BeagleBone Control Stepper Motors with PRU - Part 5: It Works

RE: BeagleBone Control Stepper Motors with PRU - Part 5: It Works

clem57 — Sat, 17 Aug 2019 13:27:30 GMT

I liked the tip about putting motor to sleep and avoid all the heat!

RE: BeagleBone Control Stepper Motors with PRU - Part 5: It Works

Jan Cumps — Sat, 17 Aug 2019 12:14:47 GMT

Here's a shell script that loads latest PRU firmware and sets all pins.

If you pass --test as parameter, it 'll move the motor 20 steps right and left

Assumptions: you followed the blog (specific: copied the binaries for SPI and PRU to the /home/debian/bin folder and loaded the SPI overlay).

Be sudo.

to configure the bb:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:3ef06e6b-9b7d-4651-b12d-db8be7f5e991:type=text&text=.%2FPRU_STEPPER.sh]

to also perform a test, then

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:3ef06e6b-9b7d-4651-b12d-db8be7f5e991:type=text&text=.%2FPRU_STEPPER.sh+--test]

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:3ef06e6b-9b7d-4651-b12d-db8be7f5e991:type=text&text=%23%21%2Fbin%2Fbash%0A%0APRU_STEPPER_link%3D%22%24%28readlink+-f+%2Fhome%2Fdebian%2Fbin%2Fbb_PRU_STEPPER.out%29%22%0Afw0_link%3D%24%7BPRU_STEPPER_link%7D%0A%0Aif+%5B+%24%7Bfw0_link%7D+%5D%3B%0Athen%0A+++++echo+%22stop+the+program+if+running%22%0A+++++echo+%27stop%27+%3E+%2Fsys%2Fclass%2Fremoteproc%2Fremoteproc1%2Fstate+2%3E%2Fdev%2Fnull%0A+++++rm+%2Flib%2Ffirmware%2Fam335x-pru0-fw+%26%3E+%2Fdev%2Fnull%0A%0A+++++ln+-s+%24%7Bfw0_link%7D+%2Flib%2Ffirmware%2Fam335x-pru0-fw%0A%0A+++++echo+%22load+the+firmware+to+PRU%22%0A+++++echo+%27am335x-pru0-fw%27+%3E+%2Fsys%2Fclass%2Fremoteproc%2Fremoteproc1%2Ffirmware%0A%0A+++++echo+%22start+the+program%22%0A+++++echo+%27start%27+%3E+%2Fsys%2Fclass%2Fremoteproc%2Fremoteproc1%2Fstate%0A%0A+++++echo+%22%22%0A+++++echo+%22Firmware+is+running%22%0A+++++echo+%22%22%0Aelse%0A+++++echo+%22Firmware+.out+files+does+not+seem+to+exist.+Did+you+place+%22+%24%7BPRU_STEPPER_link%7D+%22%3F%22%0A+++++echo+%22%22%0Afi%0A%0Aecho+%22sleep+on%22%0Aecho+out+%3E+%2Fsys%2Fclass%2Fgpio%2Fgpio30%2Fdirection%0Aecho+0+%3E+%2Fsys%2Fclass%2Fgpio%2Fgpio30%2Fvalue%0A++%0Aecho+%22reset+off%22%0Aecho+out+%3E+%2Fsys%2Fclass%2Fgpio%2Fgpio31%2Fdirection%0Aecho+0+%3E+%2Fsys%2Fclass%2Fgpio%2Fgpio31%2Fvalue%0A%0Aecho+%22set+pin+29+and+31+as+PRU+GPIO+out%22%0Aconfig-pin+P9_31+pruout++++%0Aconfig-pin+P9_29+pruout++++%0A%0Aecho+%22initialise+SPI%22%0A%2Fhome%2Fdebian%2Fbin%2Fbb_LINUX_STEPPER_SPI+%0A%0Aecho+%22stepper+motor+control+ready+from+PRU0%22%0A%0Awhile+test+%24%23+-gt+0%0Ado%0A+++++case+%22%241%22+in%0A++++++++--test%29+%0A+++++echo+%22test+requested%22%0A+++++echo+%22sleep+off%22++%0A+++++echo+1+%3E+%2Fsys%2Fclass%2Fgpio%2Fgpio30%2Fvalue%0A%0A+++++echo+%22motor+move+start%22%0A+++++echo+%27120%27+%3E+%2Fdev%2Frpmsg_pru30%0A+++++echo+%27020%27+%3E+%2Fdev%2Frpmsg_pru30%0A+++++sleep+1s%0A+++++echo+%22motor+move+stop%22%0A%0A+++++echo+%22sleep+on%22%0A+++++echo+0+%3E+%2Fsys%2Fclass%2Fgpio%2Fgpio30%2Fvalue++++++++%0A++++++++++++%3B%3B%0A++++esac%0A++++shift%0Adone]

