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00:05 -!- Topic for #hplusroadmap: biohacking, nootropics, transhumanism, open hardware | this channel is LOGGED: http://gnusha.org/logs | https://diyhpl.us/wiki | not quite sponsored by george church | banned by the MIT media lab and the FDA
00:05 -!- Topic set by fenn [~fenn@user/fenn] [Fri Mar 25 06:29:19 2022]
00:05 [Users #hplusroadmap]
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00:05 -!- Channel #hplusroadmap created Wed May 19 06:51:36 2021
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01:45 < nmz787> muurkha: it doesn't *need* to be in a clean room... it's just the upgrade over "dexter" (the non-animated TV show) style plastic sheeting wrapped around a room
01:45 < nmz787> that I want
01:45 < nmz787> I had some concerns with particles for some things I've done in the past in just my garage
01:48 < muurkha> plastic sheeting wrapped around a room is a valid way to do a cleanroom
01:49 < nmz787> it just wasn't ideal
01:50 < nmz787> just got a micropython C extension compiled for the G491 that is just toggling a digital pin as fast as I could with a reasonably short for-loop... getting about 33 MHz, though the waveform isn't square
01:51 < nmz787> looks like I'll need a buffer on the DAC even if I use the OPAMP to buffer it
01:51 < nmz787> but the DAC and ADC work, I shorted them and wrote some code to shove out a sine wave
01:52 < nmz787> I have to figure out slaving the ADC and DAC off a common timer
01:53 < nmz787> I'm hoping this ADC+DMA triggered via a timer code I wrote years ago will help make that faster 
01:53 < nmz787> https://github.com/nmz787/culture_shock/blob/master/FOR_ADC_DMA__MP_1_9_4__adc.c.patch
01:54 < nmz787> also read about piezo electric response, hysteresis compensation (tldr; drive charge, not voltage... basically) 
01:55 < nmz787> started looking at the high-speed AFM imaging paper and thinking of what I need to code up, as well as studying their buffer circuit (and reasoning behind that, linked to piezo response, etc)
02:02 < nmz787> muurkha: do you have your devboard handy this week? to try replicating instructions I'm writing up? You could at least get to the python prompt and toggle the LED, in lieu of an oscilloscope, etc...
02:02  * nmz787 sleeps
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06:03 < superkuh> Weird enough to be worth sharing here: a parasitic vine that seems to mimic the leaves of nearby plants which also apparently does so for artificial/fake plants, suggesting a primitive form of plant vision?! https://www.tandfonline.com/doi/full/10.1080/15592324.2021.1977530 "Boquila trifoliolata mimics leaves of an artificial plastic host plant"
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07:24 < kanzure> what about the octopus camouflage stuff, has anyone tested whether it requires octopus eyesight?
07:26 < kanzure> "light-activated chromatophore expansion" https://journals.biologists.com/jeb/article/218/10/1513/759/Eye-independent-light-activated-chromatophore
08:16 < muurkha> nmz787: I still have to build a devboard for my STM32G491RET6 :(
08:16 < nmz787> oh, you didn't buy the nucleo board :(
08:18 < muurkha> "drive charge, not voltage" sounds interesting!  how do you do that in practice?  charge up a high-voltage C0G/NP0 cap to precisely measured voltages and dump them onto the piezo?
08:23 < nmz787> the stuff I saw was all active using integrators on the output, basically... but then you get things like drift that you have to compensate for (cue the last 20-40 years of academic references)
08:23 < nmz787> the last one I read used "DSP" instead of hardware compensation
08:23 < muurkha> integrators made out of an op-amp, a capacitor, and a resistor?
08:23 < nmz787> yeah something like that
08:25 < nmz787> maybe a .wik Varicap
08:25 < nmz787> .wik Varicap
08:25 < saxo> "In electronics, a varicap diode, varactor diode, variable capacitance diode, variable reactance diode or tuning diode is a type of diode designed to exploit the voltage-dependent capacitance of a reverse-biased p–n junction. /  Varactors are used as voltage-controlled [...]" - https://en.wikipedia.org/wiki/Varicap
08:27 < muurkha> how would a varactor help?  I'd think that in an integrator like that any variability in capacitance would be a source of error to eliminate, not something desirable
08:27 < nmz787> yeah idk, just came to my mind as "how would I integrate"
08:28 < muurkha> also I think that in practice you'll have to connect the integrator to an amplifier because you can't put as much charge on a precision cap as you can on a piezo (the precision cap would have to be 100× as physically big as the piezo) and that's another source of drift
08:28 < nmz787> as long as the capacitance has some means to be set on a stable value....
