Advertesiment

[Andhika]

Hi,

I'm currently wprking on my project, my project it's about swarm, before the master swarm can advertise the message to the slave swarm through blehandler function now we want to develop so we can send order from smartphone to the master, I'm facing the problem that the smartphone can't detect the connection because of blehandler function, can ble advertise to slave device while it established a connection with smartphone? should i build a Thread or a mesh?

[haakonsh]

We need you to rephrase your question because it is very difficult to understand what it is you want. 

What is a swarm?

"I'm facing the problem that the smartphone can't detect the connection because of blehandler function"
- what are you talking about here, what is the context? 

"can ble advertise to slave device while it established a connection with smartphone?"
You can use directed advertisements while in connections with another devices. The S140 supports up to 20 concurrent links, so that should not be an issue.

"should i build a Thread or a mesh?"
That depends on your use-case. What is your use-case, what is it that want to achieve with this project? 

[Andhika]

Hi haakonsh,

I'm really thankfull for your help, so my project is to advance the previous project it's about Drone-Swarm (so more than one drone with concept master and slave) the previous project has a function called BLEhandler that send message over BLE such as position etc. and now my job is i want to establish a connection with a smartphone so we can send an order such on/off, fly, back and forth to master drone. as i want to buid the connection with smartphone there is an interference from function BLEHandler, which i believe it advertise the message to the slave, so the smartphone can't detect my board, but if i comment the function it can detect my board.

but thanks you've answered a half of my questions.

"can ble advertise to slave device while it established a connection with smartphone?"
You can use directed advertisements while in connections with another devices. The S140 supports up to 20 concurrent links, so that should not be an issue.

any suggestion how to do it?

I sincerely appreciate your help.

[haakonsh]

If you have fewer than 20-30 devices then a pico-net using BLE is perhaps the best solution, above that number, I believe BLE Mesh might be better. 

It depends on what your requirements for the wireless links are. If you only need to send abstract commands and basic telemetry like battery service, GPS position, etc, and your latency requirements are not strict then a mesh network is a good idea. The throughput will be low, the latency will be high, but the wireless range and scalability with regards to the number of units in the network will be better in a meshed network. 

I do not recommend routed meshed networks like Thread and Zigbee as the time it takes to rebuild a routing table varies from ~30s to several minutes, even for small networks. This is important because if one router is lost to the network, due to an empty battery, FW crash, or it has simply moved outside of the wireless range, the routing table will have to be rebuilt before you can send data between devices. This is not an issue for flooded meshes like BLE Mesh that does not rely on a routing table but rather retransmitted broadcast/omnicast messages. 

I do not believe there are any smartphones that support Thread or Zigbee, but there is support for connecting to a BLE Mesh network through a Proxy Node. A proxy node can communicate via a regular BLE connection at the same time as being a part of the Mesh network. 
 

[Andhika]

Thank you for your fast respond we just have 3 Drones, and the commands that we send is to on/of the drone give order to fly back and forth and so on, is it still possible to do it with ble?

i am really gratefull four your kindness.

[haakonsh]

Oh, in that case, BLE is by far the best option. 

We have a simple example that lets you create a virtual UART over a BLE link, UART/Serial Port Emulation over BLE. You can also create your own service and characteristics. 

Our BLE stacks, the SoftDevices can support up to 20 concurrent links, so 3 links are not a problem. 

[Andhika]

-i already tried it once but i can't connect to the putty eventhough i followed the instruction and then i tried using the simulator in ses it can't read what i send, honestly i'm using laird dvk-bl654 based on nRF52680 chips.

-and it's possible sending the order to drone without uart? i've once discussed it with my supervisor, that we using directly ble as our uart so we installing the order directly on chips. that's what we want honetsly.

-i'm wondering instead building a mesh should i make it as central & peripheral? because the role of the 1st drone act as peripheral from smartphone and also as central (master) to another 2 drones, but as soon as the 1st drone flies it becomes slave.

thank you for your support i'm really a beginner on these but it's my chance to learn.

[haakonsh]

Andhika said:

-and it's possible sending the order to drone without uart? i've once discussed it with my supervisor, that we using directly ble as our uart so we installing the order directly on chips. that's what we want honetsly.

 You can use regular GATT services and characteristics to transfer whatever data you want, it does not have to be a UART bridge.

 

Andhika said:

-i'm wondering instead building a mesh should i make it as central & peripheral? because the role of the 1st drone act as peripheral from smartphone and also as central (master) to another 2 drones, but as soon as the 1st drone flies it becomes slave.

 There's no point in creating a meshed network with just three nodes, what you want is probably a pico-net. 

Andhika said:

because the role of the 1st drone act as peripheral from smartphone and also as central (master) to another 2 drones, but as soon as the 1st drone flies it becomes slave.

 Why don't you draw a graph of this network and the two states that you described, I did not understand to whom the 1st drone will become a slave to after it flies. 

[Andhika]

Sorry my bad, i was wrong, the first drone remain as a master even after it flies

it should look like this.

[haakonsh]

In our examples you can set the number of peripheral and central links the SoftDevice will support at compile time with the NRF_SDH_BLE_PERIPHERAL_LINK_COUNT, RF_SDH_BLE_CENTRAL_LINK_COUNT, and NRF_SDH_BLE_TOTAL_LINK_COUNT, found in sdk_config.h.

I suggest you look at the ble_app_uart example for how to create a custom service. If you do not know what a service and a characteristic is I suggest you google it, as there is plenty of resources that have described that already. 

I propose a service with one characteristic for battery status and another one for commands. If you have other needs such as Location, Intent, etc. you can add characteristics for that as well.

[Andhika]

thank for your help

so to be sure i sum up what we discuss,

for my connection problem caused by previous project function called BLEhandler (which i believe in advertising mode) i should either build a piconet or make my 1st drone act central and peripheral, is it sound right to you?

[haakonsh]

"either build a piconet or make my 1st drone act central and peripheral"
The first drone should act as both a central and peripheral. 

I see the definition of a piconet is outdated, as it now also encompasses BLE and not just EDR. With BLE you can have a piconet with any number of nodes, where any node can concurrently serve as both a central and peripheral in the same network, or in another network for that matter. 

The limitation for how many nodes a single node can connect to is given by the BLE controller it uses. The BLE controller in our S132 SoftDevice can connect to up to 20 nodes at the same time.