Garmin GPS 25 LP Technical Specification page 41

dle and etx bytes:
Software written to receive the two records should filter dle and etx bytes as described below:
typedef enum
{
dat,
dle,
etx
} rx_state_type;
char in_que[256];
int in_que_ptr = 0;
rx_state_type rx_state = dat;
void add_to_que( char data )
{
#define dle_byte 0x10
#define etx_byte 0x03
if (rx_state == dat)
{
if (data == dle_byte)
{
rx_state = dle;
}
else
{
in_que[ in_que_ptr++ ] = data;
}
}
else if (rx_state == dle)
{
if (data == etx_byte)
{
rx_state = etx;
}
else
{
rx_state = dat;
in_que[ in_que_ptr++ ] = data;
}
}
else if (rx_state == etx)
{
if (data == dle_byte)
{
rx_state = dle;
}
}
if (in_que_ptr > 255)
{
in_que_ptr = 0;
}
}
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