NXT programmable brick : 401


Robotics / NXT / 401	400 \| 402

Subject:	Re: What do these macros do?
Newsgroups:	lugnet.robotics.nxt, lugnet.robotics
Date:	Sun, 21 Jan 2007 10:11:19 GMT
Viewed:	13674 times

In lugnet.robotics.nxt, John Hansen wrote: > Unfortunately, there isn't really an easier way to clear the screen other than > to use some sort of system call which draws on the screen. That's because only > those system calls set the display as "dirty" and if that doesn't happen then > the firmware will not do the right thing when you draw directly to the screen > memory. There isn't any way to directly set the dirty flag because it is not > exposed via the IOMAP structure. > > John Hansen Thanks for your response, John. That tip about the dirty flag not being IOMAPpable is very, very useful; I could have wasted a lot of time working that out the hard way. I'm working on a graphical display widget to show a 'radar' (well, sonar) screen on a portion of the full screen. I was trying to figure out how to cleanly and quickly redraw the radar screen when new data became available. My experience with the IOMAP calls is that they're pretty slow - it must be doing some costly address lookup each time? Anyway, I'm leaning toward storing a <=800 byte copy of screen memory down in local memory, and just making one to eight syscalls to copy the relevant portions, rather than trying to write a smaller but significant number of individual bytes. I guess I should do some time trials to test this theory out :) Just received my rechargeable battery, colour sensor and compass. Time for mischief. Jeff Elliott

Message has 1 Reply:

		RE: What do these macros do? [IOMAP Access Execution Times
(...) You're right. IOMapRead and IOMapWrite are very slow functions. They're slow because you pass a character string for the name of the module you want to access; the NXT-G firmware runs through the list of modules looking for a match on the (...) (17 years ago, 21-Jan-07, to lugnet.robotics.nxt, lugnet.robotics)

Message is in Reply To:

		Re: What do these macros do?
(...) Lots of very cool stuff deleted. Sorry I missed your original message, Jeff. You can write to both the Normal and Popup screen memory and toggle back and forth between which one gets displayed. This code flips between the two buffers for 10 (...) (17 years ago, 16-Jan-07, to lugnet.robotics.nxt, lugnet.robotics)

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