Raspberry Pi3 GIPO & Single axis

Hello ,every one this is my first post here.
Im total noob in LinuxCNC configuration. I know about this for good 10 years but never had a chance to play with it.
Now i finaly got some hardware , and i have an idea of making my life easier by using LinuxCNC on raspbery pi3 with touch screen.
Idea is to use Raspberry pi to run one axis , and have a DRO type of screen. I have a SC5780 stepper driver with stepper that has encoder and brake on it self. As i really don't know where to start. Im asking here. Can i just drive the driver directly from the RPI GIPO ?

I have managed to install LinuxCNC on to the raspberry Pi using this tutorial.

wiki.linuxcnc.org/cgi-bin/wiki.pl?RPi3BPreemptRT#buildhalgpio

And by some reading and playing managed to find this link to enable the working of the GPIO

erste.de/linuxCNC_raspberry_PI4.html


But im stuck for now , and need some guidance to where to go next after the fist install , and how to create single axis display - and how to even create the nesecery HAL and INI files to run only one stepper motor with brake.

Any help would be appreciated , and i hope i have posted this into the correct topic.

Thank you in advance , Stephan!

I have used the script from the first link to install the Linuxcnc , so the installed version is 2.9.0 ... (newest version i think?).

The problem is that my hal that im using is telling me im "pumping" step signal to the PIN 5 for the Y axis - but using my oscilloscope i do not get any signal.

I have tried to probe all of the GIPO pins to make sure that the HAL config and GIPO driver do not spit out the data on some different pin. But in no avail.

As i see that ppl have managed to run 3 axis mini mills - i really don't see any reason i would not manage to run only one axis.

My reasoning is to learn the linux software and configuration on this simple system so in the long run it will be easier to configure my future DIY mill.

I have watched few youtube videos to get the grasp on the basics ...

Do you maybe have any good links to HAL tutorials i should watch? Or read?

As im still quite noobish in understanding the HAL code to generate one axis.
I don't ask for full solutions just a nudge in the right direction or good pdf/video i need to watch to "get it"

Learning all of this stuff is the fun part!

Yes i understand that this is special hard way to make something - but not to learn. As for every little error i have to read the man files ...
(And if i get it to work like this - im sure it will work on simpler configurations (Parallel port or some kind of IO PCI Card ...)


I just copied my last two configurations i play with yesterday - as im currently at work - but using vpn to access my system at home - am not sure what changes are currently active.

But in general this two set of files were used to try to run GPIO ... I have tried to run step config just to get the feeling for generated files.As for simple one to two axis systems or some kind of a HMI panels for machines i see linux cnc as a great system for this type of configuration.

I was hoping to get the first blank configuration to gather some more know how.

Ps. I will watch this series on YouTube - to help me some in understanding the basics of logic

After some playing around and goofing in side hal files. I found few stupid typo mistakes. I managed to get some kind of output from the GPIO pin 3 yesterday. But it looks jerky on my oscilloscope and not that usable i think. I am attaching this half working hal and ini file.

I have tried to home the axis by clicking home ,and activating the GPIO pin 11 but to no avail. Really need some more reading and watching time on basics of configuration.

I have attached the video of the captured signal with oscilloscope, as for now im not willing to attach this to the stepper motor driver until im sure the signal is ok.

www.dropbox.com/s/dvqs8k88387c6fv/Video.avi?dl=0

Any advice on reading material , or video material would be highly appreciated!

Here is a working config. Some caveats: I only tested the x and y motion; I didn't test any inputs.
I do have a pair of NEMA 23 motors spinning, powered by Trinamic TMC2209 stepsticks. I think good drivers are a key part to getting good motion with the limited step rate from software. These drivers turn step information into sine wave "steps." They can even do 1/4 pulses per step, meaning they will run a full 360deg electrical commutation with one step signal. This can raise step size to machine positioning accuracy requirements.

Note that the pin mask section refers to the Broadcom GPIO numbers, whereas hal_pi_gpio.pin.-N-in/out refer to the raspberry pi header PIN numbers on the board.

For example, GPIO2 is used as output for the x axis step pulses and it is physically located on pin3 on the pi header.
Thus:
the bit mask masks gpio pin 2 as output
Xstep is the net or "wire" that connects the step generator to header pin 3

The above HAL code is located in two different files, presumably to make the HAL system more modular.

I started this config from the parport stepper config in the samples, then I replaced all the parport IO section with relevant parts from the hal_pi_gpio_demo.hal.

If your latency is bad, the step timing will be equally bad.

Todd wrote:

If your latency is bad, the step timing will be equally bad.

I’m curious about this. Can you define bad step timing and good timing with some number? For example, if I run 250us base period with a 50us jitter, will that show up anywhere?
How tight does the timing need to be?