Getting Started with Multicore Programming on the Raspberry Pi Pico
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- Опубликовано: 14 июл 2024
- This video covers how to create a simple multicore program which uses both cores on the Raspberry Pi Pico. We use a Visual Studio Code project to program the brand-new Raspberry Pi Pico microcontroller board. We created a program where one core uses the analogue to digital converter in the Pico to read the internal temperature of the RP2040 and sends this data to another core to output the temperature of the chip to a windows machine over a USB serial interface.
This video provides a conceptual overview of multicore (dual core) operation on the Raspberry Pi Pico. It also explains how to configure interrupts to correctly handle the sending and receiving of data between cores. We briefly discuss how to set up the analogue to digital converter (ADC) to read the onboard temperature of the RP2040 chip.
The source code for this project (and a written article version) is available here: learnembeddedsystems.co.uk/ba...
Timestamps
00:00 - Introduction
00:33 - Why use a Multicore Program?
01:46 - How do Multicore Programs Work?
03:40 - Creating a Visual Studio Code Project
04:29 - Writing CMakeLists File
05:30 - Writing C File
09:45 - Conclusion
If this video helped you, please consider leaving a like and subscribing, thank you!
To see my other videos on the Raspberry Pi Pico, check out the playlist here: • Pico Tutorials
You can find more embedded systems tutorials and projects on my website learnembeddedsystems.co.uk
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Hands down the BEST coding video I've ever seen. Your narrative keeps up perfectly with your coding, you explain everything perfectly and you don't have any time-wasting moments in the video where EVERYONE ELSE DOES because they think that we want to sit here and watch them correct their mistakes while they mumble to themselves. NOT YOU! You NAILED IT! NICE WORK!
Agreed. It’s very nicely put together. Controllers Tech videos are also packed with useful info and presented well. (Not everyone will appreciate the presenter’s artificial voice, but the quality content and thoughtful presentation make them worth a look.)
Short, straightforward, to-the-point. I like it. Thanks! 👍
Glad it was helpful!
This is exactly what I was looking for
Great video!! Very informative with how cores work and how to get things working. Nice work!
Thanks for the support! Glad you it informative!
Wow, what a nice channel, I'm glad I found it! This video was super helpful
Thank you! Glad it was helpful!
Excellent video, thanks I will keep following
Awesome, thank you!
Nice intro. Thank you.
Thanks for doing this in C/C++. There are copious amounts of micropython examples out there for the Pico, but very few useful ones in C/C++. Nice pacing, editing and focus.
Thank you! We will focus on C mostly with this channel!
keep it up man nice work
real helpful thank you
Thank you! Glad I could help
Great video. It would be helpful if you used a larger font on VS Code or encoded the video at a higher bit rate so the text was more readable. Thanks.
Thanks for the feedback David, I will be sure to fix this in my upcoming videos!
yeah, stopped viewing just listening, video text too small, website is fine
@@jyvben1520 Thank you for the feedback, still new to this tutorial/youtube game so very useful to know how to improve! I have already increased the font size in my upcoming videos. Happy to hear you found the website useful!
I thought the text size was just fine but the bright white backgrounds of the animations were blinding, maybe a texture a dark mode style would be better? Awesome video.
@@MagicPlants Thank you for your feedback, I will look into creating a darker theme for my new videos! Much appreciated :)
Another great video. I did have to add sleep_ms(1000); after stdio_init_all(); in main to get the program to function correctly. I am looking forward to seeing multi core with the freeRTOS. Thanks!
Very nice =) Thanks =)🙂
Thanks. In 25 years of firmware coding I always assumed I'd need multithreading at some point but it just hasn't happened; PC software's a different matter of course. So I come to the Pico wondering what scenarios justify the overhead. Most multicore MCUs have cores specialized for different purposes - eg M0/M4 - which makes sense. I'm thinking it's gonna need some careful design to get the most out of two symmetrical cores. But they're welcome!
Although I have now Pico, I found it realy interesting!!
Glad to hear that you found this video interesting!
I'm surprised you didn't get a watchdog exception for doing so much during an interrupt, unless the Pico SDK doesn't check for that.
For the ESP32, if you spend too much time in an interrupt, you'll get a panic and crash. That happened to me trying to use an interrupt handler in ESP32 to process data when available from an external ADC that calculates AC RMS from a current sensor.
A better method of handling data transfer signaled by an interrupt is to tell the main program in core1 through a flag that there's data available, or have the interrupt populate a buffer defined in the core1 code.
But I realize this is just to get our feet wet using multi-core, FIFO, and interrupt.
Interesting illustration, but normally you’d want to do the bare minimum in an interrupt handler, and defer calculations and printing to a foreground task on the same core.
In my experience one should never do blocking calls directly in interrupt handlers.
super!!!!!
Super interesting! Nice to see the whole project being created too rather than just opening Arduino IDE. Although I’m guilty of that I suppose as I just let CubeMX do all the setup 😝
How have you found the discoverability with the pi pico? Is all of this based on examples they provide and is it easy to dig into the HAL files and find what you need or is it provided as a compiled library that you can’t view?
The Pico c/c++ SDK is pretty well documented, and so most of the examples I present in these videos will follow a similar form to the examples so people can jump from these videos into the documentation and vice versa. I will have a few videos (soon-ish) not using the SDK.
In terms of discovery, you can poke around the HAL (or SDK as RPi foundation like to call it) all you like, it is not compiled until you compile it, but finding what you are looking for may take a little time. You can have a look at the Github here: github.com/raspberrypi/pico-sdk
Is there a race condition between checking queue status and clearing the queue interrupt?
Thanks for the video. What is the size of the FIFO buffer?
It would have been helpful if you also show how your temperature sensor was connected to the Pico
Two cores should be nice for DSP or audio analysis. One core reads ADC and one performs FFT.
