[Oberon] Interfacing with Foreign Systems

Skulski, Wojciech skulski at pas.rochester.edu
Fri May 1 21:18:41 CEST 2020

Liam wrote

> ARM is a fairly clean instruction set. The Rasπ design is quite simple. 

I am more familiar with BeagleBone Black which is the same idea as RPi. It was built around ARM AM3358, which is a single core ARM of roughly similar complexity to other ARM systems-on-chip. I believe that lessons from BBB are about the same as the lessons from RPi. So here is the first lesson. Go to the Texas instruments web site and download the AM355x Technical Reference Manual, Literature Number: SPRUH73Q, dated October 2011–Revised December 2019. Open that file and look at the page counter. I am seeing 5118 pages. Please spend some time reading that manual, putting yourself in the shoes of an educator who will be explaining these concepts to students. Please try explaining the GPMC, the PRU-ICSS, McASP, or EDMA. How are these pieces connected and what are they doing? (I am intentionally not deciphering these acronyms. Simple is simple, right?)  After spending a couple hours preparing an imagined course please come back and explain the meaning of the word "simple". 

Perhaps what you meant was "board design was simple". I submit to your consideration that a computer science educator is not supposed to focus on the board design. Routing the wires and soldering the chips are not at the bottom of computer science. The system architecture is the focus. The architecture is hidden inside the chip and explained on five thousand pages. So now try making it the basis of the education.

You might say that this is not fair because we should be talking of RPi. But RPi design is closed, like Paul just said. So we cannot even open the manual. How can you use something for education which is probably even more complex (a multicore chip!) and the details were hidden?

Using RPi for education is cheating in my humble opinion. They take a horrendously complex system, hide most details, make it a black box to students and most educators, and run Python on it. This is not computer science. This is Python science. Cheap science, in my opinion. It is educating students how to implement standard exercises in standard ways. It is not teaching creativity. It is teaching how to follow the crowd. (Again my opinions.)

> And it's £25 and there are literally millions of them out there.

The economy of the mass production should not be misconstrued for intellectual merit.

Paul said: 
> BTW I do think it's a scandal (but not surprising) that parts of a
> computer targeted at education are under NDA.  But much has been written
> elsewhere about that.  Then again, I don't think even the Micro:bit is
> completely open.  And even that is waaay more complicated than our RISC
> computer, though less powerful.


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