I am trying to lower the transmitted Wifi power on a router running OpenWRT.
I've tried using the iw command to set the txpower to a very low 100 (1dBm)...
root#GL-iNet:~# iw dev wlan0 set txpower fixed 100
...and `iwinfo seems to report that the command was executed correctly...
root#GL-iNet:~# iwinfo
wlan0 ESSID: "Moonphase WAP"
Access Point: E4:95:6E:40:39:8C
Mode: Master Channel: 1 (2.412 GHz)
Tx-Power: 1 dBm Link Quality: unknown/70
Signal: unknown Noise: -92 dBm
Bit Rate: unknown
Encryption: none
Type: nl80211 HW Mode(s): 802.11bgn
Hardware: unknown [Generic MAC80211]
TX power offset: unknown
Frequency offset: unknown
Supports VAPs: yes PHY name: phy0
...but the actual emitted power does not seem to change no matter what I set the txpower to.
I've also tried...
using iw on the phy rather than the dev
setting the txpower in the /etc/config/wireless and rebooting
downing/upping the interfaces
...and none seem to have any effect on actual output power.
How can I pro grammatically lower the output power?
Notes:
I am aware of all the driver limitations in regulatory.bin, but I do not think these should matter here since I am trying to set a txpower that is lower than the county specific limits.
This router is a a clone of a TP-LINK TL-703N.
The router is running OpenWRT...
root#GL-iNet:~# cat /proc/version
Linux version 3.10.49 (alzhao#alzhao-ubuntu) (gcc version 4.8.3 (OpenWrt/Linaro GCC 4.8-2014.04 r42801) ) #6 Thu Oct 9 18:20:47 HKT 2014
The Wifi is handed by an AR9331 chip.
It turns out that the command...
iw wlan0 set txpower fixed 1
...does seem to set the radio to 1dBm, it is just even at this low level every client I have still shows 5 bars when in the same room. I had to take the receivers 30 feet away and on the other side of a wall for the lower signal strength to be visible.
Debugging this problem was compounded by the fact that the syntax for setting the power level inside /etc/config/wireless is different from the imperative form, so this is the format for setting it to 1dBm in the wifi-defvice section of the config file...
config wifi-device 'radio0'
option txpower '1'
Related
According to:
https://www.nvidia.com/content/dam/en-zz/Solutions/design-visualization/quadro-product-literature/proviz-print-nvidia-rtx-a6000-datasheet-us-nvidia-1454980-r9-web%20(1).pdf
the NVIDIA RTX A6000 uses up to 300 watts of power. It has a single 8-pin CPU power connector and of course it connects via PCI-E. In spite of what was once stated, the PCI-E 4, to the best of my knowledge, still only supplies 75w. With the 8-pin supplying at most another 150w, my math says 225w. Other high powered cards use two 8-pins for this reason I believed. What's going on with the $5k card?
njuffa's comment had the correct answer, but I cannot select a comment as correct.
An 8-pin CPU connector is different than an 8-pin auxiliary power connector.
https://www.pny.com/file%20library/company/support/product%20brochures/nvidia%20quadro/quadro-power-guidelines.pdf
In their power guide they show how to make an adapter for two 8 pin aux to an 8 pin CPU.
Due to temp (hopefully) financial problems I have to use old laptop. It's FSB (Front Side Bridge) clock is 333MHz (https://www.techsiting.com/mt-s-vs-mhz/). It has 2 SO-DIMM slots for DDR2 SDRAM. It had only 1 DIMM 2 Gb previously and it was a nightmare.
Each slot can handle maximum 2Gb so maximum amount of memory is 4Gb. Knowing that supported DDR stands for double data ratio, I've bought for funny money (10 euro) 2 DDR2 DIMM SO-DIMM 800MHz hoping to get (assuming memory divider is 1:2 - it's a double data ratio, isn't it?) 2x333MHz->apply divider=667MT/s (no idea how they have avoided 666). As I have Core2Duo I even had a very little hope to get 4x333MHz=1333MT/s.
But it seems that my memory divider is 1:1, so I get either
2x333MHzxDivider=333MT/s
4x333MHzxDivider=?
And utilities like lshw and dmidecode seem to confirm that:
~ >>> sudo lshw -C memory | grep clock
clock: 333MHz (3.0ns) # notice 333MHz here
clock: 333MHz (3.0ns) # notice 333MHz here
~ >>> sudo dmidecode --type memory | grep Speed
Supported Speeds:
Current Speed: Unknown
Current Speed: Unknown
Speed: 333 MT/s # notice 333MT/s here
Speed: 333 MT/s # notice 333MT/s here
~ >>>
So my 333MHz on FSB has been multiplied by 1 (one) and I've got 333MT/s (if I understood correct). I'm still satisfied: OS does not swap that much, boot process is faster, programs starts faster, browser does not hang every hour and I can open much more tabs). I just want to know, since I have Core2Duo what **MT/s8*8 do I have from these two? Or maybe it is even more comlicated?
