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fpga_fan_controller [2016/08/25 20:10] joel [Packet Format] |
fpga_fan_controller [2016/08/26 14:41] joel [Packet Format] |
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==== Packet Format ==== | ==== Packet Format ==== | ||
- | Data is transmitted by a 2/3rd / 1/3rd PWM scheme: | + | Data is transmitted by a 2/3rd / 1/3rd PWM scheme |
{{: | {{: | ||
- | ^ Command | + | ^ Command |
^ Off | 0 | 0 | LSB | ⋅ | ⋅ | MSB | 1 | 1 | 1 | 1 | 0 | 0 | 1 | | ^ Off | 0 | 0 | LSB | ⋅ | ⋅ | MSB | 1 | 1 | 1 | 1 | 0 | 0 | 1 | | ||
^ Speed 1 | ::: | ::: | ::: | ::: | ::: | ::: | 1 | 1 | 1 | 0 | 0 | 0 | 1 | | ^ Speed 1 | ::: | ::: | ::: | ::: | ::: | ::: | 1 | 1 | 1 | 0 | 0 | 0 | 1 | | ||
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==== Performance ==== | ==== 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 | + | 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 |
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. | 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. |