MicroPython #4 - PWM, ADC, Timers & Interrupts 

Cheers David!

Ok, I was able to confirm my suspicion - which is positive in this case ... ;) The hardware-timer that you introduced in this video is even working while the REPL is blocked with something else e.g. a time.sleep(5). I kind of expected that, but I wasn't sure - now I am. Cool stuff! My LED is blinking a friendly "Thank you and stay healthy during those difficult times!" :)

Awesome, thanks for letting me know!

Thanks heaps Santiago!

Thanks Paul. Yeah I am constantly surprised by how easy and intuitive it is to code in. Loving it!

Cheers John! I still don't know much about Python/MicroPython but I'm learning as I am teaching!

Glad to hear Adam! Me too!

Cheers mate! How's your coding going? Got any progress to share?

@@UnexpectedMaker nope, not a sausage to share sadly, Ive played with neopixel, (always fun) but progress is steady and as soon as I finish "Doom" on my ESP8266 you'll be the first to no !

The difference in the "is" behavior could be implementation/version dependent. I believe that, by definition, "is" returns true if the two id()s are the same. "is" is supposed to only be for checking to see if the two objects being compared are (pointing to) the same object. As you noted, by virtue of id() returning the same value, they are referencing the same object. The reason why Seon's "is" demo results are different than yours could be changes in the implementation between whatever version and his. If you remember/know, Python strings are immutable, so in cases where the runtime makes the effort to see if there's already a string with the same value ("hello" in stra, in this case), it's safe for strb to also point to it, because it can't be changed through any references to stra. An implementation may choose to create another copy of "hello" in memory for strb and point to it, rather than double-teaming the perfectly valid/safe copy of "hello" made first for stra. This is a memory optimization --at the expense of looking for a usable, equivalent string with the same contents at object-creation time. Bottom line, this implementation-dependent "is" comparison is unreliable, for just this reason. "is" should only be used to compare two object references where one reference was derived from the other. For example, a technically correct demonstration of is would be: stra="hello", strc="foo", if (blah): strb=strc, ..., strb=stra, stra is strb -> True. The results of "is" for Seon's demonstrated case are either undefined in the language definition, or the semantics changed from one version to the other (unlikely). So, technically doing what Seon did in his demo is demonstrating a case of undefined behavior per the language spec (if my suspicion/explanation is in fact correct).

Same, somehow micropython is noticing that my two strings contain the same text so is optimising them to a single object. >>> stra = "hi" >>> strb = "hi" >>> (stra == strb) True >>> (stra is strb) True >>> inta = 1 >>> intb = 1 >>> (inta == intb) True >>> (inta is intb) True >>> id(stra) 4410 >>> id(strb) 4410 >>> id(inta) 3 >>> id(intb) 3 >>>

Hahahaha! Don't feel any pressure to try it out ;)

Ha! rshell really rocks... esp using rsync. I have that on my list of things to showcase, and VCS + rsehll removes the need for any other IDEs ;)

You spend a good deal of time recording and editing these outstanding tutorials. Have a cup of java on me!

Thanks Danny. I have a lot of more general stuff to cover still before I look at specific things like that.

Woohoo, you got a PyBoard D? Damien has made an amazing board! I'm just using the Python extension in VSC and rshell to talk to my TinyPICO.

@@UnexpectedMaker Unfortunately this pyboard V1.1 is not genuine. But now that I looked his website, the D version seems pretty good! My long time goal is to make a model rocket flight computer. I'm fairly new to programming so this micropython looks like easier way to do that compared to c++. It would be awesome to make thrust vector control to gimbal the motor from accel/gyro data.

Thanks!

Thanks! Yup, any ESP32 board will work, though without the extra PSRAM like on the TinyPICO, you'll only have about 120KB, but that's enough for a lot of stuff.

No idea mate, sorry. Google is a better place to answer questions for niche stuff like that. Cheers.

Yes, the machine module in each hardware port uses the correct default ADC resolution for its hardware, but it's a lot more complicated than that. The ESP32 has a sliding resolution that you can change, and though it might default to 12bit, (0-4095) it's only a 0v-1v range, so if you change the range to 0-3.3V, you lose resolution. It's the same with PWM, if when you change the frequency, your available duty cycle range is altered too. Both of these topics were beyond the scope of this video as they really require people to read and understand the capabilities of the hardware.

@@UnexpectedMaker thamks for the adc info and the map function. The adc info is disappointing though I could use a voltage splitter to knock down the incoming signal. Sensors I use are normally 0-4.8v

Yes, a voltage divider is all that is needed to convert 0-4.8v to 0-1v.

@@MicheleHjorleifsson uh... depends on your resistor value choices. Using an op-amp could be a better solution, unless you understand what all of the impedances involved are. But for some/many cases a voltage divider might be just fine.

Well, like in c++ delay(), time.sleep() or time.sleep_ms() are blocking calls, so they halt all execution during the sleep. If you code is ok with being halted like that, a simple sleep() is fine, but of you need things to happen in a periodic fashion without halting execution of the rest of your code, timers are perfect.

Makes perfect sense. Thank you!

you have to create a boot.py, and press the botton boot... Use Thonny is much more easy.

Well, I figured it out...I thought what the hell let me try running this through REPL and see if it's crashing. It's not, just PyCharm. Ignored the error and up and running.

Yay for your new TinyPICO! MicroPython deliberately doesn't ship with every library built into the firmware... or it would be bloated with stuff most people don't need. You need to add the libraries you need to the filesystem on the TinyPICO to use them. Check out github.com/tinypico/tinypico-micropython for examples and libraries

@@UnexpectedMaker OK, this makes since. Still new to this. That worked Thank you

There is no Map command in MicroPython, but a map is simply this... def valmap(x, in_min, in_max, out_min, out_max): return int((x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min)

Soon :-)

Pin.IN, Pin.PULL_UP, Pin.PULL_DOWN docs.micropython.org/en/latest/library/machine.Pin.html#machine-pin

Thank you!!!!!

All of my new board designs are using USB-C, though Micro-B is still more popular - for now ;)

​@@UnexpectedMaker I hand soldered your tinypico board this week as a personal challenge (and because I have too much time on my hands from this virus) and it all works! :D it's an awesome design, good job!

Which part @m sherwood? I'm not sure what you mean.

@@UnexpectedMaker The tinypico play shield. I dont find it on the site. Please link me? And Thank you for the great tutorials

www.tinypico.com/shop