creating a network for more than 8 nodes with exchangable clients

[azizg]

20160316_113235.jpgHi guys,

i have 20 nodes and a central in my network, that are very close to each other except central device ( All of nodes are in a approximately 20cmx40cm area). Any device of these 20 nodes should collect up some datas of nodes and send to the single client. So the network can include 1 Client and 20 Nodes, in which one of these nodes acts as central (client) to send out all of sensor datas in a table. This network must meet following conditions:

• The central device should communicate to only one device (Client device in 20 devices). Central device will always listen to network whether any device is available.

• All of 20 devices can be exist in network or none of them can be there. If there is only one device, then this device should inform the central.

• It should be fastly clarified whether there is any device in network and should be send out only a few bytes of data to the central.

I don't know whether it could be developed an algorithm, that helps to find out the client device in 20 nodes. Because this network includes more than 8 nodes and all of them should act as either client or slave. Has anybody an idea to solve this problem?

I think, that i can let the device to act as client, that is first supplied. But i am not sure.

I would be very appreciate, if anybody tells me, which solution will be better.

Note: I want to use nrf51 DK to realize this.

Thanks a lot,

aziz

[Anders Strand]

Hi. It was not easy to fully understand your needs. It was not clear what the client/central was, and if they were the same device or not. The drawing was helpful, but not all nodes were named. For example, it is not clear what the nodes colored red are. It is also not clear what the right part of the system is.

• Are all nodes in the system based on the nRF51?
• Does all the 20 sensor nodes only send data, or must they receive data as well?

If the 20 sensor nodes only send data, they can broadcast the data using BLE advertisements. These advertisements can be scanned with a BLE central/observer.

You can also use a proprietary protocol like ESB, and make all the sensor nodes primary transmitters (PTX). The client will be a primary receiver (PTX). There is 8 pipes, but you can have all 20 devices use the same pipe.

If all sensors are this close, can you not simply wire them together?

Update 31 March, 2016, after some more information:

Using BLE is possible. You can create a scheme where the 20 sensor cards advertise their status and sensor reading. The central will scan for these advertisements, and use the data received. If the central wants to write some data to a sensor, it can connect to it, write, and then disconnect.

By using BLE, you get encrypted data data transmissions while you are connected.

As mentioned above, ESB is also a fitting protocol for your case. You can have the sensor cards send a transmission where it expects an acknowledgement. The central will send an acknowledgement when it receives the status update, and can also send data back. As mentioned above, you must use the same pipe (radio address) for all 20 sensor cards, but you can implement your own adressing scheme in the application.

ESB does not implement encryption by default.

-Anders