That is a perfect example of off-loading a more demanding task onto the second core! I will look into this and perhaps make a video of your example
@@LearnEmbeddedSystems Nice! Maybe share your code if the video is online? ;D
Would reading the ADC directly take more CPU than reading from the FIFO? I wouldn't have thought it would.
Is it possible to simulate multithreading on core1(or even core0) by changing and switching between the interrupt handlers?
I have a question. How can you send the value of a variable that has been defined in the core1 back to core0? I've been trying to send the temp variable calculated in the core1 back to the core0 with the "multicore_fifo_push_blocking(temp);" function but it doesn't appear to be working.
Hello, I do not understand the conversion factor : const float conversion_factor = 3.3f/(1
Can you please make a video on how to make sure that a specific thread is executed in hard real-time? For example a time of 54 micro seconds? How can this be achieved? With a condition variable?
Precise timing will require a real time operating system (RTOS). There has already been a port of freeRTOS to the Pico, and I will eventually get round to making a video on it! If you can't wait then here is a link to the freeRTOS port github.com/PicoCPP/RPI-pico-FreeRTOS
What would the micropython code for this be?
would be nice to see how to use pico with linux developing and FreeRTOS
Nice video however I would advise rather using queues and not the intercore fifos, as those are usually required to be reserved if you implement any real multicore program.
Also usage of floats seems very unnecessary, fixed point would have been more than enough, especially in an ISR where you usually want to keep cycles to a minimum.
I have my dev machine set up exactly the same way as "Learn Embedded Systems" The issue I am having with setting up the multi-core is that I am getting errors during the CMake configuration process. I get the following errors:
[cmake] TinyUSB available at C:/Pico/pico-sdk/lib/tinyusb/src/portable/raspberrypi/rp2040; adding USB support.
[cmake] Compiling TinyUSB with CFG_TUSB_DEBUG=1
[cmake] -- Could NOT find Doxygen (missing: DOXYGEN_EXECUTABLE)
[cmake] CMake Error at C:/Pico/pico-sdk/src/rp2_common/pico_stdlib/CMakeLists.txt:26 (set_target_properties):
[cmake] set_target_properties Can not find target to add properties to: multicore
[cmake] Call Stack (most recent call first):
[cmake] CMakeLists.txt:18 (pico_enable_stdio_usb)
[cmake]
[cmake]
[cmake] CMake Error at C:/Pico/pico-sdk/src/rp2_common/pico_stdlib/CMakeLists.txt:22 (set_target_properties):
[cmake] set_target_properties Can not find target to add properties to: multicore
[cmake] Call Stack (most recent call first):
[cmake] CMakeLists.txt:19 (pico_enable_stdio_uart)
[cmake]
[cmake]
[cmake] ELF2UF2 will need to be built
[cmake] -- Configuring incomplete, errors occurred!
[cmake] See also "C:/Pico/pico-projects/build/CMakeFiles/CMakeOutput.log".
[cmake] See also "C:/Pico/pico-projects/build/CMakeFiles/CMakeError.log".
How possible i would it be to use picos in a computing cluster?
I think it would certainly be possible but it's actual use might be quite limited. These microcontrollers perform well performing fast functions like I/O but don't have particularly much compute horsepower. So as an exercise it would certainly work but in terms of functionality? I think it would be outperformed by the most basic Raspberry Pi cluster.
Hope this helps!
Can it be done with the Arduino IDE too, or are we limited to one core?
Answering my own question; earlephilhower's arduino-pico, on github, allows the use of both cores. You have the normal setup() and loop() for core 0, and an optional setup1() and loop1(), for core 1.
You can install support from there, or by copying the .json link into the settings of the Arduino IDE, then use the Boards Manager, on the Tools->Board menu.
Posting the link got my comment blocked, so you'll have to google it, or search on github.
Why would you use the FIFO buffer when you can just use global variables?
The FIFOs do simply quite a wide range of possible applications.
The introduction part of the video seems to rather imply the FIFO buffers are the only way to do multi-core on the Pico! Surely not?
Good video, but i confused , how can we talk about a multi-core application if there is an external controller (or interrupt)? You can't do two operations at once if you have a controller or loop .In my opinion, a serial processor cannot operate two operations independently of each other. If it's working, *it doesn't return any data to you.* anyway, thanks for sharing, have nice day !
The interrupt was set on Core 1, so it won't have any effect on Core 0. You *can* do two operations at once *if you have two cores* - that's the point of having multiple :D
what is missing with raspberry pico is a good IDE to develop with like arduino has
PlatformIO
Mate make the code bigger in the IDE; I can't see a thing.
Thank you for your feedback - I have already implemented this in my latest (and upcoming) videos! Appreciate the feedback :)
How to debug this thing ??
That's the 64 million dollar question.
Dude - you have a "printf" in an ISR!! it's only because this is such a trivial example that it works at all. ISRs should be short and sweet. Get the data and put it into a queue for the "main" loop for the core to handle.
Why use dual core? The alternative is to only use half of the CPU you just paid for.
Your font size is too small.
2:09 "Memory IS ram!"
All RAM is memory, but not all memory is not RAM.
calling a "printf" inside a interrupt handler is not really good practice. Keep is short, like raising a flag, that's it.
It's quite surprising to me that this would work at all. I would have thought it likely that the USB output would need interrupts to work and usually interrupt systems don't, at least by default, allow interrupts to nest.
Is there a similar video but with FreeRTOS on the pico ? The ESP32 has its own slightly modified SMP enabled version of FreeRTOS i was hoping that the pico also has some such implementation
Having similar function calls like the ESP-IDF for the pico would make life a lot easier to write multi-core RTOS applications. Especially with the pico W . @LearnEmbeddedSystems