![]() Type is 16 bit and it is buggy (well, coded for speed) and doesn't work for large Is there any additional delay if I do that? Thanks.ĭelay is not accurate to 1ms, let alone us.ĭelayMicroseconds() cannot be called with very large arguments (because the I'm thinking to use delay() and delayMicroseconds() in sequence. In this instructable I'll explain how to setup and execute an interrupt in Clear Timer on. I'm thinking to use timer, but will it be suitable for my application? Instructables Arduino Timer InterruptsĪrduino Timer Interrupts: Timer interrupts allow you to perform a task at very specifically timed intervals regardless of what else is going on in your code. PinMode(outPin, OUTPUT) // sets the digital pin as outputĭigitalWrite(outPin, HIGH) // sets the pin onĭelayMicroseconds(50) // pauses for 50 microsecondsĭigitalWrite(outPin, LOW) // sets the pin off I tried this sample code but the 50us pulse shifted left and right in the oscilloscope. ![]() It seems like delayMicroseconds() is much easier for my application, but it is not very accurate. Then stop until the program receive other 3 values. When the timer reach c_value do something. When the timer reach b_value do something. When the timer reach a_value do something. 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 am making a program to accept three values (a_value, b_value and c_value). 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. for the 16 MHz clock on most Arduino boards 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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