Signal& Bus Segments

  • Signals are a limited form of inter-process communication (IPC), typically used in Unix, Unix-like, and other POSIX-compliant operating systems.A signal is an asynchronous notification sent to a process or to a specific thread within the same process to notify it of an event. Signals originated in 1970s Bell Labs Unix and were later specified in the POSIX standard.
  • In signal processing, a signal is a function that conveys information about a phenomenon. In electronics and telecommunications, it refers to any time varying voltage, current or electromagnetic wave that carries information. A signal may also be defined as an observable change in a quality such as quantity.

A signal is generated by some abnormal event, initiated either by user at a typewriter (quit, interrupt), by a pro- gram error (bus error, etc.), or by request of another pro- gram (kill). Normally all signals cause termination of the.

Existing Signal users might be getting more notifications than usual. “Jack is on Signal,” “Cathy is on Signal,” “Miriam is on Signal,” all pings showing phone contacts who are joining the secure messaging app.

Those pings reflect the fact that there’s been an influx of new users. Known for its end-to-end encryption and independent structure as a non-profit organization run by a foundation — not a big tech company — Signal has previously been the communication method of choice for activists, people in the hacker community, and others concerned about privacy.

Recently, it’s gone mainstream.

Recently, Facebook-owned WhatsApp — which is end-to-end encrypted using Signal’s protocols — began issuing a privacy update notification to users making clear that it is sharing user data with Facebook (which it has actually been doing for years). That’s led people to look elsewhere for a secure communications app, helped along by Elon Musk’s Jan. 7 tweet which simply stated: “Use Signal.”

Signal Messenger

Over the past three years, Signal has also been investing in more infrastructure and features to support its users. That's a good thing: Signal first saw an increase in users in the spring as people participating in anti-racist protests around the killing of George Floyd realized how closely law enforcement was surveilling them and asking companies to hand over user data. It’s only become more popular since then. As of this writing, Signal is at the top of the Apple App Store and Google Play Store, and its two-factor authentication onboarding system even got briefly delayed Thursday because so many people were trying to sign up.

So, thinking about joining Signal? Bottom line: If you care about privacy, it’s a good idea. Here’s what you need to know.

OK, so what is Signal?

Signal is a free, privacy-focused messaging and voice talk app you can use on Apple and Android smartphones and via desktop. All you need is a phone number to join. You can text or make voice or video calls with friends, either one-on-one or in groups, and use emoji reactions or stickers just like in other apps. But there’s one big difference: Signal is actually really private.

Is the Signal app secure?

Communications on Signal are end-to-end encrypted, which means only the people in messages can see the content of those messages — not even the company itself. Even sticker packs get their own special encryption.

Signal created the encryption protocol (basically, the technical way you implement this) that other companies including WhatsApp and Skype use. Plainly put, it is the gold standard of privacy.

Is Signal really private?

Yes — and that privacy goes beyond the fact that the content of your messages is encrypted. You can set messages to disappear after certain customizable time frames. Plus, Signal collects virtually no data on its users. The only information you give the app is your phone number, and the company is even working on a way to decouple that from using Signal by making encrypted contact servers. If the police come knocking to Signal for data on its users, it says, truthfully, that it has no data to hand over.

There are no 'safe' jurisdictions anymore, only safe services. This is the entirety of what the DOJ's jurisdiction got them: pic.twitter.com/xnQ5tW58FD

— Signal (@signalapp) October 4, 2016

Part of the reason it collects no data is because Signal is a non-profit organization, not a for-profit company. It has no advertising, so no incentive to track users. Instead, it’s funded by grants and private investors — one of whom had a huge personal interest in making a privacy-oriented platform. Though a small group of privacy activists created Signal in 2013, it has grown in recent years. In 2018, WhatsApp founder Brian Acton donated $50 million to create the Signal Foundation, which now runs Signal. Acton got on board with the mission to make a truly private messaging service after Facebook acquired WhatsApp and Acton reportedly left the company amid clashes with Facebook over how it was eroding WhatsApp’s privacy.

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Signal vs. WhatsApp (and other messaging apps).

Both Signal and WhatsApp are end-to-end encrypted using the same technology. That means the content of the messages you send and calls you have are both private. However, Facebook collects lots of other information in the form of usage statistics, metadata, and more. And there’s no longer a way to opt out.

You can make an app used by many millions of people that has no data..Cool chart by @forbes & @UKZak 🙈🙊🙉 https://t.co/gWFqyIeoZ3pic.twitter.com/Unngddaq5M

— Signal (@signalapp) January 5, 2021

Signal does not have as many fancy customization features as WhatsApp, like backgrounds. But when it comes to true privacy, there is no comparison.

Signal Download

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You can see a full list of alternatives to Facebook-owned messaging services here.

