OpenModem/Modem/afsk.h

#ifndef FSK_MODEM_H
#define FSK_MODEM_H

#include "config.h"
#include "hardware.h"

#include <cfg/compiler.h>
#include <io/kfile.h>
#include <struct/fifobuf.h>


#define SAMPLERATE 9600
#define BITRATE    1200
#define SAMPLESPERBIT (SAMPLERATE / BITRATE)

typedef struct Hdlc
{
	uint8_t demodulatedBits;  	// Incoming bitstream from demodulator
	uint8_t bitIndex;			// The current received bit in the current received byte
	uint8_t currentByte;		// The byte we're currently receiving
	bool receiving;				// Whether or not where actually receiving data (or just noise ;P)
} Hdlc;

#define RX_OVERRUN BV(0)

typedef struct Afsk
{
	KFile fd;

	// I/O hardware pins
	int adcPin;								// Pin for incoming signal
	int dacPin;								// Pin for outgoing signal

	// General values
	Hdlc hdlc; 								// We need a link control structure
	uint16_t preambleLength;				// Length of sync preamble
	uint16_t tailLength;					// Length of transmission tail

	// Modulation values
	uint8_t sampleIndex;					// Current sample index for outgoing bit 
	uint8_t currentOutputByte;				// Current byte to be modulated
	uint8_t txBit;							// Mask of current modulated bit
	bool bitStuff;							// Whether bitstuffing is allowed

	uint8_t bitstuffCount;					// Counter for bit-stuffing

	uint16_t phaseAcc;						// Phase accumulator
	uint16_t phaseInc;						// Phase increment per sample

	FIFOBuffer txFifo;						// FIFO for transmit data
	uint8_t txBuf[CONFIG_AFSK_TX_BUFLEN];	// Actial data storage for said FIFO

	volatile bool sending;					// Set when modem is sending

	// Demodulation values
	FIFOBuffer delayFifo;					// Delayed FIFO for frequency discrimination
	int8_t delayBuf[SAMPLESPERBIT / 2 + 1];// Actual data storage for said FIFO

	FIFOBuffer rxFifo;						// FIFO for received data
	uint8_t rxBuf[CONFIG_AFSK_RX_BUFLEN];	// Actual data storage for said FIFO

	int16_t iirX[2];						// IIR Filter X cells
	int16_t iirY[2];						// IIR Filter Y cells

	uint8_t sampledBits;					// Bits sampled by the demodulator (at ADC speed)
	int8_t currentPhase;					// Current phase of the demodulator
	uint8_t actualBits;						// Actual found bits at correct bitrate

	volatile int status;					// Status of the modem, 0 means OK

} Afsk;

#define KFT_AFSK MAKE_ID('F', 'S', 'K', 'M')

INLINE Afsk *AFSK_CAST(KFile *fd)
{
  ASSERT(fd->_type == KFT_AFSK);
  return (Afsk *)fd;
}


void afsk_adc_isr(Afsk *af, int8_t sample);
uint8_t afsk_dac_isr(Afsk *af);
void afsk_init(Afsk *af, int adc_ch, int dac_ch);

int afsk_testSetup(void);
int afsk_testRun(void);
int afsk_testTearDown(void);

#endif