class Counter – pulse counter¶
Counter implements pulse counting by monitoring an input signal and counting rising or falling edges.
Minimal example usage:
from machine import Pin, Counter
counter = Counter(0, Pin(0, Pin.IN)) # create Counter for pin 0 and begin counting
value = counter.value() # retrieve current pulse count
Availability: ESP32
Constructors¶
- class machine.Counter(id, ...)¶
Returns the singleton Counter object for the the given id. Values of id depend on a particular port and its hardware. Values 0, 1, etc. are commonly used to select hardware block #0, #1, etc.
Additional arguments are passed to the
init()
method described below, and will cause the Counter instance to be re-initialised and reset.On ESP32, the id corresponds to a PCNT unit.
Methods¶
- Counter.init(src, *, ...)¶
Initialise and reset the Counter with the given parameters:
src specifies the input pin as a machine.Pin object. May be omitted on ports that have a predefined pin for a given hardware block.
Additional keyword-only parameters that may be supported by a port are:
edge specifies the edge to count. Either
Counter.RISING
(the default) orCounter.FALLING
. (Supported on ESP32)direction specifies the direction to count. Either
Counter.UP
(the default) orCounter.DOWN
. (Supported on ESP32)filter_ns specifies a minimum period of time in nanoseconds that the source signal needs to be stable for a pulse to be counted. Implementations should use the longest filter supported by the hardware that is less than or equal to this value. The default is 0 (no filter). (Supported on ESP32)
- Counter.deinit()¶
Stops the Counter, disabling any interrupts and releasing hardware resources. A Soft Reset should deinitialize all Counter objects.
- Counter.value([value])¶
Get, and optionally set, the counter value as a signed integer. Implementations must aim to do the get and set atomically (i.e. without leading to skipped counts).
This counter value could exceed the range of a small integer, which means that calling
Counter.value()
could cause a heap allocation, but implementations should aim to ensure that internal state only uses small integers and therefore will not allocate until the user callsCounter.value()
.For example, on ESP32, the internal state counts overflows of the hardware counter (every 32000 counts), which means that it will not exceed the small integer range until
2**30 * 32000
counts (slightly over 1 year at 1MHz).In general, it is recommended that you should use
Counter.value(0)
to reset the counter (i.e. to measure the counts since the last call), and this will avoid this problem.