In other words, can a router have more than one BSSID (for example, implementing two different versions of the 802.11 protocol)?
And if so, are the RSSIs from the BSSIDs of a specific router exactly the same?
Yes ,you can have multiple BSSID on single router (or card) by making
Multile VAP(virtual access point)
But , the RSSI should always be same for all new VAPs as RSSI depend on
Tx Power (output power) ,thus can set one output power per chip (router).
you can change output power (RSSI) for different VAPs (BSSID) if it have more
than one Wlan Chip inside .
Related
I have bee working with BLE for a while now, but primarily for reading and notifying characteristics.
The devices specifically are Virtual cycle trainers that support GATTS Cycling Power Service - 0x1818 link
I know that it's possible to increase resistance on this trainer, but I have read the documentation on Cycling Power Control Point - 0x2A66 [link][2] which is the only one with Mandatory write functions, but non of the documentation seem to be make sense.
Trainer: Cycleops Magnus
Reading and writing characteristic
// Reads all characteristics
var characteristics = service.characteristics;
for(BluetoothCharacteristic c in characteristics) {
List<int> value = await device.readCharacteristic(c);
print(value);
}
// Writes to a characteristic
await device.writeCharacteristic(c, [0x12, 0x34])
Reading and writing descriptors
// Reads all descriptors
var descriptors = characteristic.descriptors;
for(BluetoothDescriptor d in descriptors) {
List<int> value = await device.readDescriptor(d);
print(value);
}
// Writes to a descriptor
await device.writeDescriptor(d, [0x12, 0x34])
The closest I can see is setting the crank length, or chain weight but at this stage I am only guessing and am looking for some guidance.
The questions is this..
What characteristic or descriptor should I use to adjust Virtual Power
trainer resistance and what is the best way to do this?
Any coding Language is fine, I can transpose it.
Screenshot of services available for device
[2]: https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.characteristic.cycling_power_control_point.xml
I think you're using the wrong Bluetooth service for this. The Cycling Power Service is for collecting data from cycling power meters like this one: https://www.cyclist.co.uk/reviews/6705/long-term-review-fsa-powerbox-carbon-power-cranks
For your requirements, I believe you should be using the Fitness Machine Service (0x1826) which includes the Indoor Bike Data characteristic (0x2AD2) and most importantly for you, the Fitness Machine Control Point characteristic. Take a look at section 4.16.1 of the Fitness Machine Service specification and you'll see details of operations which the control point supports, including a reference to 4.16.2.5 Set Target Resistance Level Procedure. I think this is what you need.
You cannot use cycling control point(CPP) for adding resistance. CPP can only be used to copy data like wheel Revolution from old peripheral to new one or if you want to reset data on peripheral you can use cpp.
If you want to add resistance you need to check for fitness machine i am using elite and elite have Fitness Machine Control point you can write resistance and other things like inclination, elevation etc using FTCP.
Few of the vendor support fitness machine and other have given their api or source code you can use that to add resistance and other stuff like that.
Indoor trainers have a few services:
Cycling Power Service (ANT+ or BT also have)
ANT+FEC (ANT only)
BTLE Fitness control (FTMS)
TACX ANT+ FEC. over Bluetooth (https://blog.lazerwalker.com/2019/02/15/bike-game-part-2.html)
Wahoo's Extension to the Cycling Power Service (to be able to set Target power for instance)
To Add Resistance to the trainer to #1, you need to check if it also has the #5 service as well. (this is the UUID used - A026E005-0A7D-4AB3-97FA-F1500F9FEB8B)
#4 is actually a protocol which Tacx came up w/ before FTMS was a standard and some trainers still use this.
I want to use CANopen, and by the preconfigured set a device can have more than one COB-ID(as it has different function codes)
I want to know if the CAN bus frame identifier uses CANopen's COB-ID as it is.
A CANopen node cannot use multiple identifiers at the same time, but it's technically possible to reconfigure the node-ID. According to CiA301 - CANopen application layer and communication profiles, during NMT state initialization the parameters of the manufacture specific profile area and of the standardized device profile area are set to their power-on values.
One way to implement this is to assign a default node-ID for the CANopen node. Then reserve a SDO object in the object dictionary to modify the node-ID after reset or power-on. Note that if you want to fully follow CANopen standard, when you change the node-ID, the CAN-ID allocation modify the IDs for the other NMT states and communication objects such as SDO, PDO, etc.
Check this link for further information.
I want to be able to detect when a peripheral sensor is NOT connected to my Raspberry Pi 3.
For example, if I have a GPIO passive infrared sensor.
I can get all the GPIO ports like this:
PeripheralManagerService manager = new PeripheralManagerService();
List<String> portList = manager.getGpioList();
if (portList.isEmpty()) {
Log.i(TAG, "No GPIO port available on this device.");
} else {
Log.i(TAG, "List of available ports: " + portList);
}
Then I can connect to a port like this:
try {
Gpio pir = new PeripheralManagerService().openGpio("BCM4")
} catch (IOException e) {
// not thrown in the case of an empty pin
}
However even if the pin is empty I can still connect to it (which technically makes sense, as gpio is just binary on or off). There doesn't seem to be any api, and I can't legitimately think of logically how you can differentiate between a pin that has a peripheral sensor connected and one that is "empty".
Therefore at the moment, there is no way for me to assert programmatically that my sensors and circuit is setup correctly.
Any one have any ideas? Is it even possible from a electronics point of view?
