I search for a wifi interface which accept master mode for create Access Point with Hostapd and can handle at least 40 stations connected (for a classroom)
Hostapd provide the "max_num_sta" but the real limitation is with the hardware?
Do you know wifi interface which accepts a large number of stations in master mode?
Related
By the Omnet++ 6 and then Inet 4.4 framework:
I want to simulate a WiFi network that includes some nodes, each node has several radio interfaces for example two radio interfaces,
Can I get the RSSI value when a packet is received in the MAC layer? If the answer is yes, how to get the RSSI value? Should the amount of the RSSI be calculated by each radio interface that received the packet?
How about in the network layer?
Please include the necessary code in addition to the explanation.
Thanks in advance
Ad. 1. In MAC layer it is possible to get the power of the received signal - take a look at OMNET++: How to obtain wireless signal power?. The RSSI is proportional to the power of the signal, however the IEEE 802.11 standard does not specify how the RSSI is related to that power. It is vendor specific.
Ad. 2. The power of received signal as well as the radio interface ID are available for developers in the network layer - in the same way as presented in the mentioned answer.
Iam trying to get data from HP switches and Juniper firewalls and its port via snmp.
I am looking for the way how to analyze live traffic on port so I can create a graph of utilization of the ports like on Solarwinds or Observium.
So far I have the results I am getting are from the formula on How to calculate traffic on cisco
It works fine, however, every couple of readings I get abnormal speeds. I.e. for a virtual interface on the firewall, which is limited to 4MB I get 20+ MB every now and then.
I have a cron job which polls the devices every 5 minutes so the formula is using 300 seconds as a delta of time.
So the question is, is it possible for a port to be showing these abnormalities or am I doing something wrong? Any insight would be amazing :-)
The problem is that you are using ifTable defined in RFC1213. It is sort of outdated due to ifInOctets and ifOutOctets are defined as 32-bit counters. So they will overflow and reset real fast and you'll face abnormal results when this happens. I'd suggest switching to ifXTable (IF-MIB) where these counters are defined as 64-bit values.
I am trying to set up my Intel Nuc as the Onboard Computer for using DJI OSDK on my Matrice 100. I am looking for suggestions to find a way to power the Nuc from the Matrice.
In the beginning, I connected a DC-DC voltage regulator to one of the XT30 ports to get 19V and power the Nuc. It worked okay for a while and I was able to fly the Matrice outside using OSDK. But it has suddenly stopped working now. When the Nuc tries to boot into Ubuntu, it shuts down abruptly.
In short, use separate power source for Onboard PC and sensors.
Typically sensors and PC such as IR or LIDAR or NUC draws power heavily. If the current changes, the sensor value will change (which is bad). The PC will need a safe margin of voltage e.g 16 to 21. A sudden gust wind can cause the drone to output thrust power at a maximum which might lower the voltage for couple secs. In this case, PC might gets shut down or provide wrong calculation output ( e.g false odometry output)
So adding a stand-alone small size 5 cell battery should give you stable performance. Here I cant promote a specific commercial item. For my project, I bought the battery from Hobbyking to do the job for onboard PC and Kinects. You can search there for the battery that suits your need
PS. don't get DC to DC converter, typically it is very low efficiency and prone to power disturbance. I use typically raw battery and BEC(for 5V or 12V Sensor such as IR sensor and Hokuyo LIDAR)
I have a heating control device in my home that has two inputs marked NC and M (or COM?), which I read in the documentation I can use to control/switch the state of the device (it also says the input accepts 10V..). I think it means it would accept a switch between those two terminals. It also mentions it is isolated from the mains.
Being only a mediocre RPi3 user/developer, with little hardware hacking experience, I was wondering if the RPi3 GPIOs could be directly connected to those input terminals and make me able to change the state of the device. In which case, what GPIO numbers are best, how would they connect and what is the principle of programming this as I would prefer to use node-red and its GPIO nodes or the command line.
Imagine I have say 6 intelligent devices all connected together end to end with a data link (could be two serial ports per device). Each device has unique ID programmed into it and we want each device to work out where it is in the chain of devices. So with 6 devices my daisy might look like:
-[901]---[905]---[902]---[903]---[906]---[904]-
At the end of the 'discovery' algorithm each device would have the above map and know which device it is connected to on its left and right, if any for the end devices. Each device would operate the same software and be identical to each other, apart from the unique ID.
Is there an easy way to do this without it getting too complicated ? The number of devices in the chain could be variable but a maximum of 6.
This sounds very similar to ARP resolution. Since there is a maximum of only 6 devices, a basic algorithm of broadcasting the request to the network (i.e. each device) would probably be the simplest way. Likewise, linearly passing the request wouldn't take much longer either.
If they are network devices with MAC addresses, you can even take advantage of these unique IDs instead of creating your own, if that's useful.