class TimerWiPy -- control hardware timers¶
注釈
This class is a non-standard Timer implementation for the WiPy.
It is available simply as machine.Timer
on the WiPy but is named in the
documentation below as machine.TimerWiPy
to distinguish it from the
more general machine.Timer class.
Hardware timers deal with timing of periods and events. Timers are perhaps the most flexible and heterogeneous kind of hardware in MCUs and SoCs, differently greatly from a model to a model. MicroPython's Timer class defines a baseline operation of executing a callback with a given period (or once after some delay), and allow specific boards to define more non-standard behavior (which thus won't be portable to other boards).
See discussion of important constraints on Timer callbacks.
注釈
Memory can't be allocated inside irq handlers (an interrupt) and so
exceptions raised within a handler don't give much information. See
micropython.alloc_emergency_exception_buf()
for how to get around this
limitation.
Constructors¶
-
class
machine.
TimerWiPy
(id, ...)¶ Construct a new timer object of the given id. Id of -1 constructs a virtual timer (if supported by a board).
Methods¶
-
TimerWiPy.
init
(mode, *, width=16)¶ Initialise the timer. Example:
tim.init(Timer.PERIODIC) # periodic 16-bit timer tim.init(Timer.ONE_SHOT, width=32) # one shot 32-bit timer
Keyword arguments:
mode
can be one of:TimerWiPy.ONE_SHOT
- The timer runs once until the configured period of the channel expires.TimerWiPy.PERIODIC
- The timer runs periodically at the configured frequency of the channel.TimerWiPy.PWM
- Output a PWM signal on a pin.
width
must be either 16 or 32 (bits). For really low frequencies < 5Hz (or large periods), 32-bit timers should be used. 32-bit mode is only available forONE_SHOT
ANDPERIODIC
modes.
-
TimerWiPy.
deinit
()¶ Deinitialises the timer. Stops the timer, and disables the timer peripheral.
-
TimerWiPy.
channel
(channel, **, freq, period, polarity=TimerWiPy.POSITIVE, duty_cycle=0)¶ If only a channel identifier passed, then a previously initialized channel object is returned (or
None
if there is no previous channel).Otherwise, a TimerChannel object is initialized and returned.
The operating mode is is the one configured to the Timer object that was used to create the channel.
channel
if the width of the timer is 16-bit, then must be eitherTIMER.A
,TIMER.B
. If the width is 32-bit then it must beTIMER.A | TIMER.B
.
Keyword only arguments:
freq
sets the frequency in Hz.period
sets the period in microseconds.
注釈
Either
freq
orperiod
must be given, never both.polarity
this is applicable forPWM
, and defines the polarity of the duty cycleduty_cycle
only applicable toPWM
. It's a percentage (0.00-100.00). Since the WiPy doesn't support floating point numbers the duty cycle must be specified in the range 0-10000, where 10000 would represent 100.00, 5050 represents 50.50, and so on.
注釈
When the channel is in PWM mode, the corresponding pin is assigned automatically, therefore there's no need to assign the alternate function of the pin via the
Pin
class. The pins which support PWM functionality are the following:GP24
on Timer 0 channel A.GP25
on Timer 1 channel A.GP9
on Timer 2 channel B.GP10
on Timer 3 channel A.GP11
on Timer 3 channel B.
class TimerChannel --- setup a channel for a timer¶
Timer channels are used to generate/capture a signal using a timer.
TimerChannel objects are created using the Timer.channel() method.
Methods¶
-
timerchannel.
irq
(*, trigger, priority=1, handler=None)¶ The behavior of this callback is heavily dependent on the operating mode of the timer channel:
- If mode is
TimerWiPy.PERIODIC
the callback is executed periodically with the configured frequency or period. - If mode is
TimerWiPy.ONE_SHOT
the callback is executed once when the configured timer expires. - If mode is
TimerWiPy.PWM
the callback is executed when reaching the duty cycle value.
The accepted params are:
priority
level of the interrupt. Can take values in the range 1-7. Higher values represent higher priorities.handler
is an optional function to be called when the interrupt is triggered.trigger
must beTimerWiPy.TIMEOUT
when the operating mode is eitherTimerWiPy.PERIODIC
orTimerWiPy.ONE_SHOT
. In the case that mode isTimerWiPy.PWM
then trigger must be equal toTimerWiPy.MATCH
.
Returns a callback object.
- If mode is
-
timerchannel.
freq
([value])¶ Get or set the timer channel frequency (in Hz).
-
timerchannel.
period
([value])¶ Get or set the timer channel period (in microseconds).
-
timerchannel.
duty_cycle
([value])¶ Get or set the duty cycle of the PWM signal. It's a percentage (0.00-100.00). Since the WiPy doesn't support floating point numbers the duty cycle must be specified in the range 0-10000, where 10000 would represent 100.00, 5050 represents 50.50, and so on.