After Bluetooth device A and Bluetooth device B are connected, use A to send data to B twice, the first time send 1, the second time send 2. Is it possible to receive data only once in B, and the received data is 12。
Hopefully bluetooth experts can provide some answers，thanks a lot！
Related
I want to know what does bluetooth transmit when it is just visible, not connected. I googled , I saw it transmit name of the device and mac address but just them ? Can we add some extra datas or can we change them dynamically ?
For classic Bluetooth (i.e. pre Android API level 21), you are restricted with the data that you can send in the inquiry response (which is connection-less data sent over the air). There are three types of inquiry response data that can be sent over the air:-
Inquiry Result:-
Inquiry Result with RSSI:-
Extended Inquiry Result:-
In other words, depending on what the scanning device asks for, the result can be different, and even though in all cases it is not just name and mac address, you cannot add just random extra data to the inquiry response.
For Bluetooth Low Energy (i.e. Android API level 21 and later), advertising data can be dynamic and can be configurable. The minimum advert report can only contain the device's Bluetooth Address (either the public or the random address). In other words, even the name of the device is not a requirement. However, it is usually common to include both the address and the name as this gives more information about the advertising device.
You can read more about this in the Bluetooth Specification v5.2, Vol 6, Part B, Section 2.3.1 (Advertising PDUs). Also have a look at the links below for more information:-
Is a BLE advertisement required to provide a non-empty local name
How BLE works: advertisements
BLE advertising primer
Screen grab from WireShark showing traffic when problem occurs
Short question - Referring to WireShark image, What is causing Master to send LL_CHANNEL_MAP_IND and why is it taking so long?
We are working on a hardware/software project that is utilizing the TI WL18xx as a Bluetooth controller. One of the main functions of this product is to communicate with our sensor hardware over a Bluetooth Low Energy connection. We have encountered an issue that we have had difficulty pinpointing, but feel may reside in the TI WL18xx hardware/firmware. Intermittently, after a second Bluetooth Low Energy device is connected, the response times from writing and notification of one of the characteristics on one of the connected devices becomes very long.
Details
The host product device is running our own embedded Linux image on a TI AM4376x processor. The kernel is 4.14.79 and our communication stack sits on top of Bluez5. The wifi/bluetooth chip is the Jorjin WG7831-BO, running TIInit_11.8.32.bts firmware version 4.5. It is based on the TI WL1831. The sensor devices that we connect to are our own and we use a custom command protocol which uses two characteristics to perform command handshakes. These devices work very well on a number of other platforms, including Mac, Windows, Linux, Chrome, etc.
The workflow that is causing problems is this;
A user space application allows the user to discover and connect to our sensor devices over BLE, one device at a time.
The initial connection requires a flurry of command/response type communication over the aforementioned BLE characteristics.
Once connected, the traffic is reduced significantly to occasional notifications of new measurements, and occasional command/response exchanges triggered by the user.
A single device always seems stable and performant.
When the user connects to a second device, the initial connection proceeds as expected.
However, once the second device's connection process completes, we start to see that the command/response response times become hundreds of times longer on the initially connected device.
The second device communication continues at expected speeds.
This problem only occurs with the first device about 30% of the time we follow this workflow.
Traces
Here is a short snippet of the problem that is formed from a trace log that is a mix of our library debug and btmon traces.
Everything seems fine until line 4102, at which we see the following:
ACL Data TX: Handle 1025 flags 0x00 dlen 22 #1081 [hci0] 00:12:48.654867
ATT: Write Command (0x52) len 17
Handle: 0x0014
Data: 580fd8c71bff00204e000000000000
D2PIO_SDK: GMBLNGIBlobSource.cpp(1532) : Blob cmd sent: 1bh to GDX-FOR 07100117; length = 15; rolling counter = 216; timestamp = 258104ms .
HCI Event: Number of Completed Packets (0x13) plen 5 #1082 [hci0] 00:12:49.387892
Num handles: 1
Handle: 1025
Count: 1
ACL Data RX: Handle 1025 flags 0x02 dlen 23 #1083 [hci0] 00:12:51.801225
ATT: Handle Value Notification (0x1b) len 18
Handle: 0x0016
Data: 9810272f1bd8ff00204e000000000000
D2PIO_SDK: GMBLNGIBlobSource.cpp(1745) : GetNextResponse(GDX-FOR 07100117) returns 1bh cmd blob after 3139=(261263-258124) milliseconds.
The elapsed time reported by GetNextResponse() for most cmds should be < 30 milliseconds. Response times were short when we opened and sent a bunch of cmds to device A.
