I'm not sure this would be better on Electronics Stack Exchange.
I've seen a few questions similar to this, but pre BLE 4.2 days, before it was possible to have characters of greater than 20 bytes, but these questions are outdated now.
To anyone who's not aware, from BLE 4.2 onwards, you have been able to send far more than 20 bytes in a characteristic. So, if you've not come across this, I have successfully been transferring characteristics of 240 odd bytes between iOS and a Silicon Labs device for well over a year.
I have recently set up a Nordic embedded device and knocked up a Qt GUI to transfer data between the Nordic device and the Qt app running on Linux, using the Bluez stack. It will transfer 20 byte characteristics just fine.
So, I increased the Nordic's characteristics to 40 bytes, but Qt is not playing at all with it.
I am confident things are right at the Nordic end because if I use a little Android app and query the 40 byte characteristic it reads all 40 bytes. This makes me think that the issue is at the Laptop end.
I have various unknowns:
Is my laptop really BT4.2. It's hard to know as Linux calls it an unknown device and its USB vendor and type number tell me it's an Intel device, yet the IDs seem to give me multiple possibilities.
hciconfig tells me that I am running HCI Version 4.2 and LMP Version 4.2. That, to me, suggests larger characteristics should work.
Can Linux itself cope with characteristics of greater than 20 bytes?
Can Qt cope with characteristics of greater than 20 bytes?
I am running Mageia 6 and Qt Creator 4.2.1 with Qt 5.9.4 kit.
I have no Windows or iOS device with LE new enough for larger characteristics. Also, Windows is a bit of a pain when it comes to LE...
Edit:
btmon gives this when it receives a 40 byte chatacteristic:
ACL Data RX: Handle 3585 flags 0x02 dlen 27 #1026 [hci0] 577.032058
ATT: Handle Value Notification (0x1b) len 22
Handle: 0x0010
Data: 35303120546869732069732061206c6f6e672063
This is sending out a string from the Nordic:
"%1 This is a long characterstic %1",Messno,MessNo
MessNo gets incremented every time the Noridic sends out a message. This gets truncated to xxxx This is a long
So, this suggests to me that it's getting truncated either by the BT stack on the assumption that this is what the Qt app is digesting.
You should increase the MTU size from the nordic device. It has nothing to do with Qt.
Related
I'm seeing ~15ms of overhead when communicating with a microcontroller over RS-485 with a USB-to-serial converter, is there any way to minimize this overhead?
I have some debug and data collection python3.10 scripts that connect to a microcontroller via either USB or half-duplex RS-485 serial. I'm using PySerial in both cases and I am either passing it the address for the USB-to-serial converter to the controller directly (running on MacOS). Today I logged how long a command and response takes to execute at different RS485 baud rates (median of 1000 command/response cycles, min time is similar):
9600 baud - 32 ms
38400 baud - 16 ms
115200 baud - 16 ms
230400 baud - 16 ms
500000 baud - 16 ms
USB - 1 ms
I have scoped the signal # 115200 baud and the command + response takes 3ms max, so I while I would like this micro to burn in a pit I don’t think I can blame this particular problem on it. Since all my code is shared between the serial and usb tests, I'm left to believe that the majority of the overhead is coming from pyserial or my d-tech usb-to-serial converter.
From what I’ve seen a large number of the usb-to-serial adapters use the same FTDI chipset, so I’m not sure if I would actually get any improved performance by blindly choosing another converter. If someone knows better here please chime in.
I'm making a project with Esp32 whroom, so I bought the yj-16009 iBeacon DataSheet and I'm trying to get it to work as wireless Bluetooth proximity sensor like in this Video
I used the this code from the video and the esp32 is monitoring and showing BLT scanning results like this the results shown are after I turned off any BLT device around so first I don't understand what it is reading, and second after I turn on the iBeacon the results remain with the same range of numbers no matter if I get the iBeacon closer or farther, therefor I came to the conclusion that it doesn't recognize the iBeacon sensor for some reason.
