User talk:Arjs

re: mediawiki script

Thanks for the reminder! Turns out that you need not just admin accounts on the wiki but access to the webserver, so I passed it on to SJ; when I see him in the office tomorrow afternoon I'll try to catch him to sit down and actually work through it (if it hasn't already been installed by then). In the meantime, try linking to the youtube video... Mchua 01:00, 22 July 2007 (EDT)

It works now; good luck. Sj talk 21:05, 22 July 2007 (EDT)

measure jam

Emailed the olpc.tv folks about the youtube-on-mediawiki coolness, thanks for the suggest! Also passed on the Measure project ideas to my classmates who were looking for projects; hopefully some of them will ping you soon.

The Jams page has a short paragraph describing Jams that you can use to send out to your classmates and friends in new Delhi - you can hook up with any of the existing/upcoming Jams or plan your own. I'm filling in the How To Run A Jam book as the Curriculum Jam Taipei gets underway, so hopefully that might be useful to you soon... and I think the idea of running an engineering Jam around Measure is awesome, you should go for it! (actually, it might work well if the leaders of one of the IEEE student chapters organized the Jam, and you were the resident OLPC/XO/Measure expert on hand.) Keep me posted, Mchua 21:31, 23 July 2007 (EDT)

Sweet, Measure Jam! Are you thinking of doing a tech-flavored Jam (develop software/periphs for Measure) or a more education-ish Jam (here, teachers, take stuff we've made and teach things with it)? There's also the option to do both; see Journalism Jam New York for an example of a Jam that combines toolmaking with tooltesting. 65.78.19.90 21:32, 13 August 2007 (EDT)

the pictures on your userpage

...are absolutely wonderful. Thanks for sharing them! You should email Walter so he can mention them in the weekly update. :) Mchua 18:22, 15 August 2007 (EDT)

Re: Picture positioning trouble

Hi could You show me an example of what your tying to do? --Chief Mike 09:36, 17 September 2007 (EDT)

picture tutorial

how's this? Mchua 13:15, 17 September 2007 (EDT)

RE: Status of Measure in OBX template

follow-up to User talk:Xavi#Status of Measure in OBX template

Oops! yes you're right. And yes, 'bundled' seems fine. The categorization is still not totally defined (that's why they are red/missing), so any suggestions & feedback are more than welcome.

I haven't removed the old {{Status box}} as I want to make sure there are no objections, and that the OBXes are helpful. Comments? :) --Xavi 11:20, 22 September 2007 (EDT)

I love the OBXes! They concisely convey all the most important things a new user might want to know about any activity. Although, I cannot think of any now, I would let you know of any suggestions for additional fields in the OBXes. Great work on the OBXes! --Arjs 11:53, 22 September 2007 (EDT)

USB measuring sensors for the XO

We are working on the USB measuring sensors for the XO. Here are some technical details. We can make the hardware work but we need an application for the XO that will allow kids to work with the sensors. If you are interested we can work together. ZdenekBroz 16:18, 14 October 2007 (EDT)

I would be glad to collaborate. I am a little hard pressed for time these days, so might not be able to undertake a lot of code-development work (I also have to complete feature requests and bug fixes within Measure ACtivity), however I would be happy to answer any of your questions and help you use or develop Measure Activity to suit your purpose. --Arjs 16:23, 14 October 2007 (EDT)

Feel free to email me at arjun at laptop dot org

polyphase filtering

Hope this helps. I checked the algorithm on paper (the math works out) and ran through a couple of test cases where it seemed to produce the correct output, but you may want to compare it to your current code and see if you get (1) the same answers, and (2) any performance gains. But in any case, I tried to comment the code enough that it's easy to follow the algorithm - polyphase filtering is really just doing (and adding) only the convolutions you won't be downsampling out. Mchua 01:21, 28 October 2007 (EDT)

def polyphase(signal, filt, samplerate):
        """Takes in a signal and a filter to convolve and a rate to sample at. Implements a polyphase filter that returns a downsampled version of the convolution."""

	# load convolve function
	from Numeric import convolve

	# Pad signal with zeroes so it's a multiple of samplerate
	# When the signal is split into polysignals, this should
	# pad the last N signals with zeroes at the beginning
	# (where N is -len(filt)%samplerate)
	# so that all polysignals are the same length
	signalpad = (-len(signal)%samplerate)
	signal = signal[:signalpad] + [0]*signalpad + signal[signalpad:]

	# Pad filter with zeroes so it's a multiple of samplerate
	# unlike the signals, the filters that need to be padded
	# should be padded at the end
	filt += [0]*(-len(filt)%samplerate)

        # Split original signal into polyphase signals.
	polysignals = []
	polysignals += [signal[offset::samplerate] for offset in range(samplerate)]
##	print "Polysignals", polysignals # debug

        # Split original filter into polyphase filters
	polyfilters = []
	polyfilters += [filt[offset::samplerate] for offset in range(samplerate)]
##	print "Polyfilters", polyfilters # debug

        # Filter each polyphase signal by corresponding polyphase filter
        # Add the results together
	ans = convolve(polysignals[0],polyfilters[0])
##	print "Ans:", ans # debug
	for count in range(1,samplerate):
		ans += convolve(polysignals[count],polyfilters[count])
##		print count, "Ans:", ans # debug
		
        # Done
	return ans

if __name__ == "__main__":
	from Numeric import convolve
	signal = range(2,16)
	filt = range(7)
	samplerate = 4
	print "The signal", signal
	print "Filtered with", filt
	print "And sampled at a rate of", samplerate
	print "Yields:", polyphase(signal, filt, samplerate)

Reverting a page to an earlier version

I saw your question elsewhere on the wiki; if you haven't already figured it out, here is a page describing how to revert a MediaWiki page to an earlier version. —Joe 13:35, 31 October 2007 (EDT)

image sharing

Images and files can't be shared across wikis in a simple way. You can link directly to images on the public site from the teamwiki page, though. Sj talk 09:19, 2 November 2007 (EDT)

volunteers for your projects

Back from three months of roaming the world and getting geared up on OLPC stuff again. Sounds like you've been busy! Some stuff you might want to know:

• Re: Help needed wrangling young testers at OLPC office - forwarded to the Olin university chapter folks, might be able to get some to help when they're back from winter break (January 20-something).
• Measure: The IMSA chapter, which you've already seen (and messaged User:ScottSwanson about, is making...
  • sensor input modules (starting with an adapted version of the differential amplifier and going forward; they're learning electronics as they do this so progress may be a little slow at first.
  • a collection of experiment demos (with videos) using Measure, among other Activities, so students and teachers have a few examples of the kinds of things they can try out.
  • More might be coming once the sensor input modules work. There was interest in continuing work on Measure-related things as a full-time research project over the summer, if we can wrangle some engineers to mentor via email. Let Scott know if you run across anyone; we'll keep our eyes open as well.
• Power supplies: Apparently one of the top engineers at Fermilab is very interested in OLPC, IMSA, and sustainable energy. He and one of the IMSA parents are building a small sustainable energy lab on campus (solar panels, wind power, and other common variants) and wants to donate to form an OLPC lab as well. So there's a chance we may be able to get some collaboration on alternative power sources. We're getting in touch with him (will mention Cow power) and will let you know if anything happens.

See you soon in Boston, I hope - will you be around for part of this winter?

Mchua 10:17, 11 January 2008 (EST)