The response times remained short when we opened and sent a bunch of cmds to device B. But on the first subsequent cmd sent to device A, the response time is more than 3 seconds!
Note that a Bluetooth radio can only do one thing at a time. Receive or transmit. On one single frequency. If you have two connections and two connection events happen at the same time, the firmware must decide which one to prioritize, and which one to skip. Maybe the firmware isn't smart enough to handle your specific case. Try with other connection parameters to see if something gets better. You can also try another Bluetooth dongle from a different manufacturer.
My question is not related to the software, but to the technology. I think BLE is the solution to my system, but I am not sure how it works, how the pairing works.
I am projecting a system with 4 devices, each one with some sensors.
Devices A1 and A2 have same sensors, they are independent each other and read different data. If one of them read a critical value, it makes a noise.
Devices B1 and B2 have same sensors, they are close and are dependent each other. I mean, I need to know if the value of B1 is higher than B2 or viceversa. The device with the higher value makes a noise.
---- ------------ ----
|A1| ------> |smartphone | <----- |B1| <--|
---- ------------ ---- |
^ ^ |
---- | | ---- |
|A2| ----------| |----------- |B2| <--|
---- ----
These devices are all close by each other, and will synchronize later, just at the end of the day, to a smartphone to store all the data read.
How can I make the connectivity among sensors and smartphone?
I need to make communicate B1 and B2, to know who has the higher value.
Then I need to make communicate all of them to a smartphone to collect data.
Is one chip Bluetooth Low Energy for each device enough ? Can I use the same chip to communicate between devices, and with the smartphone (in different moments) ?
I am not sure about the pairing process... should I need to associate and disassociate devices to the smartphone each time? Or it's better to have B1 as master with 2 chips BLE, one for the smartphone and one to communicate do B2?
BLE requires that one device be a server, the other the client, in order to establish a connection. You cannot have a server talk to a server, or a client talk to a client. However, devices can implement both server and client protocols.
If B1 and B2 are identical, and they only implement either server or client interfaces, then they cannot talk to each other. If you have design control over B1 and B2, you can design them to implement both server and client protocols and then automatically talk to each other to update each one on who has the higher value. However, I wonder why you need to have them talk to each other at all - why can't the smartphone get both B1 and B2 values, then decide which to keep? It could then also send a command to B1 or B2 to make the noise.
A single BLE chip can manage many connections, since BLE connections are very temporary (and, if the internal software supports it, it may be able to handle multiple simultaneous connections).
If the decision about which I would have B1 and B2 simply include their measurement data in their advertising packet, and then have both listen to the others advertising packets. In this case, there is no need to establish any negotiated connection at all - each device is just running a BLE "nearby devices" scan continuously. Then, when the smartphone comes by, they can each establish a negotiated connection with the phone independently and upload their data.
I am new to Arduino and I have 2 issues when I tried the BluetoothShieldDemo.
I can only send data from bluetooth module(through serial monitor) to phone but I cannot send from phone to bluetooth module(to display it in serial monitor). I used oscilloscope to check there is signal in the Arduino board RX pin but no data display in the serial monitor. I suspect it is an IO issue so I changed the IO from digital pin 6 and 7 to digital pin 2 and 3, then digital pin 4 and 5. But it is still not working. Then I change the code to use hardware serial (Serial1) and it is working now. I just wonder why it is not working with the SoftwareSerial.
Although I can send and receive data, I cannot change the bluetooth name. The bluetooth module has no response when the below commands are sent. Is it the bluetooth module is in some kind of locked mode? Or the command is different from manufacturer? The bluetooth module that I got has a single CSR 31A2 chip on it. But the other shield that I saw on the web has 2 chips and it is with CSR BC417.
Codes:
blueToothSerial.print("\r\n+STWMOD=0\r\n");
blueToothSerial.print("\r\n+STNA=BluetoothSlave\r\n");
blueToothSerial.print("\r\n+STOAUT=1\r\n");
blueToothSerial.print("\r\n+STAUTO=0\r\n");
delay(2000);
blueToothSerial.print("\r\n+INQ=1\r\n");
Thanks in advance!
1- When using SoftwareSerial, how are you declaring the pins (Input/Output)?, Are you pulling serial data right (giving it enough time between data transmission, but reading at the right time)?
2- Find the datasheet of your module and see what commands does it support.
I'm working on a project with Android and Arduino and am trying to figure out how on the Arduino side to tell if the Bluetooth is connected or not.
I'm using one of these Bluetooth Modules to connect. I know I can send a command through Android, but I'm trying to have an action happen automatically when they connect and not have to run a background application on the Android if possible.
