Raspberry Pi Pico PIO - PIO Interrupts using MicroPython - Ep. 20 

When you go fast; you make twice as many mistakes per minute :-)

Thanks for the further explanation. As you may have gathered, I'm not a big fan of restrictions that MicroPython puts on interrupts. I like C better, and I'm enjoying assembly (yes, they said I was a little weird when I was growing up...lol). Thanks for watching!

You're welcome. Thanks for watching!

Thank you. Thanks for watching!

Glad it was helpful!

Thank you!

Thanks for the comments and suggestion. I hope to publish a bare metal assembly video on UART communications in the next week or so, It's not PIO but close. Thanks for watching!

Thank you. I found MicroPython very limiting when it came to Interrupts. I don't know how they would work for any UART application faster than 300 baud (OK, maybe that's a bit of a stretch, LOL). I have moved to assembly to handle interrupts and I'm very happy. It seems like both C/C++ and MicroPython impose time constraints on their interrupt handlers (probably because there is a lot more going on behind the scenes). However, with assembly, I can take my time; especially if that's the only interrupt in the system. Check out my Bare Metal troubleshooting video (ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-GyxlBpIZ28I.html). Thanks for watching!

I haven't played with neopixels yet, but at a frequency of 800 KHz, I don't see why you couldn't. With PIO you can process 125 million instructions per second, much more than needed for an 800 KHz signal. Good luck, and thanks for watching!

@@LifewithDavid1 Hi David! Thanks for your reply! What I couldn't find anywhere here on RU-vid (nor elsewhere at all) is a video / an instruction about reading data of custom protocols (neopixel in my case) via PIO and processing them with the main core. Could it work like this: ? State machine 0's only job would be to sense the neopixels reset code of a PIN_LOW for more than 80 microseconds: Set an IRQ set the x register to a value that could be decremented to 0 within 80 microseconds. decrement it with every cycle as long as the inputpin is low. if the signal becomes high before x is zero we jump to the top. if it's at zero we clear the irq flag to trigger : State machine 4 waits for the IRQ flag to be cleared. Then sets the x register to 31 and decrements it with every clock cycle that the input pin is sensed to be high. The frequency of this state machine is set in a way that 31 full cycles take roughly 800 Nanoseconds to distinguish between bit 1 or 0 being 300 or 600 nanoseconds long. If the input pin goes low the value of x (as a representation of how much time has passe) is stored in a register (but which one?!) Somehow I would need to get the first 96 measured timings to the main core to interpret them as a 1 or 0 depending on a threshold and translate them into an array of 6 x 16 bit integers for further use. Does that make any sense? Since I'm totally new to handling bits and Micropython in general I'm not really confident in getting the syntax and structure right And since there is no easy way to debug things happening inside a PIO I'd love to finde someone, who is interested in giving some sort of support. The implementation of this function would open up many possibilities to the Neopixel community. So any hints would be highly appreciated :-)

See my other reply. Good luck!

That's a great question. The only arithmetic function that PIO has is decrementing the X or Y register and that is in conjunction with a jump. So having PIO count the pulses directly is probably not in the cards. However, you could use PIO to monitor the encoder and have it trigger an interrupt when it sees a change in the encoder signal. The handler could update the motor position to a global variable that the main program could use as needed. Hope this helps. Good luck!

@@LifewithDavid1 thanks for an answer, but for this reason im using regular interrupt. What i will achieve using pio this way?

@@LifewithDavid1 silly though. If ill use dec function co count down the encoder. Since its 32 bit, its a lot of counts to be stored. What do you say?)

@@aleXelaMec PIO is not for everything. I'm not sure if you are using a single or two phase encoder, but PIO could do a little pre-processing, like de-bouncing or direction detection. If your main application is time critical, PIO could make the interrupt handler just a little faster. But for normal use, I would probably use regular GPIO interrupts.

@@LifewithDavid1 Got you. Program is not time consuming. it's an encoder counter on rp2040. my problem is that using mycropython sending data to display take more time than encoder readings, so I have to either move to C or try using two cores with a buffer. using regular interrupts now. But overall I like the idea of these modules even they are very limited. at least fun to play with ) Thanks

... I guess the logic is, if it can't decrement, that line 'gets skipped'. I do hope to get a great grasp of the Pi Pico; it's a nice unit.

Marc, This video might help: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-qegs8LGINww.html