for real knowledge. Thank you.

Sometimes documentation attempts to fill that gap.