k0ngo

There's also a version with a built-in class D amplifier and color display. On the software side it's neatly packaged with a web UI for configuration, as well as support for snapcast (multiroom), airplay and pulseaudio besides spotify.

I'm not affiliated with them, just very tempted to build one.

Comment · 8 years ago

I'm a big fan of Fabrice Bellard, but there are other eNB and UE implementations that are fully open source, like OpenAirInterface[1] and srsLTE[2]

[1] http://www.openairinterface.org

[2] https://github.com/srsLTE/srsLTE

Comment · 8 years ago

The article doesn't mention it, but I think Fabrice Bellards PoC [1], in which he generated a valid DVB-T and PAL/SECAM carriers using a graphics card (2005), is very elegant and highly related prior art.

[1] https://bellard.org/dvbt/

Comment · 9 years ago

I'd expect scp to detect (using argv[0]) that it is called through a symlink and behave as rcp, not scp. This is how busybox is implemented, with many programs in one binary.

Comment · 9 years ago

I like the idea, but unfortunately PCIe isn't easy or cheap to implement on silicon. The problem is that you'd need the PHY, which is the high speed, analog interface, and that needs to be designed and tuned for the fab and process node you're targeting. In practice the only sane way to get PCIe on your chip is to buy a PCIe IP block from Faraday or Synopsys. The same goes for SATA. Ethernet and USB on the other hand is available in discrete PHY chips, so writing some open-source controller RTL for RGMII and ULPI is much more reasonable for an open-source chip. (Obviously, if someone would cough up the money for taping out a RISC-V SoC with PCIe PHYs onboard and make it in a large enough volume that the price gets down to reasonable levels, I'd be buying a bunch of'em.)

Comment · 10 years ago

Just as a software compilation flow is devided into preprocessing, compilation, assembly, and linking, a HDL flow is divided into synthesis, mapping, place and route, timing analysis and bitstream generation. RTL is the output of the synthesis stage and is readily available to the designer, typically both as code and as a graphical schematic.

Comment · 10 years ago

> On a different note, why is that (as far as non-expert me knows) that nice mics often have eq settings? Is this not a blatant layer violation?

The low-frequency/subsonic content that this switch will remove often consists of wind noise, pops from talking too close, vibrations from the floor/mic stand, etc. Even if these low frequency noises may be more or less inaudible, they'll contribute to a large signal swing that will decrease the headroom in the following amplifiers. In other words, you won't be able to turn up the gain in the microphone amplifier/mixer as much as you'd want, because the low-frequency but high-amplitude content will make the amplifier clip and distort the sound. Filtering the signal after the mic preamp won't solve the problem, because the preamp (which can provide in the order of 60 dB gain) will be the component that clips. By including a low-cut filter in the head amplifier circuit inside the microphone (the amplifier serves only as a buffer, and usually with unity gain), the disturbing low-frequency noises can be removed before entering the high-gain microphone preamp. You can find the low-cut switch next to the capsule in the U87 schematic [0]. It seems to me that they increase the capsule bias voltage, thus changing the low frequency response by electrostatically tensioning the membrane.

[0] http://recordinghacks.com/images/mic_extras/neumann/U87-sche...

edit: tweaked some things. meta: i'm not very good at commit messages.

Comment · 10 years ago

This. It is also important to note that you may interrupt the service of other people's handsets even if your BTS doesn't allow them to connect, just by operating your SDR with an insufficient clock reference [1]. The handset will re-calibrate it's VCXO to match your SDR, and then won't be able to see the legitimate cell networks.

[1] http://openbts.org/w/index.php?title=Clocks

Comment · 12 years ago

Yes, Point will perform all processing in the device and only send events with time stamps, as well as plain sensor readings for temperature/humidity/etc. It should be easy to verify by looking at the outbound bandwidth. Limiting outbound connections w.r.t hosts, ports and bandwidth (even filtering out OTA firmware updates) should be possible (as we're not trying to hide what we do, only protect your data), but it might affect the performance and battery life of the device, and is not something we can endorse.

Comment · 12 years ago

If the power goes out or the router gets funky, most internet connected solutions would go offline anyway. But, being battery powered, Point would at least still be active and keep track of things. The fact that the device has lost it's connection to the cloud will trigger a notification to the owner as well. The wireless configuration is done using an app and should be straight forward for most users. As long as the router is securely configured and the user is capable to connect a phone or laptop, installing Point should be piece of cake. As for being self-contained, we mean that it is plug-and-forget, without any cables or base stations. There might be methods of expanding the set of sensors, although at the moment, you see what you get. Adding a cellular modem to the device would make it deviate too much from our current concept in terms of cost (both manufacturing and recurring costs for the cell network usage) and power consumption, but it is something we might include in a future, special version for places without a permanent internet connection, like a cabin or boat.