Spasm said:
Thank you masta Chippie for the info..Yeah..thats actually what i wanted to do..data transmission.
But Chippie..does the Tx/Rx u had mentioned has a DAC/ADC converter all build in? How bout for other Tx/Rx? Can I just put the output digital signal straight into the input for the Tx??
By the way do you know anyone that had already done a similar project like this?
I can't seem to find any...
Thanx
Hi Spasm,
This is not a difficult operation, but as a radio link can only carry one bit at any time, you will have to send the data serially. The idea is that the 8 bits that make up the contents of a register are shifted out, one bit at a time, onto one of the port o/p pins of the micro (uC1) and sent to the transmitter.
If you have more than 1 register to send then you need some way of identifying the beginning and end of each byte. The accepted way of doing that is to have the o/p pin normally sitting low ie. a 0. When you send the byte you add a start bit before the data. This means you take the pin high (1) for one bit period, then send the 8 bits and follow them by at least one bit period at 0 as a stop bit. That is the standard protocol when communicating with a computer, but for uC to uC, you dont have to stick with that, ie. You can send words 16 bits long if you like.
At the micro that is being used to receive the signal (uC2), the radio receiver would feed into an input pin that is constantly watched for incoming data. If the sole purpose of uC2 was to look for data and act on it, then OK. But the chances are it will be doing other things as well. The answer then would be to arrange in the software for the input pin to cause an interrupt whenever data arrived. The uC could then interrupt whatever task it was doing at the time to service the interrupt and read in the data. You can write subroutines to read or write out the data serially.
You can see that the data would be a stream of noughts and ones. The radio tx and rx would depend on how far you want to transmit, cost, and reliability.
For short distances you can pick a simple AM transmitter. There is one type that is just a blob with 2 connections. You put volts on to it and it transmits; take the volts off and it stops! You cannot get mush simpler than that for a simple on/off digital signal. The receiver is a simple AM one.
For longer distances where interference may be a problem you would be advised to go for FM, but the costs are a bit more. No doubt there are others who could advise you better.
I hope thats not too longwinded