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.
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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