Alternative to AM and FM transmitting for data transmission

dataradioserialtransmissionuart

So, I need to communicate wirelessly between a micro-controller and my computer. I'm building a radio receiver circuit, and a radio transmitter circuit that works on FM transmission. However, I had an idea.

I'm just transmitting binary. The receiver will go into the micro-controller's UART lane. If I'm transmitting serial data, wouldn't it be easier to simply transmit a specific un-modulated frequency that represents a one, then design the circuit to accept no radio transmission as a zero?

Then the micro-controller program could simply seek out combinations of one's and zeros that it recognized as bytes?

Is there a downside to this that I'm not thinking about? Is there already a name for this kind of rf data transmission?

Best Answer

What you describe is called On-Off Keying.

It is an extreme version of Amplitude Shift Keying where the carrier is completely off for one value.

This is the technical name for what happens when morse code is sent by a radio operator.

Wikipedia has more information on the pros and cons:

OOK is more spectrally efficient than frequency-shift keying, but more sensitive to noise when using a regenerative receiver

Related Solutions

Electronic – Simple radio serial communication

For data transmission / reception, one of the less expensive options today is a pre-built module around the nRF24L01+ Transceiver IC. These modules typically offer a built-in PCB-trace antenna, 250 Kbps to 2 MBPS bandwidth before error correction, and are tried and tested.

Most important, they save you time in debugging and antenna tuning. After thousands of people have used these modules, which are built on the manufacturer's reference designs after all, most of the kinks are pretty thoroughly ironed out. Also, being able to tap the experience of many others on the internet who have used such a module, counts for a lot when trying to resolve issues.

For instance, this listing on eBay is for a mere US$2.10 with free international shipping. It uses the 2.4 GHz band, which does not need licensing for low power use in most countries.

Another alternative is this 433 MHz band transmit / receive pair of modules (just 9.6 Kbps though), in case you specifically want to stay with transmit-only and receive-only designs. US$1.99 for the pair makes it pretty attractive.

Of course, in each case, you could as well build your own module starting from the IC manufacturer's reference design, and thus learn while implementing your radio functionality.

It is unlikely that the price advantage of massive volume production can be beaten, though.

Electronic – Atmega8 USART transmitting wrong data

Most common error: You forgot the (default) Clock Div8 Fuse and your MCU runs on 1 MHz instead of 8 MHz. Try setting your COM Baudrate to 1200 Baud on the PC.

Another nitpick:

#define FOSC 8000000UL // Clock Speed
...
#define MYUBRR (((F_CPU / (BAUD * 16UL))) - 1)

Notice that you defined FOSC but then used F_CPU in your macro.

Best Answer

Related Solutions

Electronic – Simple radio serial communication

Electronic – Atmega8 USART transmitting wrong data

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