Reference docs:
https://developer.android.com/things/sdk/pio/gpio.html
There are lots of ways to do "presence detection" electrically, but nothing that you will find intrinsically in the SoC. You wouldn’t normally ask a GPIO pin if something is attached—it would have no way to tell you that.
Extra GPIO pins are often used to detect if a peripheral is attached to a connector. The plug for some sensor could include a “detect” line that is shorted to ground and pulls the GPIO low when the sensor is attached, for example. USB and SDIO do something similar with some dedicated circuitry in the interface.
You could also build more elaborate detection circuits using things like current sensing, but they would inevitably have to put out a binary signal that you capture through a dedicated GPIO.
This is easier to achieve for serial peripherals, since you can usually send a basic command and verify that you get a response.
Detection using solely the input line can be tough. First, you'd want to narrow the scope of the problem. Treat as not-present the condition of a sensor not being connected, the sensor being connected but not responding, or the sensor responding in an uncharacteristic manner.
So, if it is a digital sensor, then communicating with the sensor may be enough to tell if it is present or not (especially if checksums or parity bits are involved).
Some analog sensors also have specific specs on how it behaves when triggered. You can utilize deviation from those specs to determine if the sensor is not present.
If you have a digital sensor w/o any error checking on it's output, where you clock out data (so all 0s or all 1s is valid) or it's just a binary 1 or 0 for output, then you'd need external help. Same for most analog sensors.
This external help would be something where you put the system in a known controlled state, press a button, and it then checks the sensors for output within a specific range. To be absolutely sure, you'd want at least two different states, to ensure your digital or analog inputs didn't happen to be stuck at the correct state for your test.
Just about any other method would be external to the system. Using additional IO to "detect" a sensor could help increase confidence the sensor is there, but you could get false positives where all you've learned is that "something" is there - not necessarily the sensor you expect.
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 have a bunch of questions concerning Timing Advance in GSM :
When is it defined ?
Is it the phone or the BTS who's in charge of defining it's value ?
is it dynamic, does it depends on certain situations ?
Let's say that I figured out a way to get the exact value of the Timing Advance (GSM Layer 1 Transmission level) from the phone's modem :
In order to verify my solution, I'm supposed to put my phone over and over in a situation where he have to use/change the Timing Advance while I log its value...
How can I do that ?
Thanks
In the GSM cellular mobile phone standard, timing advance value corresponds to the length of time a signal takes to reach the base station from a mobile phone. GSM uses TDMA technology in the radio interface to share a single frequency between several users, assigning sequential timeslots to the individual users sharing a frequency. Each user transmits periodically for less than one-eighth of the time within one of the eight timeslots. Since the users are at various distances from the base station and radio waves travel at the finite speed of light, the precise arrival-time within the slot can be used by the base station to determine the distance to the mobile phone. The time at which the phone is allowed to transmit a burst of traffic within a timeslot must be adjusted accordingly to prevent collisions with adjacent users. Timing Advance (TA) is the variable controlling this adjustment.
Technical Specifications 3GPP TS 05.10[1] and TS 45.010[2] describe the TA value adjustment procedures. The TA value is normally between 0 and 63, with each step representing an advance of one bit period (approximately 3.69 microseconds). With radio waves travelling at about 300,000,000 metres per second (that is 300 metres per microsecond), one TA step then represents a change in round-trip distance (twice the propagation range) of about 1,100 metres. This means that the TA value changes for each 550-metre change in the range between a mobile and the base station. This limit of 63 × 550 metres is the maximum 35 kilometres that a device can be from a base station and is the upper bound on cell placement distance.
A continually adjusted TA value avoids interference to and from other users in adjacent timeslots, thereby minimizing data loss and maintaining Mobile QoS (call quality-of-service).
Timing Advance is significant for privacy and communications security, as its combination with other variables can allow GSM localization to find the device's position and tracking the mobile phone user. TA is also used to adjust transmission power in Space-division multiple access systems.
This limited the original range of a GSM cell site to 35km as mandated by the duration of the standard timeslots defined in the GSM specification. The maximum distance is given by the maximum time that the signal from the mobile/BTS needs to reach the receiver of the mobile/BTS on time to be successfully heard. At the air interface the delay between the transmission of the downlink (BTS) and the uplink (mobile) has an offset of 3 timeslots. Until now the mobile station has used a timing advance to compensate for the propagation delay as the distance to the BTS changes. The timing advance values are coded by 6 bits, which gives the theoretical maximum BTS/mobile separation as 35km.
By implementing the Extended Range feature, the BTS is able to receive the uplink signal in two adjacent timeslots instead of one. When the mobile station reaches its maximum timing advance, i.e. maximum range, the BTS expands its hearing window with an internal timing advance that gives the necessary time for the mobile to be heard by the BTS even from the extended distance. This extra advance is the duration of a single timeslot, a 156 bit period. This gives roughly 120 km range for a cell.[3] and is implemented in sparsely populated areas and to reach islands for example.
Hope this Answer the question:)
It's defined everytime the BTS needs to set the define the phone's transmission power, which happens quite often.
It's the core system (BTS in GSM) who totally in charge of defining it's value.
It's very dynamic, and change a lot. Globally, the GSM core system is constantly trying to find the exact distance between the BTS and the MS, so it constantly make a kind of "ping" to calculate it. The result of such operations is generally not that accurate since there are a lot of obstacles between the mobile and the BTS (it's not a direct link in an open space).
Such operations happens a lot, so use your smartphone. Simply.