+ /** Base "class" */
+ KFile fd;
+
+ /** ADC channel to be used by the demodulator */
+ int adc_ch;
+
+ /** DAC channel to be used by the modulator */
+ int dac_ch;
+
+ /** Current sample of bit for output data. */
+ uint8_t sample_count;
+
+ /** Current character to be modulated */
+ uint8_t curr_out;
+
+ /** Mask of current modulated bit */
+ uint8_t tx_bit;
+
+ /** True if bit stuff is allowed, false otherwise */
+ bool bit_stuff;
+
+ /** Counter for bit stuffing */
+ uint8_t stuff_cnt;
+ /**
+ * DDS phase accumulator for generating modulated data.
+ */
+ uint16_t phase_acc;
+
+ /** Current phase increment for current modulated bit */
+ uint16_t phase_inc;
+
+ /** Delay line used to delay samples by (SAMPLEPERBIT / 2) */
+ FIFOBuffer delay_fifo;
+
+ /**
+ * Buffer for delay FIFO.
+ * The 1 is added because the FIFO macros need
+ * 1 byte more to handle a buffer (SAMPLEPERBIT / 2) bytes long.
+ */
+ int8_t delay_buf[SAMPLEPERBIT / 2 + 1];
+
+ /** FIFO for received data */
+ FIFOBuffer rx_fifo;
+
+ /** FIFO rx buffer */
+ uint8_t rx_buf[CONFIG_AFSK_RX_BUFLEN];
+
+ /** FIFO for transmitted data */
+ FIFOBuffer tx_fifo;
+
+ /** FIFO tx buffer */
+ uint8_t tx_buf[CONFIG_AFSK_TX_BUFLEN];
+
+ /** IIR filter X cells, used to filter sampled data by the demodulator */
+ int16_t iir_x[2];
+
+ /** IIR filter Y cells, used to filter sampled data by the demodulator */
+ int16_t iir_y[2];
+
+ /**
+ * Bits sampled by the demodulator are here.
+ * Since ADC samplerate is higher than the bitrate, the bits here are
+ * SAMPLEPERBIT times the bitrate.
+ */
+ uint8_t sampled_bits;
+
+ /**
+ * Current phase, needed to know when the bitstream at ADC speed
+ * should be sampled.
+ */
+ int8_t curr_phase;
+
+ /** Bits found by the demodulator at the correct bitrate speed. */
+ uint8_t found_bits;
+
+ /** True while modem sends data */
+ volatile bool sending;
+
+ /**
+ * AFSK modem status.
+ * If 0 all is ok, otherwise errors are present.
+ */
+ volatile int status;
+
+ /** Hdlc context */
+ Hdlc hdlc;
+
+ /**
+ * Preamble length.
+ * When the AFSK modem wants to send data, before sending the actual data,
+ * shifts out preamble_len HDLC_FLAG characters.
+ * This helps to synchronize the demodulator filters on the receiver side.
+ */
+ uint16_t preamble_len;
+
+ /**
+ * Trailer length.
+ * After sending the actual data, the AFSK shifts out
+ * trailer_len HDLC_FLAG characters.
+ * This helps to synchronize the demodulator filters on the receiver side.
+ */
+ uint16_t trailer_len;