Which cables are best for gaming, cat5 e or cat7? I have top tier internet connection. So im just looking for latency to the minimum
As long as the cable is working correctly it has zero impact* on whatever workload you put on it. Gigabit is as fine over Cat.5e as over Cat.6 or Cat.7 or Cat.8.
*Not true with absolute precision: Cat.7 has a velocity factor (VF) of .79, so with a 100 m cable run it would actually save you 90 nanoseconds in comparison to Cat.5e (VF .66) each direction - or 9 ns for a 10 m cable. You might well round that off to zero though.
Related
I got a question about the data rate of the ethernet interface and hope someone can give me some hints on that.
I know the calculation method of the PCIe interface, for example, PCIe Gen3 X1 lane:
The data rate of single-lane should be
8 Gb/s (Gen3 line rate) * 2 (TX/RX, full-duplex) / 8 (to Byte) = 2 GB/s
(128/130 encoding is ignored)
So, how do we calculate the data rate of an ethernet interface?
Take 1000base-T for example, we have 4 twisted pairs, to sum up to 1Gb data rate.
So one pair should provide a 250Mb data rate. It’s full-duplex so TX/RX provides 125Mb each at the same time. With that being said, the “line rate” of a 1000base-T interface is 125MHz (125Mb).
Do I understand it correctly about the speedrunning on the ethernet interface?
how do we calculate the data rate of an ethernet interface?
Ethernet's nominal bit rate is generally defined at the top of the physical layer (L1). It includes preamble, SOF and IPG, but excludes all PHY-specific line encoding (PCS and PMA).
This is done to make all PHY variants of the same speed 100% compatible with each other. You can convert 1000BASE-T to 1000BASE-LX to 1000BASE-SX and back to 1000BASE-T without any buffer drops.
It’s full-duplex so TX/RX provides 125Mb each at the same time.
No - the nominal bitrate runs each direction, simultaneously for full duplex links. Each 1000BASE-T lane transports 250 Mbit/s worth of "user" data.
With that being said, the “line rate” of a 1000base-T interface is 125MHz (125Mb).
Since the line rate is (usually) the PHY rate it's 1000 MBit/s, four lanes of 250 Mbit/s each.
1000BASE-T does use a symbol rate of 125 MBaud since its PAM-5 modulation transports more than two bits per symbol. You might think that PAM-4 with exactly two bits would be sufficient, but the line code overhead eats up the rest. 1000BASE-T is already quite complex, it uses two-dimensional Trellis modulation plus scrambling to get across the wire (to produce a self-clocking signal, improve the signal/noise ratio and eliminate excess DC).
The 1000BASE-X PHYs for fiber are much simpler. The PCS uses 8b10b to produce a binary stream of 1.25 GBd that can be directly used to modulate the laser.
Morning Overflowers,
For a specific in-house application for my company, I need to be able to make a Gigabit ethernet connection go through DB15 connectors, as seen bellow.
Here is what I'm trying to achieve:
For the first version, I just cut in half a cat 5e ethernet cable. I did not care too much about the pin-out from the cable to the DB15 connector and in the end I ended up having a 10MBit/s data rate, which is super low. Also my cable was super short, 2m in total.
For the second version I used a 5m cat 6 cable for one side, and the remain of the other cat 5e cable (resoldered) for the other side. I was more careful about the pinout and used the 4 left most pins to place the ethernet pairs as seen here:
The data rate is this time 100 MBits/s, but still not 1 GBits/s.
Before going through a 3rd version I thought I'd use my brain a little. I noticed while soldering that although inside a cat 5e/cat 6 cable there are 4 pairs, not all of them are side by side on the RJ45 socket as seen on figure bellow where blue and green wires are a bit mixed.
There is probably a reason for that arrangement and putting pairs together other that inside the cable itself is not probably a good idea, which leads to my question.
For version 3, should I just keep pin 1 to 8 in that order and solder them to the DB15 connector on adjacent pins?
More generally I am aware that unless the DB15 section is super short I won't be able to maintain Gibabit ethernet due to noise and other problems caused by unmatched pairs on that section.
I am open to any suggestion or tips or anything :)
Thanks in advance
After trial and errors, it turned out that it works fine if you arrange pairs to match a RJ45 connector (like on the figure "ethernet plug wiring"). The quality of the cable is probably not the one of a perfect 5e/6 cable but my computer can negociate a Gbits connection and transfer files over the network at speeds way above 10 MB/s reaching 50 MB/s. I always soldered more section with various connectors and it worked fine too.
I have a project that consisted of transmitting data wirelessly from 15 tractors to a station, the maximum distance between tractor and station is 13 miles. I used a raspberry pi 3 to collect data from tractors. with some research I found that there is no wifi or GSM coverage so the only solution is to use RF communication using VHF. so is that possible with raspberry pi or I must add a modem? if yes, what is the criterion for choosing a modem? and please if you have any other information tell me?
and thank you for your time.
I had a similar issue but possibly a little more complex. I needed to cover a maximum distance of 22 kilometres and I wanted to monitor over 100 resources ranging from breeding stock to fences and gates etc. I too had no GSM access plus no direct line of sight access as the area is hilly and the breeders like the deep valleys. The solution I used was to make my own radio network using cheap radio repeaters. Everything was battery operated and was driven by the receivers powering up the transmitters. This means that the units consume only 40 micro amps on standby and when the transmitters transmit, in my case they consume around 100 to 200 milliamps.
In the house I have a little program that transmits a poll to the receivers every so often and waits for the units to reply. This gives me a big advantage because I can, via the repeater trail (as each repeater, the signal goes through, adds its code to the returning message) actually determine were my stock are.
