Questions tagged [digital-communications]

Related to all communication systems that use a given digital sequence as an interface between the source and the channel input.

Digital communication systems, by definition, are communication systems that use such a digital sequence as an interface between the source and the channel input (and similarly between the channel output and final destinaton).

Reference Document

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Why does USB have 4 lines instead of 3?

USB specifies 4 pins: 1. VBUS +5V 2. D- Data- 3. D+ Data+ 4. GND Ground Why is this not 3? Could the Data and Power not share a common ground? Am I correct in understanding that D- is the ground for D+ ?
Mark Harrison
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Why is digital serial transmission used everywhere? i.e. SATA, PCIe, USB

While looking at SATA, PCIe, USB, SD UHS-II it struck me that they are all the same: digital serial bitstream, transmitted using differential pairs (usually 8b/10b coded), with some differences in link/protocol layers. Why so? Why did this become…
artemonster
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SPI or I2C: which to use for a longish bus

I'm contemplating a project that would require several AVRs talking to each other over a bus. They'd be separated by as much as 6 feet. It seems like both I2C and SPI can let a series of micros communicate over a bus, but I haven't seen anything…
edebill
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Can a premium HDMI cable outperform a standard cable?

Assuming two cables both conform to the same standards (e.g. HDMI2.0, high-speed, ...) is it possible that a premium cable will outperform a standard cable when using an objective benchmark that measures the quality of picture/audio? Or what…
zr.
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I2C 3.3 to 5.0 V conversion

I'm trying to interface a 3.3V I 2 C device to a 5V Arduino. I don't have any problem with SCL line. I can use a simple voltage divider but I have an issue with the SDA line as this is bi-directional. I'm not at all sure how to handle this. I have…
JohnC
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Examples of fluid (including air) being used to transmit digital data?

We usually use electrons to communicate data across wires, and sometimes we use light also. Does anyone know of real world example systems that use fluids (including air) to do this, and the advantages vs using wires? When I search for air pressure…
Ryan Griggs
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Could data transmission power consumption be lessened by transmitting more zeroes?

According to the IEA 250 TWh of power was consumed in 2019 due to data transmission globally, about 1% of worldwide electrical power use. I would like to pose a very simple question regarding power consumption in data transmission. Does it use more…
Fiach Reid
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What is a Patty Code?

In my digital logic lecture today, my professor introduced a symbol code called Patty Code . I copied this table off the whiteboard: | Symbol | Binary | Odd Patty | Even Patty | |--------+--------+-----------+------------| | a | 00 | 100 | 000 | | b…
Winny
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Is there any way to use half-bits?

As most people here know, by using 4 bits, we are able to count from 0 to 15 (0123456789ABCDEF in hexadecimal). But if we were to only count up to 9, we would still be using 4 bits, and the digits from A through F would be wasted. However,…
Galahad78
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transmitting 5v signal over a long cable

I'm seeking for help here as I need a reliable answer to this. I need to get an input signal (low frequency 5v digital pulse ), to a micro-controller from a (proximity) sensor situated in a distance from the control board. I'll itemize the important…
Codenamed SC
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Data transmission protocol with two lines and no explicit clock

Are there communication protocols that transmit bits using two lines A and B as follows: When line A is toggled, a 0 is sent. When line B is toggled, a 1 is sent. I currently use this to push out debugging info from my µC projects, because is…
Nordic Mainframe
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HDMI and I\$^2\$C

I was having a look at the HDMI pinout and I thought: why would they use I\$^2\$C for the display-host communication? My question here is about the design metrics that lead to this choice. HDMI is a quite recent standard while I\$^2\$C is around…
Vladimir Cravero
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What does an SD Card do internally during the 74 clock cycles at startup

It is documented that the SD Bus Interface requires 74 clock cycles before the first command is sent: Taken from SD Specifications Part 1 Physical Layer, Simplified Specification, Version 6.00…
Graham
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Communication among briefcase halves

I'm building a small laptop-ish device in a briefcase. Imagine the green wires aren't there. The LCD half lies somewhat deeper in its case than the keyboard part. For now, testing and programming, I'm using four wires (2x I2C, ground, 5V) to connect…
user17592
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Why AT command set?

Frankly, Why do all communication ICs(or at least many of them or most famous or popular) such as Bluetooth or WIFI or GSM or etc support AT command set? why don't they have a simple pin for D/C(Data or Command) for communications? What are the…
Roh
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