RE: BeagleBone Control Stepper Motors with PRU - Part 2: Test Driving Outputs

Jan Cumps — Mon, 19 Aug 2019 11:39:51 GMT

Example C program that sends data to the PRU: https://git.ti.com/pru-software-support-package/pru-software-support-package/blobs/master/examples/am335x/PRU_ADC_onChip…

It uses the same mechanism as Linux command line, using the character device /dev/rpmsg_pru30.

RE: BeagleBone Control Stepper Motors with PRU - Part 2: Test Driving Outputs

Jan Cumps — Thu, 25 Jul 2019 08:15:04 GMT

Here's a first capture.

Command executed:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:3ef06e6b-9b7d-4651-b12d-db8be7f5e991:type=text&text=echo+%221150%22+%3E+%2Fdev%2Frpmsg_pru30]

First char is '1'. It tells the PRU to dive the DIR pin high.

The remainder is '150', telling the PRU to create a train of 150 pulses

The main ARM controller only spends time when submitting the command, almost nothing.

Even if you tell the PRU to generate a few thousand pulses, the time spent in Linux is a few miliseconds.

You can keep on submitting commands from Linux while the previous command is still executing. They are queued and the PRU picks them up 1 by 1.

[View:/resized-image/__size/634x380/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-dd8a6df0-c408-4d6d-8503-837415c0f495/2475.contentimage_5F00_204091.png:634:380]

I removed the wait time, so this is close to the maximum frequency I can achieve.

The code isn't optimised. I could eek out some clock ticks by easy optimisations - but at the cost of readability.

It's frequency is 6.7 MHz. I don't think optimisation is needed for a stepper motor.

Below capture is when I execute the command:

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:3ef06e6b-9b7d-4651-b12d-db8be7f5e991:type=text&text=echo+%2204%22+%3E+%2Fdev%2Frpmsg_pru30]

It drives DIR low and generates 4 pulses. Ideal to get a few pulses on the screen in good resolution.

I've added the frequency at the bottom of the screen.

[View:/resized-image/__size/620x372/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-dd8a6df0-c408-4d6d-8503-837415c0f495/1070.contentimage_5F00_204092.png:620:372]

RE: BeagleBone Control Stepper Motors with PRU - Part 2: Test Driving Outputs

Jan Cumps — Wed, 24 Jul 2019 21:49:00 GMT

Code Composer Studio project and build instructions attached.

RE: BeagleBone Control Stepper Motors with PRU - Part 2: Test Driving Outputs

DAB — Wed, 24 Jul 2019 21:03:06 GMT

Nice walk through of the Linux driver software.

DAB