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[on:]

Hi, everyone.

I have to design a wireless system which communicate between a central device and individual devices (star network). These individual devices have only one button and communication begins when the button is pressed. These devices are battery powered and all these devices should be able to communicate only with central device and there may be more than one device activated at a time because these devices are operating by persons. Inter - device communication is not possible because I need to consider the battery life of the devices.
So I though of having Frequency hopping module for central device while the other hand-held devices are tune for different frequencies.
So could you please guide me and could I know is there any other more simple technology/method than this method.

Thanks in advance

[Reply #1 on:]

I see no requirement for frequency hopping in what you've described. You just need to set up a communication protocol between your slaves and master so that you guarantee packet delivery when collisions occur, which is to say that any time a slave sends a message it should keep retransmitting until it receives a response from the master. An XBee, for example, can do this automatically.

As to what device to recommend depends on the transmission distance and how much data is being sent. And how much money you have

[Reply #2 on:]

hi,
Thank you for replying me.

The transmission distance is around 300m and only one byte is enough to send the data from slave to master.

As I know Xbee/Zigbee uses inter device communication which will consume much power from slaves. Because I have to consider the battery life of the slave devices, I though of having this method,

"The slave send the button pressed event only when button is pressed, if the master does not reply, slave waits until the button is pressed again and transmite the number of button presses (one byte length)".

I was thinking about frequency hopping because of,
If I use same frequency for all slaves with addressing; and a slave(slave-B) tries to initiate the communication with master while another slave(slave-A) is communicating will lead to loose the data form master. The both slave can know that they lost the communication and can try to send data again,
But there are more than 200 slaves 

The attachment will describe the network

thank you.

[Reply #3 on:]

Hi everyone,
After lot of search through the internet I finally came with up this, RFD21733.

RFD21733 is going to use for slave device and RFDANT is going to be used as the master. Does anyone has any experience with these modules could you please give me a feedback.

I choosed these modules because,
low power
no coding
no need to worry about collisions

Thank you.

[Reply #4 on:]

Hi everyone,

Please help me about this modules. Does any one has any experience with this, kindly reply me.

Does this module can capture simultaneous button presses of around 20 RFD21733 modules?

Am I posting this on wrong topic???

Thanks in advance.