Learn how to use both cores on your Raspberry Pi Pico in C using the Linux SDK! Multi core programming makes your projects more powerful! By using both processor cores on the ARM RP2040, we have the potential to make our code 100% more efficient. Check out this and more embedded programming topics on my channel!
Make sure you check out my C/C++ SDK setup example before watching this video: https://www.youtube.com/watch?v=JhajoAyP8e4
Source code available here: https://www.github.com/lowlevellearning/multi-core-code
Chapters:
0:00 Intro
0:18 What is Multicore?
0:50 How Do RP2040 Cores Communicate?
2:15 Lets Code!
7:39 Outro
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the raspberry pico rp2040 is an arm cortex m0 based microprocessor equipped with two cores in this video i’ll show you how to write code for the raspberry pico that uses a second core on the processor using the second core enables you to make your picot projects twice as powerful by using a completely separate thread of execution to talk about doing multi-core programming we first need to define what the word core means a core is a functional unit on the processor capable of executing program code by having multiple cores on a processor you can execute multiple segments of code at the same time whenever we write code for the raspberry pico for example core zero the first core executes the code the second core is on standby never doing anything here you see a depiction of two cores each core is separately running its own code completely independently they have separate program code and separate memory space there are cases however where the course can share program code and memory space sharing code is not problematic as fetching code is a read instruction and it does not create a race condition however sharing the same locations for data is problematic as it creates a possibility for a race condition to exist where mutual accesses to the memory is not assured so if the cores aren’t supposed to share memory directly then how did the course communicate well the masterminds at raspberry pi figured this out and created two separate fifos or first in first out structures to act as a mechanism for communicating between the cores only one fifo is writable by core zero and only one fifo is writable by core one this way no core is ever writing to the same location at the same time in this example core zero has some memory it needs to communicate to core one for some kind of processing instead of writing that memory directly into core one’s memory space which could introduce a race condition core zero uses its writable fifo to push that data to core one core one does its processing and then uses its fifo to get that process data back to core zero core zero could have been executing other tasks while waited for core one to finish processing this process of using fifo’s to pass data around prevents weird cases where core zero is reaching into core one’s memory or vice versa so with that being said let’s write some code to make this happen in c okay so here we are in my linux build environment um if you haven’t watched my previous video on how to set up a cmake build environment for the raspberry pico c sdk please go watch that it’ll make this video much more easy to digest i know i keep beating this up but i do have to say i could not have done this tutorial if i didn’t have the raspberry pi pico c sdk document in front of me the entire time they do a very good job of documenting all the functions i’ll be using today in the tutorial so after this tutorial go give this a read and see what other trouble you can get yourself into anyway back to the code um so over on the right we’re going to be writing the code that’s going to go onto our raspberry pi pico um so this is a multi-core video so the first thing we need to do is initiate the second core uh and the way we do that with raspberry pi pico is first we have to pound the pico slash multi-core dot h library what that does is it includes the library of code that raspberry pi has produced to enable us to do multi-process programming on the raspberry pi pico next we need to tell the raspberry pi pico to launch code on its second core and just to prevent any confusion um the second core is called core one just so you’re aware so the code starts this code will start in court zero and the rest of the code that we launch on the second core will be in core one just so we’re all on the same page we’re gonna call this function and we’re gonna call it on the function name that’s going to get ran by the second core and we’re gonna call that second core code and then we have to define a function we’re going to define it as a void second core code and then whatever we write in this area is going to get ran on the second core so that was pretty fast
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