Quote:
Originally Posted by gnirts
After the fourth post, I really don't understand what's going on here.
Where can I find an introduction to whatever topic is being discussed, especially the last few posts by dcbrown and Dave K.?
Thanks in advance,
Robinson
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The origional post questioned how to do SPI (a synchronous Serial Periphial Interface) with the Robot controller. At the time I responded, I didn't notice that the origional post was a few months old, but the origional question really hadn't been fully explored, so I thought that I'd follow up with a quick example of how one can build interfaces like that with some relatively simple code, and provided some example code that I thought others might find useful.
dcbrown followed up with the correct observation that the RC (resistor capacitor) filtering on the user I/O lines limit the transition rates of the lines, and related personal experience in trying to interface a dual port RAM to the controller for the purpose of tying the RC to one or more other co-processing computers.
Aside from some follow up discussion on the timing considerations one needs to consider, and how to analyze them, I expanded on DC's train of thought in tying co-processing or other I/O devices to the RC and suggested that using an async serial port is much easier to debug.
"chips" with SPI interfaces on them will typically accept moderate to high clock speeds (100's of kHz to several MHz) and can be a very convienent way to expand the capabilitys of a small microcontroller, such as the one used in the IFI RC, without tying up a lot of the I/O pins on the processor itself.
The RC is flexible enough that if you don't consider both the software as well as hardware ramifications when choosing how to interface a more complex periphial to the controller, then you may be setting yourself up for more work than you bargained for... especially if you don't have the proper tools (which could be hardware, software, or a combination thereof) to debug the problem.
dcbrown rightly raised the real world impacts that the hardware RC filtering IFI added were relevant to the discussion and highlight the fact that the software folks need to understand enough about the hardware to take such factors into considersation... likewise, hardware designers need to understand enough about the ramifications of their descisions such that the software doesn't become impossible to impliment.
The bottom line is that interfacing devices with SPI interfaces to the RC is both possible and practical as long as you are careful to consider
all of the requirements.
If anyone is interested in more details related to interfacing an SPI device, we can go deeper into the details if you like.
I hope this helps...