fpga_fan_controller [2016/08/25 20:07] joel [iCE40 FPGA Implementation] |
fpga_fan_controller [2017/12/06 11:18] |
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- | ====== FPGA Fan Controller ====== | ||
- | My Ceiling fan is controlled by a [[https:// | ||
- | {{: | ||
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- | Internally the device uses a [[http:// | ||
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- | It has a 4-bit DIP switch that controls the id of the fan that will be controlled. | ||
- | ===== Capture ===== | ||
- | ==== Gqrx ==== | ||
- | {{: | ||
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- | I used my RTLSDR and [[http:// | ||
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- | * When buttons are pressed, bunches of packets are transmitted in [[https:// | ||
- | * The carrier frequency is not at all accurately tuned to 350MHz, and drifts significantly based on the transmitter' | ||
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- | ==== Inspectrum ==== | ||
- | {{: | ||
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- | [[https:// | ||
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- | Analysis of the transmissions captured by Gqrx revealed that the packets are sent in a PWM (pulse-width modulation) scheme over OOK. | ||
- | ==== GNU Radio ==== | ||
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- | With the modulation of the packets now known, I used GNU radio to construct a real-time version of the Inspectrum demodulator. | ||
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- | ==== Packet Format ==== | ||
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- | ^ Command | ||
- | ^ Off | 0 | 0 | LSB | ⋅ | ⋅ | MSB | 1 | 1 | 1 | 1 | 0 | 0 | 1 | | ||
- | ^ Speed 1 | ::: | ::: | ::: | ::: | ::: | ::: | 1 | 1 | 1 | 0 | 0 | 0 | 1 | | ||
- | ^ Speed 2 | ::: | ::: | ::: | ::: | ::: | ::: | 1 | 1 | 1 | 0 | 0 | 1 | 0 | | ||
- | ^ Speed 3 | ::: | ::: | ::: | ::: | ::: | ::: | 1 | 1 | 1 | 0 | 1 | 0 | 0 | | ||
- | ^ Lamp On/Off | ::: | ::: | ::: | ::: | ::: | ::: | 1 | 1 | 1 | 1 | 0 | 0 | 0 | | ||
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- | {{: | ||
- | ===== iCE40 FPGA Implementation ===== | ||
- | I wanted to make use of the [[http:// | ||
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- | Because of the simple modulation scheme, it's possible to transmit the 350MHz packets by simply wiggling a pin with a flying lead attached, which acts as a monopole antenna. | ||
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- | The source is available on [[https:// | ||
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- | ==== Performance ==== | ||
- | The ideal quarter-wave antenna length for a monopole 350MHz is ~214mm. With a flying lead of this length, I found that the FPGA could transmit to a distance of 150m. This range is quite excessive, so I trimmed the antenna to ~50mm which the reduced the transmission distance a more reasonable distance. | ||
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- | Given that there are only 16 id-codes possible with the 4-bit DIP switch, and that the transmit range is so long, and that the fans in my housing complex are presumably all the same type, it would be easy to prank the neighbors in the housing complex by transmitting random commands to all the ids at once. |