How many devices can be connected to at one time via Bluetooth using the BLE firmware on Android?
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A search of the Android Bluetooth Firmware source shows the following:
Max concurrent active synchronous connections (BTA_GATTC_CONN_MAX):
- 4 on Android 4.3
- 7 on Android 4.4+
Max concurrent active notifications (BTA_GATTC_NOTIF_REG_MAX):
- 4 on Android 4.3
- 7 on Android 4.4
- 15 on Android 5.0+
As a comparison my experience with iOS is that 8 devices can be connected at at time.
I tried connecting more than 7 devices the other day on Android 7.1 and Bluetooth stopped responding. Starting and stopping didn't help; the only thing that fixed it was restarting the device.
After working with several apps that connect to 4+ devices I can say from experience that these numbers are theoretical. Depending on each individual device and its hardware you'll have an easier or harder time connecting to and maintaining a connection to the maximum number of BLE devices.
Bryan Bryce
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Follow Bluetooth at Wikipedia,
A master Bluetooth device can communicate with a maximum of seven devices in a piconet (an ad-hoc computer network using Bluetooth technology), though not all devices reach this maximum.
You need know Master/Slave in Bluetooth first.
I think the good answer depend on your aim.
You're right when you know "can communicate with how many devices" depend on Hardware (Bluetooth Chip).
Bluetooth chip on Apple iPhone 4, 5 or Samsung Galaxy S3, S4 ... totally different with Basic Bluetooth Chip.
In my case :
I'm working with Firmware side related to BLE.
His peripheral device has used Basic Bluetooth Chip since it did not has enough memory to store many capacities as many features, likes Bluetooth chip on Apple iPhone 4, 5 or Samsung Galaxy S3, S4 ....
Therefore, his peripheral device only paired with one device in one time.
Thanks,
Huy Tower
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1Can someone else confirm this? This would be a limitation imposed via the Android OS as the hardware should be able to handle more. – Tim Tisdall Jan 16 '14 at 14:01
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2I'm more confused now. BLE doesn't have any concept of piconets, only regular Bluetooth does. I've connected 7 sensors with one bluetooth dongle via BLE all at once, so I know that BLE is capable of more than 1 device at a time. So, any limitation would be in the OS and you haven't referenced anything saying that Android is limited to one device. Also, reTs has connected 4 devices with an Android device, so I'm thinking that it's possible to connect to more than one. – Tim Tisdall Jan 20 '14 at 14:54
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@Tim Tisdall : hello Tim, u already check this case? How many devices u can connect in the same time? – Huy Tower Apr 06 '15 at 08:41
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Did you already read what I wrote? What part needs clarification? – Tim Tisdall Apr 06 '15 at 14:53
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so u mean u still not know how many devices we can pair via ble? – Huy Tower Apr 07 '15 at 02:52
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Read my comment again and read the answer I posted. I'm not sure what part isn't clear to you. – Tim Tisdall Apr 07 '15 at 13:25
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Ah, I don't know u already post the answer. I don't understand why u always told me read your comment. lol =)) – Huy Tower Apr 08 '15 at 01:36
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Both of the answers here are wanting so I thought I should add one:
There are connection limitations built in to the different BLE hardware. I think the lowest I've encountered is 3 connections at once and the highest was about 12-13 connections. These were limitations due to the design of the hardware and had nothing to do with the OS being used, though. Usually the limitation is due to the fact that the hardware has to keep track of certain data and there's a limited amount of memory in the hardware.
So, I don't know specifically for Android, but it doesn't make much sense for a limitation to be imposed at the OS level. Likely when you try to make a connection, and you've reached the limit due to the hardware, you should receive some sort of error/exception preventing the new connection. I think there's actually a "connection limit" error in Bluetooth, but some hardware gives other exceptions like "out of resources". Again, I'm not sure how that gets reflected on the Android level.
Tim Tisdall
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I come into BLE development without any knowledge in Classic Bluetooth development and I really don't know what "pair" means in BLE. Isn't that something only exists in Classic Bluetooth?
If you are talking about connection, when Android 4.3 first came out I made a few test on the SDK on Nexus 7 2013. The maximum number of devices it can connect is 4. I didn't test if this number changes in 4.4, but I can confirm it will not be anything less than 4.
reTs
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I think the number of connections is dependent on the hardware used and not the OS. So, it's possible to have a device that would have less than 4 or more. I don't think there's any in-built limit in the Android OS, but I don't know that for certain. – Tim Tisdall Jan 17 '14 at 17:54
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I use 4 as a reference. I am successful in connecting 4 BLE peripherals on any BLE enabled Android devices on my hand. I didn't test if the limitation is something larger than 4 on other devices, though. – reTs Jan 22 '14 at 09:20
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For every system, be it any firmware or OS like Android or iOS, there is a configured maximum concurrent connection limit. But in reality the connection parameters of each connection play a very important role in determining weather or not the system will be able to achieve that many concurrent connections.
For example, if the configure connection limit is 4 then the system can not have more than 4 concurrent connections. But if all of the connected devices are demanding a higher connection interval(say a 50mS connection interval) then the system may not be able to support all of them. This results in either some of the connections dropping out or not being able to connect entirely. But if the connection parameters are a bit relaxed(say a 1sec connection interval) then all the connections can be serviced properly.
Prasad Rane
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