how to know the channel i receive information from when i use nRF24L01 to connect between 3 of them

Question

i am using nRF24L01 to connect between 3 of them ( 1 is master and the others are slaves) and i am using nRF24 library , my problem is that when the master receive something from the other slaves and do not know from which channel the infromation come so is there is a way to know from which channel

//master channel code: const byte addresses[][6] = {"00001", "00002","00003"}; radio.openWritingPipe(addresses[1]); // mastr radio.openReadingPipe(2, addresses[0]); // carwl radio.openReadingPipe(2, addresses[2]); // carwl2

//slave 1 channel code : const byte addresses[][6] = {"00001", "00002","00003"}; radio.openWritingPipe(addresses[0]); // carw1 radio.openReadingPipe(2, addresses[1]); // mastr

//slave 2 channel code: const byte addresses[][6] = {"00001", "00002","00003"}; radio.openWritingPipe(addresses[0]); // 00003 radio.openReadingPipe(2, addresses[2]); // 00002

library i use: https://github.com/nRF24/RF24

Answer 1

You can pass theRF24.available function a pointer to a variable. The available function will write the pipe-number of the message to that variable.

An example can be found in the documentation

Answer 2

The nRF24 is highly versatile and can be programmed for a number of different network topologies. It appears you want either

1. One-to-many network - where the master node sends data to the slave nodes
2. Many-to-one network - where the master receives data from many slaves.

Both networks are achieved with the same radio channel (RF_CH) on all nodes.

For a one-to-many network you need to have a different RX address for each slave node. Set the master TX address to the RX address of the corresponding slave that you want to receive the data. Done.

For a many-to-one network you are limited to 6 slave nodes. On the master radio you will need to set the addresses of data pipes 0-5 to the slave TX addresses. The master will be listening for data on all pipes and signal an interrupt whenever data is received on any of them.

To achieve bi-directional communication with a (practically) unlimited number of slave nodes, your best bet is to use the in-built ACK PAYLOAD feature of nRF24. In addition to configuring a one-to-many network, you need to enable ACK payload on each radio node. The procedure to follow is given in the nRF24L01 data sheet. I can't recommend strongly enough how important that is to read and learn from. You will be able to send a message from the master to one slave, and get data back from that node in the same radio transmission, auto-retransmit etc included in the bargain. This way you also know which node the data are coming from - without needed to encode the identity of the slave node in the message. It's incredible what these little radios will let you achieve!