For heat dissipation reasons, I turn the motor in sleep mode when the script exits.

To wake it up, execute:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:3ef06e6b-9b7d-4651-b12d-db8be7f5e991:type=text&text=echo+1+%3E+%2Fsys%2Fclass%2Fgpio%2Fgpio30%2Fvalue]

To make the motor take 20 steps, execute

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:3ef06e6b-9b7d-4651-b12d-db8be7f5e991:type=text&text=echo+%27020%27+%3E+%2Fdev%2Frpmsg_pru30]

To make it go back to sleep:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:3ef06e6b-9b7d-4651-b12d-db8be7f5e991:type=text&text=echo+0+%3E+%2Fsys%2Fclass%2Fgpio%2Fgpio30%2Fvalue]

I made this script to make development easier. I compile the binary in CCS then move it to the BB. A single command deploys and tests ...

RE: BeagleBone Control Stepper Motors with PRU - Part 5: It Works

Jan Cumps — Sun, 04 Aug 2019 13:29:42 GMT

The evaluation software for the DRV8711 stepper motor controller kit is very good.

[View:/resized-image/__size/611x447/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-c11b0eef-16fa-40ce-8a08-df8c13ff997f/4670.contentimage_5F00_204201.png:611:447]

You can use it to test the driver IC (you need a MSP-EXP430G2MSP-EXP430G2 LaunchPad but that one is cheap)

You can set motor control parameters. They are dependent on the (current of the) motor you have,

Several scenarios can be validated and played with.

This helps to better understand the datasheet.

It documents all the register settings and what they do. But getting smooth operation is not that easy by just staring at a PDF.

With the GUI, you can observe the motor behaviour, and then check what configuration settings were applied to the driver:

[View:/resized-image/__size/606x435/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-c11b0eef-16fa-40ce-8a08-df8c13ff997f/8865.contentimage_5F00_204202.png:606:435]

You can also evaluate the other way around. If you know the register values that a particular firmware uses, you can enter those values in the GUI.

The registers are broken up in their meaningful entities. There's support to show the raw HEX values.

You can change the registers in the GUI and write them to the driver IC. You can see the motor's behaviour under the circumstances directly.

This works more intuitive than changing the code and running the firmware again.

It also helps to find out what the maximum reliable speed is for your motor in a particular application and what an acceptable acceleration rate looks like.

I used this program in this blog series to set up a smooth full-step motor pattern and to see what frequencies and accelerations are OK for my motor.

It's part of the next step in the series, where I'll try to let the BB PRU calculate a nice smooth trapezoid velocity ramp.

[View:/resized-image/__size/596x408/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-c11b0eef-16fa-40ce-8a08-df8c13ff997f/4263.contentimage_5F00_204203.jpg:596:408]

Real good evaluation utilities can give a head start. This GUI has done that in the past when I developed for the programmable timer controller of a Hercules MCU.

I'm using (and appreciating) it again now for the BeagleBone's PRU programming.

RE: BeagleBone Control Stepper Motors with PRU - Part 5: It Works

DAB — Fri, 02 Aug 2019 20:52:53 GMT

Great finish Jan.

DAB