File content as of revision 1:7b595c4ff156:

#include "mbed.h"
#include "spektRx.h"

#define NUM_CHAN (7)
#define NUM_BYTES_IN_FRAME (2*NUM_CHAN+2)

void spektRx_init(spektRx_t* self){
    self -> state = 0;
    self -> valid = false;
    self -> frameNum = 0L;
}

bool spektRx_hasValidFrame(spektRx_t* self){
    return self->valid;
}

void spektRx_runChar(spektRx_t* self, unsigned char c){
    switch(self->state){
        case 0: /* new frame cycle */
            /* first preamble byte received: now expect 2nd preamble byte */
            self->state = (c == 0x03) ? 1 : 0;
            break;

        case 1:
            /* 2nd preamble byte received: Now expect first data byte */             
            self->state = (c == 0x01) ? 2 : 0;
            break;

        default:
            /* store received byte */
            self->data[self -> state - 2] = c;
            ++self->state;

            if (self->state == NUM_BYTES_IN_FRAME){
                /* one complete frame was received.
                 * - Copy the data
                 * - mask out bits 10..15
                 */
                int ix; 
                for (ix = 0; ix < NUM_CHAN; ++ix){
                    self->out[ix] = ((self->data[2*ix] & 3) << 8) | self->data[2*ix+1];
                }

                /* output data is now valid */
                self->valid = true;
                ++self->frameNum;

                /* ready for the next frame */
                self->state = 0;
            } /* if frame complete */
    } /* switch state */
}

void spektRx_runSerial(spektRx_t* self, Serial* s){
    while(s -> readable())
        spektRx_runChar(self, s -> getc());
}

unsigned short* spektRx_getChannelData(spektRx_t* self){
    return (unsigned short*) self -> out;
}

float spektRx_getChannelValue(spektRx_t* self, char ixChan){
    return (float)self->out[ixChan] / 512.0f - 1.0f;
}

long spektRx_getFrameNum(spektRx_t* self){
    return self->frameNum;
}

void spektRx_invalidateFrame(spektRx_t* self){
    self->valid = false;
}