An interrupt based quadrature encoder for the RP2040.
This simple OOP approach to an encoder is enabled by static variables and templates: The interrupt service routines (isrs) are called without a reference to their object. The static keyword is used to still allow access to object variables. Static variables are the same for all instances of a class. So we trick the compiler into creating a new class for each encoder using a template.
Instanciation may look somthing like this,
note that Quadrature_encoder<MY_DATA_PIN, MY_CLK_PIN> is the name of the class:
Quadrature_encoder<DATA_PIN, CLK_PIN> my_encoder = Quadrature_encoder<DATA_PIN, CLK_PIN>();
After construction call begin() during setup and count() to get the steps since the beginning.
end() usually must not be called.
Because the RP2040 can only have one gpio_isr the gpio_irq_handler is used to
allow one function call to be registered per pin.
This header creates an interface using a jump table, allowing the user to attach pin and core specific callback functions.
You may
#define DEBUG_IRQ_DURATION_PIN 11 //for example
To debug the duration of your ISR with a logic analyser.
This will switch the pin high during the ISR and low otherwise.
and
#define HIGHEST_INTERRUPT_PIN 15 //for example
To safe some memory in the jump table,
but disabling interrupts on pins higher than specified.
- Clone this repo e.g. to
myproject/include/RP2040-Encoder - Add the repo the
.gitmodulesfile as a submodule, adding:
[submodule "Encoder"]
path = include/RP2040-Encoder
url = https://github.com/tobiglaser/RP2040-Encoder.git
branch = main
- Tell CMake where to find the new include files,
adding this somewhere after
add_executable()inCMakeLists.txt:
# Add Encoder
target_include_directories(my_project PUBLIC include/RP2040-Encoder)
- Copy an example to your main.cpp and try it out.
Refer to Pico-FreeRTOS-Project-Template for a FreeRTOS template.
The approach using templates and static variables was inspired by zacsketches/Encoder.