Sending Data Over Wireless Modules

Five years ago, sending data back from remote systems has always been a pain and required a good bit of engineering knowledge.  Fortunately, we can buy a set of wireless transmitter and receiver modules for $2.  A few details about these modules:

• They operate at 433MHz
• Data rates (baud) should be kept to 4800bps or lower (quality starts to diminish above 4000bps)
• The transmitter can be powered with up to 12V, for greater range
• Range is greatly increased by adding a 17cm antenna (straight piece of wire) to each module
• The receiver will pickup a LOT of noise, so expect good and LOTS of bad data
• Debugging data from the receiver is greatly simplified with a basic logic analyzer for $12
• The receiver relies on the transmitter sending a preamble burst of data, so that it can lock onto the strong signal (vs background noise).  I recommend sending about 30 characters of 0xF0 before sending real data
• Best practice is to utilize Manchester encoding for the data (I did not)
• IT WILL BE NOISY. Be prepared to write code sift and sort out noise from data
• ATAD == data input.  For the life of me, I cannot find out what this stand for.

A quick tip for starting out is to not even worry about the, "Odd" baud rate of 4000 and just start out with a standard UART rate of 4800bps.  One reason is that for debugging purposes, you can tap the RX port of a USB->TTL adapter to the ATAD pin and monitor the data going over the air.