08:28 < muurkha> maybe it would be best to servo the position of the piezo instead of its charge or voltage
08:28 < nmz787> I didn't come up with a good capacitance/charge value needed to sweep against
08:29 < nmz787> doesn't "servo" just mean add some sensor to measure movement?
08:29 < muurkha> by "servo" I mean "use closed-loop feedback to control"
08:30 < muurkha> commonly the thing you're controlling is position or speed, but you can think of an op-amp as "servoing" a voltage or current
08:31 < muurkha> (in every use of an op-amp except as a slow comparator)
08:33 < nmz787> I was also looking for things like "driving piezo with sine wave hysteresis elimination"... i.e. maybe simply switching away from triangle waves would help 
08:34 < nmz787> then you might be able to  push the "linearization" to your ADC sample timing
08:37 < muurkha> yeah, to the extent that you can do your signal processing in the digital domain, you don't have to worry about linearity
08:38 < nmz787> (sine wave movement is how the high-speed corneocyte AFM paper implemented things... though they may not have been as concerned with linearity of their image) 
08:38 < muurkha> also, to the extent that you can adjust things in the time domain rather than the voltage domain, you will get a lot of improvement in precision
08:39 < muurkha> just because even the cheapest quartz crystals have about an order of magnitude lower error than bandgap voltage references, and you can push them to two orders of magnitude better
08:40 < muurkha> (that means using PWM instead of a DAC)
08:40 < muurkha> (or uh PDM)
08:40 < nmz787> .wik PDM
08:40 < saxo> "[Disambiguation] Personal data manager - portable hardware tool enabling secure storage and easy access to user data Phase dispersion minimization, a data analysis technique for finding periodic components in time series data Physical data model, a representation of a data [...]" - https://en.wikipedia.org/wiki/PDM
08:41 < nmz787> pulse density modulation?
08:41 < nmz787> isn't that basically PCM audio??
08:41 < nmz787> .wik pulse density modulation
08:41 < saxo> "Pulse-density modulation, or PDM, is a form of modulation used to represent an analog signal with a binary signal.  In a PDM signal, specific amplitude values are not encoded into codewords of pulses of different weight as they would be in pulse-code modulation (PCM); [...]" - https://en.wikipedia.org/wiki/Pulse_density_modulation
08:41 < muurkha> no, it's basically sigma-delta audio
08:42 < muurkha> like SACD.  PCM is like CD-DA
08:43 < nmz787> hmm, I will look for PWM/PDM AFM references later
08:43 < nmz787> that should be easy for the MCU
08:43 < muurkha> you might be able to spew out a PDM bitstream on one of the SPI interfaces
08:43 < nmz787> this G491 even has a high-res timer, which might be useful
08:44 < muurkha> yeah, that high-res timer is insane, isn't it?  have you tested it?
08:44 < nmz787> nah, I haven't even looked at the specs
08:44 < nmz787> saw someone who had some examplke code for it tho
08:45 < nmz787> I think you'd just pre-compute a lookup table of values to be streamed out, and tell the timer/DMA/DAC to use that block for new "codes" to shove out
08:47 < muurkha> for SPI PDM you mean?  not for the timer
08:55 < nmz787> for both
08:56 < nmz787> the timers are quite powerful IP blocks on these STM32s
08:56 < nmz787> I guess they have a lot of stuff for variable PWM sort of applications
08:57 < nmz787> like, one timer periodically loads another timer's compare register, using DMA from a buffer/LUT, to change the pulse width 
08:58 < nmz787> a lot of options to connect/trigger/influence one IP block to another
09:01 < muurkha> I thought you were talking about the subnanosecond high-res timer designed for LIDAR
09:03 < muurkha> but the potential benefit of PDM is that, supposing you stay between ⅓ and ⅔ duty cycle, almost all the signal's energy is above fₛ/3
09:03 < muurkha> whereas for PWM typically we're talking about fₛ/256 or something
09:05 < muurkha> if you are worried about switching losses then PWM is a lot better because it has (in this configuration) about 100× lower switching losses
09:05 < nmz787> HRTIM, whatever that's for
09:05 < muurkha> how fast is HRTIM?
