120 lines
5.1 KiB
C
120 lines
5.1 KiB
C
//////////////////////////////////////////////////////
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// First things first, all the includes we need //
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//////////////////////////////////////////////////////
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#ifndef FSK_MODEM_H
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#define FSK_MODEM_H
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#include "config.h" // Various configuration values
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#include "hardware.h" // Hardware functions
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#include <cfg/compiler.h> // Compiler info from BertOS
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#include <struct/fifobuf.h> // FIFO buffer implementation from BertOS
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#include <io/kfile.h> // The BertOS KFile interface. This is
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// used for letting other functions read
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// from or write to the modem like a
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// file descriptor.
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//////////////////////////////////////////////////////
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// Our type definitions and function declarations //
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//////////////////////////////////////////////////////
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#define SAMPLERATE 9600 // The rate at which we are sampling and synthesizing
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#define BITRATE 1200 // The actual bitrate at baseband. This is the baudrate.
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#define SAMPLESPERBIT (SAMPLERATE / BITRATE) // How many DAC/ADC samples constitute one bit (8).
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// This defines an errortype for a receive-
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// buffer overrun.
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#define RX_OVERRUN BV(0)
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// This struct defines a Hdlc parser. It will let
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// us parse the raw bits coming in from the modem
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// and synchronise to byte boundaries.
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typedef struct Hdlc
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{
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uint8_t demodulatedBits; // Incoming bitstream from demodulator
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uint8_t bitIndex; // The current received bit in the current received byte
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uint8_t currentByte; // The byte we're currently receiving
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bool receiving; // Whether or not where actually receiving data (or just noise ;P)
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} Hdlc;
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// This is our primary modem struct. It defines
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// all the values we need to modulate and
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// demodulate data from the physical medium.
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typedef struct Afsk
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{
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KFile fd; // A file descriptor for reading from and
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// writing to the modem
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// I/O hardware pins
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int adcPin; // Pin for incoming signal
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// General values
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Hdlc hdlc; // We need a link control structure
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uint16_t preambleLength; // Length of sync preamble
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uint16_t tailLength; // Length of transmission tail
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// Modulation values
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uint8_t sampleIndex; // Current sample index for outgoing bit
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uint8_t currentOutputByte; // Current byte to be modulated
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uint8_t txBit; // Mask of current modulated bit
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bool bitStuff; // Whether bitstuffing is allowed
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uint8_t bitstuffCount; // Counter for bit-stuffing
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uint16_t phaseAcc; // Phase accumulator
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uint16_t phaseInc; // Phase increment per sample
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FIFOBuffer txFifo; // FIFO for transmit data
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uint8_t txBuf[CONFIG_AFSK_TX_BUFLEN]; // Actial data storage for said FIFO
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volatile bool sending; // Set when modem is sending
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// Demodulation values
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FIFOBuffer delayFifo; // Delayed FIFO for frequency discrimination
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int8_t delayBuf[SAMPLESPERBIT / 2 + 1]; // Actual data storage for said FIFO
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FIFOBuffer rxFifo; // FIFO for received data
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uint8_t rxBuf[CONFIG_AFSK_RX_BUFLEN]; // Actual data storage for said FIFO
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int16_t iirX[2]; // IIR Filter X cells
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int16_t iirY[2]; // IIR Filter Y cells
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uint8_t sampledBits; // Bits sampled by the demodulator (at ADC speed)
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int8_t currentPhase; // Current phase of the demodulator
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uint8_t actualBits; // Actual found bits at correct bitrate
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volatile int status; // Status of the modem, 0 means OK
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} Afsk;
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// Explanation nessecary for this. BertOS uses an
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// object-oriented approach for handling "file-like"
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// transactions (yes, we are using C :P). What we are
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// doing here is defining a specific "file type" for
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// the standard KFile to identify the modem as a "file"
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// that can be read from and written to.
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#define KFT_AFSK MAKE_ID('F', 'S', 'K', 'M')
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// We then make a macro that can "typecast" a generic
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// KFile file-pointer to an Afsk "object". This lets
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// other pieces of code read from and write to the AFSK
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// "objects" buffers with the standard KFile operations.
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// If this seems weird and confusing, check out the
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// BertOS KFile explanation at:
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// http://www.bertos.org/use/tutorial-front-page/drivers-kfile-interface
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INLINE Afsk *AFSK_CAST(KFile *fd) {
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// We need to assert that the what we are trying
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// to read/write is actually an AFSK "object",
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// identified by the KFT_AFSK constant
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ASSERT(fd->_type == KFT_AFSK);
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return (Afsk *)fd;
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}
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// Declare Interrupt Service Routines
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// and initialization functions
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void afsk_adc_isr(Afsk *af, int8_t sample);
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uint8_t afsk_dac_isr(Afsk *af);
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void afsk_init(Afsk *af, int adc_ch);
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#endif |