Another app rising in popularity is Telegram. Telegram says it’s also all about privacy, but it actually has plenty of downsides. Messages on Telegram are not truly end-to-end encrypted by default. Plus, the fact that private groups are unlimited in size, can be joined via a link, and are explicitly not moderated has made it a hotbed for toxic and illegal content, like terrorism and revenge porn (also known as non-consensual pornography). Signal does not moderate content either, but it limits groups to 1,000, and is more about communicating with people who are actual contacts than joining groups of strangers like on WhatsApp and Telegram.

Where to download Signal

You can find Signal in Apple’s App Store or in the Google Play store. It’s currently very easy to find since it’s sitting right at the top of the Free Apps chart.

WATCH: How to permanently delete your social media

Introduction

Controller area network (CAN) offers robust communication between multiple network locations, supporting a variety of data rates and distances. Featuring>MCP2515: #TQ for 1-Mbps Operation fOSCBRP = 1BRP = 2BRP = 3BRP = 44020106.667538199.56.333
4.7530157.5
53.75201053.3332.51052.51.6671.25
ADSP-BF548: #TQ for 1-Mbps Operation
fSCLKBRP = 5BRP = 6BRP = 7BRP = 8
13326.622.167
1916.625
1002016.66714.28612.5
50108.33337.1436.25
40 86.667
5.714
5

Step 2: Determine Bit Segment Configuration

The next step is to determine the number of TQ required for each bit segment. The most difficult case is supporting the maximum propagation delay at a 1-Mbps data rate, with a 40-m cable and isolated nodes, for example. Ideally, the bit time segments should be configured so that the sample point is as late as possible in the bit. For each integer total number of TQ in Table 1, one TQ must be allowed for the SYNC segment, and the PS2 (or TSEG2) segment must be large to accommodate the CAN-controller-information processing time (2 TQ for MCP2515, <1 TQ for ADSP-BF548 as long as BRP > 4). Also, for the MCP2515, PROP and PS1 can be 8 TQ maximum each; for the ADSP-BF548, TSEG1 (PROP + PS1) can be16 TQ maximum.

Figure 4 and Figure 5 show the possible total TQ configurations for MCP2515 and ADSP-BF548 respectively, with the latest sample point possible for the valid combinations of clock and BRP for 1-Mbps operation. The optimum total TQ for the MCP2515 is 19, requiring a hardware oscillator of 38 MHz and BRP of 1. For the ADSP-BF548, all the configurations except for a total of 5 TQ are at least 85% sample point, but the optimum setting is 10 TQ, requiring fSCLK= 50 MHz with BRP = 5.

Step 3: Match Transceiver/Isolation Delay and Bus Length to Configuration

Having achieved the optimum sample point for the CAN controller, the last step is to compare the allowable propagation delay with the CAN transceiver/isolation and bus length used. Assuming the ADSP-BF548 optimum configuration of 10 TQ (fSCLK= 50 MHz, BRP = 5), the maximum propagation delay possible is 900 ns. For the ADM3053 isolated CAN transceiver with integrated isolated power, the data-sheet maximum loop delay (TxD off to receiver inactive) is 250 ns. This must be doubled (500 ns) to include both transmit and receive delays at two nodes at the furthest ends of the bus.

Assuming a 5-ns/m cable propagation delay, a bus length of 40 meters (maximum for 1 Mbps per ISO 11898) could be accommodated with the ADSP-BF548 having a total of 10 TQ in bit time with only 1 TQ for the TSEG2 bit segment. In practice, slightly earlier sample points may suffice, as even an extreme transceiver propagation delay on one node would likely result in a simple retransmission (handled automatically by the CAN controller at the data-link layer), but the small delay between the CAN-controller I/O and the CAN transceiver makes it advisable to configure the sample point to the latest point possible.

Conclusion

Isolation adds robustness, but it will also add a propagation delay, in both transmit and receive directions. This delay must be doubled to account for two nodes in arbitration. If the allowed propagation delay in the system is fixed, then the cable length or data rate may be decreased if isolation is added. An alternative is to reconfigure CAN controllers to allow the maximum possible propagation delay to ensure that the desired data rate and bus length are possible, even with isolated nodes.

Signal Newspaper Santa Clarita

Signal& Bus Segments

References

Isolated Controller Area Network (CAN)—Video

Marais, Hein. How to Calculate the Controller Parameters for an Isolated CAN (Controller Area Network) Network to Run at 1 Mbps

O’Brien, Maurice. Designing Robust, Isolated I2C/PMBus Data Interfaces for Industrial, Telecommunications, and Medical Applications. Analog Dialogue, Volume 48, Number 3, 2014.

Watterson, Conal. AN-1123 Applications Note. Controller Area Network (CAN) Implementation Guide. Analog Devices, Inc., 2012.