wireless

guydb

hi,
I will soon tackle a project which requires wireless communication between the Stamp and the computer. I am not sure whether to go for RF or bluetooth. especially as several stamps will have to communicate, each autonomously with the PC. any suggestions are welcome.
thanks,
Guy

Chris Savage

One thing to bear in mind is that with the BlueTooth Modules you will be able to specify a target device to speak with.· This would be difficult at best with other methods.· On the other hand you can only talk to one device at a time.· That is, two units can communicate with each other, but not any others until a new connection is established (The original is discontinued).

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Chris Savage
Parallax Tech Support
csavage@parallax.com

guydb

thanks, so on the other hand RF communication will allow me to communicate simultaneously with different devices. but I assume for this I need transceivers operating on different wavelengths (can the wavelengths be change on the transceiver Parallax sells?

Chris Savage

The problem with standard RF modules is that if multiple units are trying to talk at the same time, some information will most likely be lost.· This is because a given module will only be able to receive one signal at a time.· There are all kinds of issues that the Bluetooth Modules do overcome in that respect.


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Chris Savage
Parallax Tech Support
csavage@parallax.com

Steve Joblin

A few of us are just starting to explore a very inexpensive RF transmitter and receiver. You can buy it at Reynolds Electronics (http://www.rentron.com/rf_remote_control.htm) in the US or from Qkits in Canada. Both the Transmitter and Reciever are less that a $15 combined! At that price, you can play around with several different strategies. One idea is to transmit what you want to everyone, but only have a specific device designed to take action to that specific transmission.

Steel

At this point, it really does depend on what is most important to you.· If you have LOTS of money to develop a bluetooth module (or buy one from Parallax) for each device...hey, go for it.

It can still be done without bluetooth, though...and without separate frequencies...There·will be lost packets, but even bluetooth loses packets.· (they·do have a more robust solution)

If you have 1 host and multiple devices, you can create a protocol to communicate.· You would have the host send out a 'broadcast' packet with the First Byte being a device 'address'.

In the firmware of the device, you just simply put a 'Wait(address)' in the Serin command.· That way all devices are 'idle' until a packet with their address is recieved.

The more robust of a communication protocol you can develop, the better.· That is all that Bluetooth is selling...is a communication protocol.

...Again, it is really up to you as to which road you want to take...Bluetooth modules are quite pricey, or you can utilize your own Tx Rx method which will be much cheaper, but not as effective.

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Descention

Steve said...
A few of us are just starting to explore a very inexpensive RF transmitter and receiver. You can buy it at Reynolds Electronics (http://www.rentron.com/rf_remote_control.htm) in the US or from Qkits in Canada. Both the Transmitter and Reciever are less that a $15 combined! At that price, you can play around with several different strategies. One idea is to transmit what you want to everyone, but only have a specific device designed to take action to that specific transmission.

has anyone used these?