![]() Although I do have C experience, I've never programmed with it on microcontrollers. My experience is mostly with Assembly and Basic. It sounds like I might have a problem with timer0, right? I don't know what to do about that. I also tried the LCD hello world example that prints the number of running seconds using the millis() and the number just stays at zero. Certain things do go on while the delay () function is controlling the Atmega chip, however, because the delay function does not disable interrupts. I tried some of the example codes to see if they worked and every one that contains a delay(#) stops working right at the delay line. More knowledgeable programmers usually avoid the use of delay () for timing of events longer than 10’s of milliseconds unless the Arduino sketch is very simple. After removing all my delays, everything worked again. When I plugged it in today to begin programming some more, after trying the program that worked yesterday, it didn't work anymore today. For some reason all my delays in my code stopped working today. You can of course stop interrupts before calling delayMicroseconds() and enable them afterwards, but that again does impact timing accuracy by the duration of compiled code for enabling/disabling.I just finished wiring a bunch of LCD displays that I was about to interface with my Mega today. When an interrupt is received during the execution of the delayMicroseconds(), the timing of delayMicroseconds() will be wrong. "brne 1b" : "=w" (us) : "0" (us) // 2 cyclesīTW: The compiled code is pretty accurate, but be aware of the following: On Arduino there are timed interrupts configured that most are unaware of. account for the time taken in the preceeding commands. ![]() per iteration, so execute it four times for each microsecond of the following loop takes a quarter of a microsecond (4 cycles) of the function call yields a delay of approximately 1 1/8 us. ![]() for a one-microsecond delay, simply return. (Hint: rename the class to microDelay and replace occurrences of millis() with micros() ) Freezing/Pausing. It is left as an exercise to the reader to write that class. millisDelay counts the delay in milliseconds. for the 16 MHz clock on most Arduino boards delay() to return the delay value that was passed to start() Microsecond version of the library. 2 microseconds) gives delays longer than desired. calling avrlib's delay_us() function with low values (e.g. Calling _asm_-code from C requires some extra instructions to save CPU registers.įor a normal Arduino only the following code will be compiled: /* Delay for the given number of microseconds. The last -2 microseconds (before the loop is kicked off) is again a correction on compiler introduced overhead. 16MHz/(4×4) = 1MHz, which takes 1 us cycle time, the resolution that we are after. The _asm_-loop compiles into a 4 CPU cycle loop. Then the delay value is multiplied by four ( <<=2). That an assumption of the author! The number of CPU cycles 'burnt' by each instruction is well documented in the Atmel AVR instruction set document.įirst the delay value is checked for being equal to 1, in that case just returning from the routine already spent over a microsecond of CPU time. The code heavily relies on compiler optimization being exactly the same for you as for the developer of the library. ![]() For now just focus on this single function, it doesn't rely on any other fucntions.īy inspecting the code you'll notice that it is not about timers, it is all about instruction cycles. Take the effort of finding the file and browsing through it. ![]() Windows systems will have a similar path to the wiring.c file. The source code for this function is fairly well documented and can be found in /usr/share/arduino/hardware/arduino/cores/arduino/wiring.c on Linux systems. ![]()
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