09:05 < nmz787> no idea
09:05 < nmz787> have only seen the register and some example code using it
09:06 < muurkha> I think that might be the insane one I was thinking of
09:08 < muurkha> but if you are trying for DAC that is as precise as you can make it, well, pushing the square-wave edges two orders of magnitude higher in frequency makes them easier to filter out in the analog domain
09:09 < nmz787> well there was something about driving the DAC with a sine wave, so you eliminate frequency domain noise in terms of the movement/dampening/settling of the tip location
09:10 < nmz787> and that allowing you to image faster, at the resonance freq of the cantilever
09:10 < nmz787> unless I'm misunderstanding the "square edge" reference
09:10 < nmz787> you talking about PDM still?
09:12 < nmz787> err, maybe I mean the "scanning tube" not cantilever
09:12 < nmz787> that's another thing I need to figure out, heh
09:12 < nmz787> getting tripods for cell phones tomorrow, so I plan to spend some time this weekend on asembling the AFM kit as delivered
09:13 < muurkha> PDM and PWM both, yeah
09:44 < nmz787> https://iopscience.iop.org/article/10.1088/0957-0233/17/9/003
09:44 < nmz787> .title
09:44 < saxo> ShieldSquare Captcha
09:44 < nmz787> A driving method of piezoelectric actuator by using current pulses
09:45 < nmz787> In this paper, a driving method with the intention of applying pulse density modulation control is proposed and the results of the displacement control of a stacked piezoelectric actuator are described. In the feed-forward control, the hysteresis and nonlinearity in the drive by the current pulse were much smaller than those by a voltage linear amplifier because the driving pulse with a constant 
09:45 < nmz787> duration can be regarded as a charge pulse.
09:46 < nmz787> gotta change to personal machine so I can scihub that
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12:02 < kanzure> .tw https://twitter.com/davidrliu/status/1590786935290617856
12:02 < saxo> As several commenters requested, here is a link to the seminar on base editing and prime editing that I recently gave at @broadinstitute and @ChemistryMIT. Thank you for hosting, Matt Shoulders, @ChoudharyLab, and colleagues! https://www.youtube.com/watch?v=6tHs6_l2hSY https://twitter.com/davidrliu/status/1584328902973206530 (@davidrliu)
12:02 < Muaddib> [6tHs6_l2hSY] Base Editing and Prime Editing: Precise Chemistry on the Genome without Double-Strand DNA Breaks (69:47)
12:10 < kanzure> .tw https://twitter.com/zhaoweiasu/status/1590437799995772928
12:10 < saxo> 4. It is well known that Prime Editing has achieved high efficiency, high specificity, and programmable gene CORRECTION. Meanwhile, Tessera’s Gene Writing technology may still struggle to achieve high efficiency, high specificity, and programmable gene INSERTION. (@zhaoweiasu, in reply to tw:1590437758790938624)
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15:46 < kanzure> https://www.hedweb.com/ "The Hedonistic Imperative outlines how genetic engineering and nanotechnology will abolish suffering in all sentient life."
15:46 < kanzure> apparently there is an EA subfaction splinter group that believes the optimal way to eliminate animal suffering is to kill all the animals, which is certainly another way of doing it!
15:49 < TMA> isn't that the basic tenet of the PETA?
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16:14 < fenn_> please name and shame the alleged splinter group
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16:21 < muurkha> kanzure: clearly negative utilitarianism leads almost immediately to the benevolent world-exploder
16:22 < kanzure> i don't actually know how to eliminate suffering in wild animals using genetic engineering; wouldn't it require being able to assess animal pain which is notoriously hard anyway?
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19:51 < jrayhawk> harm-minimizers always wind up anti-biotist
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21:37 < fenn> .tw 1589094830365630464
21:37 < saxo> We should put reactors on our cruise ships so we can make them even bigger. On-board downhill skiing. Skyscrapers connected with ziplines so you can play Spiderman. I want billions of people entering the global middle class and I want them to all get whatever fun shit they want. (@KelseyTuoc)
21:46 < Malvolio> (animals suffer life is what happens)
21:47 < Malvolio> animals live to suffer why else would they do it so much!
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--- Log closed Fri Nov 11 00:00:13 2022