I would never have guessed this configuration was so rare. D-sub connectors seem to have more active use in aerospace and defense that you might expect (Until I started working professionally, I always associated them with "old" computers, not high end stuff).
The important distinction is between on-silicon interconnects and off-silicon. On silicon, the interconnect density is much higher so it's feasible to get high bandwidth by having lots of "channels" (wide busses). This becomes less desirable off chip (on the PCB) for many reasons. Some of them are:
1) The interconnect density is much lower, and having such a large bus becomes physically large
2) The bus is larger and less precise, which makes maintaining skew between channels more and more challenging
3) The parasitic capacitance/inductance (i.e. energy storage) of the bus becomes larger as it gets physically larger, meaning each channel needs a relatively large driver circuit (which costs expensive silicon area) and dissipates more power to drive correctly, and even more power if the speed is increased.
Increasing the symbol complexity of each channel does more than just move the bottleneck around, because it allows fewer chip to chip interconnects to carry more data.
I don't work in this regime, but as a layman I'm not convinced using full QAM for on-board chip to chip interconnects makes sense. One major advantage you natively have over the RF case is you can be easily coherent (shared clock). Throwing this away to do carrier recovery introduces a lot of complexity and potentially reduces the available bandwidth. Assuming you transmit without a carrier, can you have "baseband" QAM without a separate I and a Q signal? If you transmit an I and Q signal separately, does that not just become the same thing as two PAM-32 signals?
There are a few drawbacks with transmitting QAM with two signals
- one needs 2 signals instead of one (2x total bandwidth)
- requires each channel bandwidth to extend to to DC, which had many other challenges
If one modulates the signal to shift it away from DC, the “negative/mirror” frequencies also shift, which means now bandwidth has doubled.
A QAM signal still has double the bandwidth of an equivalent PAM one but pays for it by encoding two PAM signals.
Of course, Discrete Multitone Modulation puts QAM to shame for non-flat channels as it can adapt near-perfectly to such. Not likely to happen for high speed interconnects in our lifetime. I suspect photonics will happen first.
It's up to hobbyists what's worth it to them, but the power consumption of the ESP 8266/32 is not _really_ comparable to the '430. "Deep sleep" mode on the ESP seems to be about 20uA, an MSP430FR5969 can go to a 20nA LPM 4.5 mode (factor of 1000 lower). Harder to compare in a HN comment, but active mode power consumption is also in the MSP's favor for many applications particularly when using the built in hardware accelerators like LEA.
Of course the MSP430 doesn't have a WiFi modem or a giant hobbyist community like the ESP, so I'm really not trying to make an argument for which is "better" just trying to add some contrast to the low power features you asked about.
I think the platform is very much still alive and kicking. It is still the only uP platform I am aware of which is available with embedded FRAM which is low power, non volatile, extremely more write durable than flash and rad hard. Again, maybe not top selling features for a hobbyist project but absolutely compelling for certain industrial use cases.
Thanks - you got me excited about MSP430 again. I am wondering if I should build an AC motor controller for fun, since I happen to have an AC motor on my bench.
No problem! You are not the first person I've heard express the impression that the MSP430 is slipping into irrelevance, and while I agree the places it shines may be getting squeezed by low power ARM parts I think they can be pretty compelling for applications where they are a good fit. They are simple, yet modern enough to support full featured c compilers, have a history of focusing on low power and the FRAM is a pretty solid differentiator if your use case can take advantage of it. Jay's article here can't really show any of that off because the one dollar price point is below the sweet spot where most of the nice features kick in
Don't know if their copy editors read these, but "Gallium Nitrate" is surely a typo for "Gallium Nitride" (GaN). GaN is a wide bandgap semiconductor, Gallium Nitrate is apparently some sort of drug.
It's because the speed of sound (in any material) is much slower than the speed of light (even in high dk materials). To make a selective and low loss filter you want to use resonators which have dimensions which are a large fraction of a wavelength (i.e. a quarter wave). When the wave speed is slower, a wavelength is compressed into less space ( cycles per second / meters per second ) which is what enables the miniaturization.
I believe the acoustic loss in many of these materials is also lower than the dielectric loss in most materials, which also improves filter q and achievable selectivity.
Just a hint - extra attributes in the `mkShell` appear as environment variables in the built shell. So instead of a `shellHook` for this you can just have an attribute `ERL_LIBS="";`
I'm not completely sure but I think this approach is preferred because shellHook only runs in `nix-shell` but if you ever wanted to `nix-build` a release it might not run.
There tools like direnv, that "enter" your env environment as soon as you cd to the directory. This is implemented by changing environment variables like PATH.
Because shellHook allows on executing any code, there's no standardized way to undo what it executes, so those tools don't execute that part.
Down to DC? That should be a surprise, because it's certainly not true! Faraday's law of induction only applies to varying fields, which means AC or physical movement. Remember, it's perfectly normal and common to have a square wave with a DC component of zero!
Yeah, they’re almost definitely referring to the control signal. Since it’s controlling the saturation of the core, it’ll happily go down to DC just fine.
