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Messages are 20 bits wide, with 4 bits being address bits and 16 bits being data bits. Address mapping is as follows:
| Address | Input Behavior | Output Behavior |
|---|---|---|
| 0 | Input XBar SPI inject | Input XBar SPI out |
| 1 | Input XBar config | N/A |
| 2 | Classifier XBar Inject | Classifier XBar out |
| 3 | Classifier XBar config | N/A |
| 4 | Output XBar inject | Output XBar SPI out |
| 5 | Output XBar config | N/A |
| 6 | Classifier set cutoff frequency | N/A |
| 7 | Classifier set cutoff magnitude | N/A |
| 8 | Classifier set sampling frequency | N/A |
Behavior
- Inject messages into any crossbar inject the data payload into the crossbar. This will be ignored unless the crossbar is configured properly to read SPI
- XBar config messages will read only the low 4 bits of the payload, 0xaabb. The aa bits refer to the index of the input to select (0-2) and the bb bits are the index of the output to select (0-2).
- Index 0 is always SPI
- Index 1 is always Wishbone
- Index 2 is the normal behavior (IE sending from crossbar to FFT) if it exists.
- Classifier configuration messages configure the classifier.
- Cutoff frequency sets the cutoff frequency for the classifier. Bins with frequencies in the range of [0, cutoff] are not considered in the highpass
- Cutoff magnitude is the audio amplitude magnitude at which the classifier will begin classifying.
- Sampling frequency refers to the number of samples per second that audio is coming in. This is needed to calculate the frequency of the bins of the classifier.