Now for the big issue, how long do the batteries last? Well each unit has a 18650 battery. For the fence and gate controls this is charged by a small 5 volt solar panel and after 2 years running time I have not changed any of them. For the cattle units the length of time between charges depends solely on how often you poll the units (note each unit has its own code) with one exception (a bull who wants to roam and is a real escape artist) I only poll them once or twice a day and I swap the battery every two weeks.
The frequency I use is 433Mhz and the radio transmitters and receivers are very cheap ( less then 10 cents a pair if you by them in Australia) with a very small Attiny (I think) arduino per unit (around 30 cents each) and a length on wire (34.6cm long as an aerial) for the cattle and 69.2cm for the repeaters. Note these calculations are based on the frequency used i.e. 433Mhz.
As I had to install lots of the repeaters I contacted an organisation in China (sorry they no longer exist) and they created a tiny waterproof and rugged capsule that contained everything, while also improving on the design (range wise while reducing power) at a cost of $220 for 100 units not including batterys. I bought one lot as a test and now between myself and my neighbours we bought another 2000 units for only $2750.
In my case this was paid for in less then three months when during calving season I knew exactly were they were calving and was on site to assist. The first time I used it we saved a mother who was having a real issue.
To end this long message I am not an expert but I had an idea and hired people who were and the repeater approach certainly works over long distances and large areas (42 square kilometres).
Following on from the comments above, I'm not sure where you are located but spectrum around the 400mhz range is licensed in many countries so it would be worth checking exactly what you can use.
If this is your target then this is UHF rather than VHF so if you search for 'Raspberry PI UHF shield' or 'Raspberry PI UHF module' you will find some examples of cheap hardware you can add to your raspberry pi to support communication over these frequencies. Most of the results should include some software examples also.
There are also articles on using the pins on the PI to transmit directly by modulating the voltage them - this is almost certainly going to interfere with other communications so I doubt it would meet your needs.
I have been following a tutorial that enables you to play around with the TXPOWER parameter of your wifi card / wifi adapter:
http://null-byte.wonderhowto.com/how-to/set-your-wi-fi-cards-tx-power-higher-than-30-dbm-0149606/
You can easily boost up your wifi range when increasing the TXPOWER.
Now, most people want to improve their wifi signal strength of their home router, right. But in my case, I would like my home router (which runs on a raspberry pi) to have a relative small wifi signal radius (say, a radius of 2 meters), so that you actually need to physically look for the pi home router when trying to connect to it.
I have learned that this tutorial does not do a thing with the wifi link quality and/or the wifi signal level and thus does not influence the wifi radius of my pi home router.
link quality & signal level
Do you guys have any ideas/thoughts about how to decrease link quality and/or wifi signal level (e.g Link Quality = 12/70 and Signal level =-10dBm) ? Is this even possible ?
I am using a Tp-Link TL-WN722N IEEE 802.11n USB - Wi-Fi Adapter.
WIRELESS LITE N ADAPTER 150M USB HIGH GAIN 1DETACHABLE ANTENNA WL-AP.
150 Mbps - External
First, I recommend reviewing this section from your link:
QUICK DECIBEL UNDERSTANDING:
Every 10 decibels is a 10X increase in power starting from 1 dBm equal
to 1mW... 10 dBm equals 10 mW, 20 dBm equals 100 mW, 30 dBm equals
1000 mW, and so on. Every 3 decibels is approximately double that of
the prior power, so 30 dBm is 1000 mW, if we add 3 dBm, then we can
double the power such that 33 dBm is about equal to 2000 mW.
It appears to me that you are able to modify the transmit power of your adapter as the tutorial states. Are you saying this is not working? If you set your transmit power to something extremely low (-30dBm, for example) you would effectively be turning off the transmitter. Keep increasing that value until you get your desired coverage radius.
If the transmit power parameter is not functioning as per the tutorial, then there are other means to achieve reduced coverage. The model you specified has a detachable antenna....so detach it. This would definitely reduce your coverage. However, if it reduces coverage too much, you could simply add an inline attenuator. Fortunately, your antenna uses an SMA connector which is very common. You can find many SMA attenuators on ebay with different attenuation values. Experiment with different values until you get the desired coverage.
And if that doesn't work, just wrap a bunch of aluminum foil around the thing lol.
I'm new to Raspberry Pi and I don't understand about electricity. I bought a Raspberry B+ today and a 5V 3A power supply, but I'm afraid to connect it because in several places I read about using 5V 2A power supplies. I believe that only higher voltages can damage the Pi but, since I don't know about Amp, I don't know if this is true for 3A too.
My ideia is create a mini-personal server in my home, running Pidora. For data, I have a 1 Tb external USB drive with no external power supply (Seagate model SRD00F1).
My questions are:
can I use the 5V 3A power supply on Raspberry Pi B+ without damage it?
this power supply is compatible with my external USB drive to keep it on safely?
Thank you!
The Raspberry Pi FAQ says that the B+ uses between 0.7 and 1.0 amps, and suggest a 1.2 amp power supply as a minimum.
Using a power supply with a higher amperage rating will not harm your Raspberry Pi. Devices only draw as much current (amperage) as they need. Any additional capacity is unused.
This is where your question about the external hard drive comes in. If you see in the FAQ, they suggest that you might want a larger power supply if you use all of the USB ports. Every USB device you plug in is going to draw more current. To figure out how much you need, you just add up the requirements of all of the devices like so:
Raspberry Pi = 0.7-1.0A
Mouse/Keyboard = 0.5A
Hard Drive = 1.0A
========================
TOTAL = 2.5A
(These numbers are all fake... be sure to check the requirements for your actual devices.)
So if your devices total 2.5A then a 3A supply will handle all of these plus some room for expansion. If all of your devices total 3.5A, maybe you need to consider a bigger one.