lab 75 - scope & experiments


lab75 - scope & experiments


Since i did lab 67 i've been trying to improve/fix the t3 port and experiment with it. So this post has small report of the T3 port status, and some experiments under Inferno; note that they're not dependent of the handheld.


Some of the thing i've fixed are:

t3 touchscreen: Perform corrections to make it work as it should, this was important since it has direct impact on using Acme, and the rest of the system.

blank the lcd: Added code to turn off the lcd while playing music, so battery lasts longer. To do so i added an blank command to the devapm.c written by Alexander Syschev, and wrote a blight script that manages the lcd backlight,to control this from acme.

Since this changes apply to the t3 port, they can be found under lab 67 of the inferno-lab

While i haven't been able to fix the following segfaults, i've been able to obtain dumps and open them with gdb. So i've been able to find where the crashes happen, but still don't understand why they happen, so i'll have to read more.

* sys->print('%g', ...): with floating formats strings: "%g", "%f",when emu crashes it says

 "malloc failed at <addr>"
and if i disassemble emu, i can find that the <addr> corresponds to dopoolalloc(), and the core dump says that the crash happends at /libmath/dtoa.c:/rv_alloc\(i\)/ .

* emu -c1 /dis/sh.dis: emu starts loading Emuinit /appl/cmd/emuinit.b, it's able to load a few modules on which /dis/sh.dis depends (disdep /dis/sh.dis) but it crashes while loading Filepat, this seems harder since i'm still learning about arm architecture, and i know even less about jit.


Some of them were begun on lab 67 but i've improved them a bit and it's worth to dedicate them a new post.

scope.b: Parallel to the work of caerwyn with the DSP toolkit, i thought that it would be interesting to have a flexible oscilloscope, to view signals. So i started with the scope.b of lab 12, and started to add:
make it look nicer (add grid, and signal info)
make it more flexible, adding some options and widgets to control the oscilloscope. Also in this direction: allow resizal of the oscilloscope window.
and more
frequency spectrum of the signal (using fft).

And the result has been:

From inferno photos
If you want to play with it there's a guide file that i wrote while coding and can give some ideas about it's usage.

voip: this basically using stream to stream the recording of a microphone to the headphones of another computer, in short:
styxlisten tcp!firulillo!styx export '#A';
mount tcp!firulillo!styx /n/remote;
stream /dev/audio /n/remote/audio;
after some attemps i decided to pack it under a script that could be used both for publish '#A' (server) and to mount '#A' (client), the problem is that if you try, the sound appears delayed and some echo.

Reading stream(1) i noticed that stream ussies writes of bufsize (by default Sys->ATOMICIO: 8192), and to do it has to wait until it has bytes bufsize, so here was the reason for the delay and echo. Playing with bufsize, i set it by default to 1024 bytes, this works on a local net, probably it'll need adjustment for other situations.

player: i started this as a music player for the handheld, but i've ended using it under the PC, it's simply a script that lists the music files at cwd and plays them with a music player available in the host os: mplayer. A nice thing is that one can export a dir containing a collection of music files with:
 styxlisten -A 'tcp!*!styx' export /n/local/music
mount them from another machine under /n/remote and play them running:
 mount -A 'tcp!$server!styx' /n/remote
cd /n/remote && player

kbd2skini.b: This is just an idea in the direction of the DSP toolkit, currently the DSP toolkit is able to generate music, from standard music formats mainly contained in files (midi,skini).
I would like to play with the input devices available under inferno to use them as instruments. So i started to gather for similar things and found pc2midi (and some useful tutorials).

I've choosen the kdb as starting point, but it has it's limitations as it's discussed on the previous reference, since you don't have a pressure indication, instead the state of each key is either pressed / or not pressed, moreover there's no way to notice that there're multiple keys pressed at a time. We'll see what can be done with this, but could this be more than a joke?



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