Using the module supplied and nothing else you cannot: notice the module has four connectors:
Power (Vcc)
Ground
Tx (send)
Rx (receive)
Given this interface the only way to determine whether the bluetooth module is paired is to send something to the paired device and have it respond in such as way that your Arduino knows that it is connected. For instance, if your Android program always responds with "Hi there!" when it receives a string "Hello?", then by seingin "Hello?" your Arduino will know that it is paired with your Android phone/tablet. Your Arduino could poll (send the interrogation string) every minute (or every five seconds) to see if it is paired with your device.
There is a better way, but it will require some soldering on your part. If your module is HC-03/HC-05-based, then the PIO9 pin is the "paired indicator LED" (see datasheet here). You could connect that pin to an Arduino input pin and read the level: reading digital 1 will indicate that the device is paired, while reading digital 0 will indicate that it is not. It is possible, though not certain, that the pin on your module labeled STATE is exactly this kind of a pin, i.e. it indicates the paired status. Unfortunately. this pin it isn't connected to the header, so you'll have to solder a wire to the correctponding pad to connect it to your Arduino. You should test it first by connecting a multimeter in voltage mode to that pad and measure the potential between that pad and ground in paired and non-paired state. If this is the pin that responds to the paired state then you are golden. It might be that it indicates power (like the HC-03/05 PIO8 whilc blinks when on). If it turns out that the STATE pin is not the pairing status, then you should request a datasheet from your supplier, and use that to find the status LED connection: one is likely to exist. Once you found the correct pad, verify its function using the voltmeter again. Then solder a wire to that connection and read it from your Arduino.
IMPORTANT: Make sure that your Arduino never puts out a digital 1 on the Arduino pin connected to the bluetooth module status pin: these bluetooth modules run on 3.3V, and connecting any unprotected pins to 5V will be damaging. The Vcc and Txd pins are voltage shifted in the module you bought, but the LED/Status lines are likely not to be. So if the Arduino pin connected to "status" on your Bluetooth module is configured as output and you digitalWrite(HIGH) to it, you will likely damage the Bluetooth module.
Unfortuntaely, the HC-05 will switch states when paired, but won't output a 1 until it's actually connected to something.
For instance, I can unpair my phone from the HC-05, pair again, and then the LED will change state, but the output of the STATE pin is still 0. If I open up an app, and connect to the device manually then the LED, and STATE pin will change state. The LED will periodically blink twice, and the STATE pin outputs a 1 to the Arduino.
If you would like to read the the value of the STATE pin, connect a wire to any of the inputs to the arduino, and code Serial.println(digitalRead(inputPin)); inputPin being the wire to the input of the Arduino.
I've been fighting this thing for months, and have yet to find a way to make this thing automatically connect to my phone. It won't even allow for me to connect to it from my phone to the HC-05 unless I download an app onto my Android. It's possible to bind the HC-05 to a certain address, but even this did not work for me. I want to mess with the "AT+CLASS" command, but the documentation behind the instruction has hindered me thus far.
From the HC-05 datasheet we see that the connection status depends on the output from PI09. Apparently sending "AT+BIND?" to the module will return the status of PI08 & PI09 in the form,
"+ POLAR=PI08,PI09" however this makes no sense to me because in order to get this you must enter AT mode and entering AT mode will disrupt the paired connection, hence it will always send PI09 marked as "not connected".
THUS in order to see if the connection is still live from the arduinos POV I can only see 2 feasible ways:
Program arduino to, every so often, send a "hello?" and if it doesn't receive the expected "Hi back" response, then it is to assume that it isn't connected.
Connect PI09 to an arduino input pin and read it's value whenever you want to check if the connection is live or not
AT+STATE? will return the current state of the connection. Yes you will need to enter at mode, that is done by bringing up pin 11 HIGH on the HC05 module. It does require soldering but it's kinda worth it. It then allows full AT control of the device, then set it LOW to return it to normal working mode.
Another option, which I don't fully understand, is the AT+MPIO? command, which returns the state of all the pins in some strange masked format I don't understand yet.
I use the first option above so that I can terminal (Bluetooth) from my phone to the HC05 and switch on a led/relay etc (ie bring up pin 2 to HIGH) on the HC05. This required entering AT mode (pin 11 HIGH), sending the command AT+PIO=2,1 and then setting pin 11 to LOW to return to normal working mode.
Note: I noticed I had to put a 200ms delay in between high and AT and LOW commands. Angela's solution is nice - I use a cheap XBEE Bluetooth module (HC-05 Bluetooth Bee Master & Slave Module with Bluetooth XBee for Arduino uk2015) 2 units(HC05/6) for 5Stg which are laid out in XBEE format - handy for the 3.3v.