2x333MHzxDivider=333MT/s
4x333MHzxDivider=667MT/s # 4 because of Duo
and is there any difference for 2 processors system with just 4Gb of RAM with MT\s == MHz?
PS BIOS is old (although latest) and I cannot see real FSB clock there, nor change it nor change the memory divider.
Looks like there's no point in checking I/O bus clock using some Linux command/tool because it is just always half of memory clock.
if what is written in electronics.stackexchange.com/a/424928:
I/O bus clock is always half of bus data rate.
my old machine has these parameters:
It is DDR2-333 (not standardized by JEDEC since they start from DDR-400)
It has memory MHz = 333
It has memory MT/s = 333
It has I/O bus MHz = 166.5 # just because
The thing I still don't get is that I have Core2Duo, so is my memory MT/s = 333 or 666.
how to use AT+CWLAP in esp8266 to get wifi signal strength? I want to get the signal strength which is displayed on the serial monitor and use it in my code in arduino IDE!
After sending the AT+CWLAP command, ESP8266 will answer with a list of all available AP's detected.
The format of the response will be like:
+CWLAP:<ecn>,<ssid>,<rssi>,<mac>,<freq offset,<freq calibration>
where:
<ecn>: indicates the security level, from 0 (OPEN) to 4 (Maximum security level)
<ssid>: it's the ssid of the AP
<rssi>: it's the signal strength, which is indicated in decibel format (e.g. -70)
<mac>: it's the MAC address
<ch>: channel
<freq offset>: ut's the frequency offset of AP，unit：KHz.
<freq calibration>: it's the calibration for frequency offset
So, the <rssi> parameter is what you are interested in.
Maybe, depending on the firmware version of your ESP8266, it's possible that AT+CWLAP command returns a different number of parameters, omitting, for example, the last four.
I use an ESP8266 dev board from NodeMCU with Lua. I power my chip with two AA batteries, which gives me 3V. See this:
https://www.hackster.io/noelportugal/ifttt-smart-button-e11841
How do I check the battery status using NodeMCU?
With a recent firmware you can use adc.readvdd33(). That should be enough for your case
I read somewhere that adc.readvdd33() was deprecated? Effectively it is for many of the ESP8266 modules available, the docs say, "If the ESP8266 has been configured to use the ADC for sampling the external pin, this function will always return 65535". So that means that any ESP8266 that has an ADC pin (like ESP8266-07 or -12, etc.) has this shunted in firmware.
But by adding a couple of resistors to make a voltage divider, you can still use the ADC pin for this.
[![schematics][1]][1]
[1]: http://i.stack.imgur.com/FEILF.png
Those resistor values will allow it to read 0-12V, as a value between 0-1024. (The voltage at the ADC pin must be less than 1V.)
val = adc.read(0)
Addendum: Adding this to your circuit incurs a power draw of approx. 0.01 milliamps, small but more than nothing. Multiply the values by 1000 to reduce it to infinitesimal. Or use 18 megaohm for r1 and 2 megaohm for r2, which divides the voltage by 10, and (wild guess) drains less current than most if not all batteries will attenuate when disconnected.
I am developing a handheld device based on IMX233 running embedded linux and is using Unifi CSR6026 for connecting to the WiFi networks. I have got the basic WiFi connectivity running using the wpa_supplicant and wpa_cli utilities. But i'm not able to detect when the user has entered a wrong key for the access point. The 'wpa_cli status' shows 'wpa_state=COMPLETED' and the iwconfig also returns the correct ESSID and MAC address of the access point as currently connected. Is there any other way to find out whether the user has entered a wrong key or not ??
root#freescale ~$ wpa_cli status
Selected interface 'eth0'
bssid=00:24:01:6a:3f:26
ssid=FirstFloorBGN
id=1
pairwise_cipher=WEP-40
group_cipher=WEP-40
key_mgmt=NONE
wpa_state=COMPLETED
root#freescale ~$ iwconfig
lo no wireless extensionsunifi1: unifi_giwencode: Surprise, do not have a
valid key index (0)
.
eth0 IEEE 802.11-b/g ESSID:"FirstFloorBGN"
Mode:Managed Frequency:2.422 GHz Access Point: 00:24:01:6A:3F:26
Bit Rate=24 Mb/s
RTS thr=0 B Fragment thr:off
Encryption key:off
Power Management period:500ms mode:All packets received
Link Quality=25/40 Signal level=-47 dBm Noise level=-72 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0
With WEP, there is no explicit key exchange, so there is no place in which a decryption error could be noticed. Your options are
switch to WPA
monitor the wireless statistics for decryption errors.
Note that the latter need not be an indication that the access point is using a different key.