Your welcome, and good luck with your project.

Could be that his bench top power supply and whatever was supplying power to the Pico have grounds that are close enough for it to work. But you're right, there really should be a common ground between the Pico and the ULN2003.

It's a matter of "endianism", in this case "little-endian". The first bit in a word that any word (even word of length 1, i.e. a bit) will definitely have is the lowest-order bit - the 1's column in a numeric representation. So that bit will take care of the GPIO line "right here", and anything beyond that (i.e. numerically in the higher powers of 2) can overspill to "further on". Regarding the driver board... it ¦might¦ be a 'courtesy' to give it a common ground, but it's not a logical necessity. The reason being [I am surmising based on previous investigation] that you can drive two phases, a "forwards" and a "backwards" (with an option of "nothing") with two driven voltage sources, e.g. GPIO lines: (1,0) can be forwards, (0,1) can be backwards, and (X,X) - for consistent X as either 1 or 0 - is no drive. Just have the driver board compare the two given signal voltages for an unambiguous input. It's similar to the idea of driving an LED between *two* GPIO lines, instead of as usual between one GPIO and the high or low supply rail. Do this twice - two independent channels - to get your four phases. How the electronics downstream inside the stepper motor chassis itself expands these four into a great many more physical phases for its actual windings is something I haven't pondered properly, though.

@@duncanwalduck7715 , not with these steppers, they are 4 phase plus a common. The ULN2003 is just 7 high current transistor switches, 4 of them are used for the stepper, the other 3 are redundant. (If they'd used the ULN2803 which has 8 switches they could've made 4 pairs, doubling the current capacity.) There really should be a ground wire from the Pico to the driver board.

r/rarecomplements

Unless the power used by both the motor and the Pico, my guess would be that at least one of the pins to the motor is always in a sinking-state and that's the GND connection. Not a good way, but probably just a small oversite on the maker's part.

I guess PC and power supply have common ground through power plug but that is pretty bad way to do it and quite dangerous.

@@bumbarabun Not really. It's actually perfectly fine, you may call it bad practice but in real life it will work.

@@tunahankaratay1523 perfectly fine? Yea have ungrounded power supply and burn USB ports on your PC or maybe motherboard as well. That does not sound fine for me.

Thanks :-) you just need to adjust the speed that the routine cycles through the movement pattern. Maybe adding a delay into the state machine (not a lot of registers left to work with though) or having a few state machines that run at different frequencies (wasteful but maybe ok if your only working with a few steppers) I think the Pico can have 8 state machines max, but I have not tested this.

I assume he takes the 5V from the pico supply line.

@@foorje I had a similar issue with one of my projects. I was powering all my external interface circuitry from my bench power supply and it all worked despite missing off the ground to the Pico. I actually wanted a floating interface supply - I found & removed a discrete (barely noticeable) link between 0V and ground on the bench PSU and I assume my PC's 0V (as appearing at the USB interface) is also grounded via the mains earth line. This "accidental" grounding should be avoided particularly on analogue circuits (I was using the ADC) where a "ground loop" will pick up all sorts of unwanted noise & interference.

Search for the Pico Micropython SDK (YT won't let me post the link) There is also info in the data sheet for the Pico and the C++ SDK.

Yes. You can write your own functions exactly as seen here or use the in-built library within the Arduino IDE (www.arduino.cc/en/reference/stepper). If your intention is to learn programming I'd experiment writing your own functions, however if you're attempting to build the motor into a project I'd recomend -> www.airspayce.com/mikem/arduino/AccelStepper/ as a library that can add acceleration/deceleration ramping allowing smoother, faster movements. If you're interested in writing your own accel/decel code, ww1.microchip.com/downloads/en/appnotes/doc8017.pdf is a good place to start for the base theory. Are you referring to the driver or motor being small? In either case there are smaller (better) versions of both. A good driver is www.digikey.co.uk/product-detail/en/trinamic-motion-control-gmbh/TMC2208-SILENTSTEPSTICK/1460-1201-ND/6873626 (hunt around for the best price).

Thanks :-) I should have talked about that in the video really, all you need to do is reverse the movement pattern to change the direction

Thanks :-), that sounds like a very interesting automation project, good luck with it!

wouldn't the heavy machines disturb the radiosignals ?

@@jyvben1520 Yes, that is a distinct possibility and something that I plan on testing extensively to see how many lost radio packets there are both with and without the machine running. I suppose it depends to some extent on the quality of the machines (motor suppressor) AND the quality of the radios. But thanks for pointing it out.

3 main options, you can control the GPIOs on the pi using shell script, C++ or python. Probably best searching for separate tutorials on that. Main thing here is to learn to use the PIO state machines on the Pico microcontroller. The only reason he is demoing the programming on a raspberry pi rather than using the pi to control the motor, is because setting up for Pico programming without a pi/linux is currently a bit "involved".

You cannot drive enough current by GPIO.

@@bumbarabun I think by controller they meant without micro controller rather than without the stepper interface board... Although I guess that take on things might be the intention... I guess it is ambiguous

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