Software
Strictly speaking, there’s no software required to run the project. You simply take a working serial link running at 2.4 Kbps or less and insert the radios into the link. Nevertheless, software is essential for integration and test of the project so you can incrementally build and test under known conditions.We integrated the transmitter and receiver for one frequency at a time, verifying first at low rate and range and then extending to maximum frequency and testing for range.
We used a Javelin Stamp to support those tests, verifying initial link operation with the loopback circuit.
The code outputs a stream of ‘-’ characters to the console if loopback works, ‘|’ characters if an incorrect character is received, and ‘X’ characters if no character is received after a sufficient delay.We increment the character being sent and received to ensure that only live data is accepted, not any stale data that might be in the buffer if an error occurs, and only output when the transmit buffer is empty.
Once you prove out basic half duplex operation, try strings of characters at full speed, with buffering, and then advance to a full duplex pair of paths. If everything’s working properly, you should be able to transmit virtually limitless numbers of characters at close range with no errors. (You could put error counters in the code to monitor performance, because you don’t want to sit there watching for an error indication that should never come.)