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diff --git a/docs/tutorial/timer.rst b/docs/tutorial/timer.rst deleted file mode 100644 index fee01e17b7..0000000000 --- a/docs/tutorial/timer.rst +++ /dev/null @@ -1,114 +0,0 @@ -The Timers -========== - -The pyboard has 14 timers which each consist of an independent counter -running at a user-defined frequency. They can be set up to run a function -at specific intervals. -The 14 timers are numbered 1 through 14, but 3 is reserved -for internal use, and 5 and 6 are used for servo and ADC/DAC control. -Avoid using these timers if possible. - -Let's create a timer object:: - - >>> tim = pyb.Timer(4) - -Now let's see what we just created:: - - >>> tim - Timer(4) - -The pyboard is telling us that ``tim`` is attached to timer number 4, but -it's not yet initialised. So let's initialise it to trigger at 10 Hz -(that's 10 times per second):: - - >>> tim.init(freq=10) - -Now that it's initialised, we can see some information about the timer:: - - >>> tim - Timer(4, prescaler=624, period=13439, mode=UP, div=1) - -The information means that this timer is set to run at the peripheral -clock speed divided by 624+1, and it will count from 0 up to 13439, at which -point it triggers an interrupt, and then starts counting again from 0. These -numbers are set to make the timer trigger at 10 Hz: the source frequency -of the timer is 84MHz (found by running ``tim.source_freq()``) so we -get 84MHz / 625 / 13440 = 10Hz. - -Timer counter -------------- - -So what can we do with our timer? The most basic thing is to get the -current value of its counter:: - - >>> tim.counter() - 21504 - -This counter will continuously change, and counts up. - -Timer callbacks ---------------- - -The next thing we can do is register a callback function for the timer to -execute when it triggers (see the [switch tutorial](tut-switch) for an -introduction to callback functions):: - - >>> tim.callback(lambda t:pyb.LED(1).toggle()) - -This should start the red LED flashing right away. It will be flashing -at 5 Hz (2 toggle's are needed for 1 flash, so toggling at 10 Hz makes -it flash at 5 Hz). You can change the frequency by re-initialising the -timer:: - - >>> tim.init(freq=20) - -You can disable the callback by passing it the value ``None``:: - - >>> tim.callback(None) - -The function that you pass to callback must take 1 argument, which is -the timer object that triggered. This allows you to control the timer -from within the callback function. - -We can create 2 timers and run them independently:: - - >>> tim4 = pyb.Timer(4, freq=10) - >>> tim7 = pyb.Timer(7, freq=20) - >>> tim4.callback(lambda t: pyb.LED(1).toggle()) - >>> tim7.callback(lambda t: pyb.LED(2).toggle()) - -Because the callbacks are proper hardware interrupts, we can continue -to use the pyboard for other things while these timers are running. - -Making a microsecond counter ----------------------------- - -You can use a timer to create a microsecond counter, which might be -useful when you are doing something which requires accurate timing. -We will use timer 2 for this, since timer 2 has a 32-bit counter (so -does timer 5, but if you use timer 5 then you can't use the Servo -driver at the same time). - -We set up timer 2 as follows:: - - >>> micros = pyb.Timer(2, prescaler=83, period=0x3fffffff) - -The prescaler is set at 83, which makes this timer count at 1 MHz. -This is because the CPU clock, running at 168 MHz, is divided by -2 and then by prescaler+1, giving a freqency of 168 MHz/2/(83+1)=1 MHz -for timer 2. The period is set to a large number so that the timer -can count up to a large number before wrapping back around to zero. -In this case it will take about 17 minutes before it cycles back to -zero. - -To use this timer, it's best to first reset it to 0:: - - >>> micros.counter(0) - -and then perform your timing:: - - >>> start_micros = micros.counter() - - ... do some stuff ... - - >>> end_micros = micros.counter() |