Wireless data transfer with these cheap modules from Velleman or QualityKits. This first prototype uses two breadboards. One sending and one receiving. My aim was to achieve a protocol with which transmitting and receiving data is pretty much reliable. The future setup will have full two-way communication with CRC and adjusting baud rates if needed.
One sending circuit which transmits the current time (from an i²c real time clock.) It sends 20 bytes in 50 to 70 mS. See waveforms below. One receiving circuit. Displays the current time received from transmitter. Around 2 readings are made per second.
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Range of this setup is around 30 meters indoors and 200 meters outdoors.
This graph how the received signal looks like. “0” is on top of the curve; “1” is at the bottom. The sample is 5mS long. The first signal going high is “transmission start” followed by “new byte” then 8 data bits (=first ID byte with value 0xaa) and then again a “new byte”. Oscilloscope 2.51 takes the LINE IN from a soundcard as a 2-channel input.
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