I also download an app named LightBlue which does recognize the iBeacon sensor.
My question is if anyone knows how to make the esp32 recognize the iBeacon sensor. Another thing I tried to find any information about this sensor and there is no info about it anywhere. I have read on other questions here that it might need to be programmed somehow which I don't know how to do because there is no info online. So if anyone is familiar with this kind of sensor and can help me figure how to make the ibeacon to work like the video above as a Bluetooth Proximity device it would be a blessing.
The code you reference is just scanning for any BLE advertisements (iBeacon or otherwise) and printing out the RSSI signal strength of each detection. The reason you do not see the RSSI change when you move the beacon is because the ESP32 is probably picking up non-iBeacon adverts from your phone, laptop and other Bluetooth enabled devices in the vicinity which are not moving (there are more around you than you think!)
In order to make the device detect iBeacon only (and not all the other devices) you need to change the C code to do a few more things:
Access the bytes of the advertisement payload and use them as follows:
Compare the beginning of these bytes to see if they include the iBeacon byte sequence FF 4C 00 02 15
If the above byte sequence is not in the advertising data, ignore that detection — it is not an iBeacon advert
If it does include that byte sequence, decode the next 16 bytes as the iBeacon uuid, the next two bytes as the major and the next two bytes as the minor. See my answer here: What is the iBeacon Bluetooth Profile
Print out the identifiers along with the RSSI that the code already prints.
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.
I have an Android App that write several bytes to a Bluetooth device.
Looking on btsnoop_hci.log I see that, when a large amount of bytes are sent to the BLE device, the app use Prepare Write Request more times and then Execute Write Request: Immediately Write All.
Now my problem is how to perform this with a my application using a RN4870 module.
At this moment I can connect, read service and characteristics, and write using
CHW command as described in the manual when the there are few bytes.
But I cannot write as the remote BLE device expect when there are lot of bytes.
Thank You for support
Marco
This is the Microchip answer:
Hello,
The core specifications are handled by the firmware.
The user doesn't have access at this level, so is nothing you can set.
Regarding the long data question:
"Does RN4870 module support the Data Length Extension feature? "
RN4870 rev 1.28 support DLE, but partially. The normal packet size in BLE without DLE is 20 bytes.
With a standard DLE feature, the normal packet size should be 251 bytes.
However, in RN4870 Rev 1.28, the packet size is 151 bytes. So it is not a full implementation of the DLE.
The DLE feature (Data Length Extension) is embedded into the lower levels of the Bluetooth stack and there are no specific commands to enable or disable DLE. Essentially, if the peer device also supports DLE, then the DLE will be enabled.
So there are no specific (commands) that you need to do to increase throughput through DLE.
Regards,
In other words there is nothing to do!
In Android Application you can't directly set the DLE length, instead you should set the MTU size. Android Bluetooth stack will calculate DLE length based on the MTU. Maximum Data Length supported by BT protocol in 251, but can be between 27 and 251 depends on BT controller H/W capability. During connection BT Device will negotiate with peer device(If peer device support DLE) to set Maximum DLE size supported by both device.
To increase your throughput you can use the maximum supported MTU size of 512. Also you can write without response and do error check on data using your own logic like checking parity or CRC and re-transmit data from Application for better throughput.
I am working with HM10 BLE chip with Arduino. I am able to establish serial communication between the two. In the manufacturer manual from jnhuamao.cn, it says that for AT+DISC? , "...Before V535 max results is 6, Since V535 not limit"
AT+DISC? is the AT command for scanning nearby BLE devices. The firmware for my chips are V539 and V540.
However, I am only able only received maximum 6 devices as scan result in the serial monitor. And they are different everytime. (I have 8 chips powered up nearby). Has anyone ran into the same problem? What could be the problem? What might be the solutions?
THANKS A LOT
the number of discoverable devices for hm-10 is 6 devices in one go.
its in their datasheet.
Even im facing a similar issue.
Im looking for something that will give me upto 20 devices in the scann results.