autoseek.c

美国模拟混合器件领导厂商Silabs 芯科实验室 收音机系列 源码

//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------
#include <c8051f320.h>        
#include <stddef.h>       
#include "typedefs.h"
#include "example.h"

//-----------------------------------------------------------------------------
// Defines
//-----------------------------------------------------------------------------


//-----------------------------------------------------------------------------
// Global variables
//-----------------------------------------------------------------------------
u16 seek_preset[NUM_SEEK_PRESETS];

//-----------------------------------------------------------------------------
// Function prototypes
//-----------------------------------------------------------------------------
void si470x_tune (u16 frequency);
u8 si470x_seek (u8 seekup);
u16 si470x_get_frequency(void);
u8 si470x_get_rssi(void);
void _nop_(void);

//-----------------------------------------------------------------------------
// Inserts a channel in the preset array. First it finds the channel with the 
// lowest rssi.  If the current channel has a higher rssi, the channel with the
// lowest rssi is replaced. Channels are kept in order of increasing frequency.
//
// Inputs:
//		frequency:  		Frequency of station found
//		rssi:				Rssi of station found
//		seek_prset_rssi:	Array of rsssi values for each preset
// 
//-----------------------------------------------------------------------------
static void insert_preset(u16 frequency, u8 rssi, u8 *seek_preset_rssi)
{
	u8 i;
	u8 min_rssi = 0xff;
	u8 min_rssi_preset=0;
		   
	// first find the minimum rssi and its location
	// this will always stop at the first location with a zero rssi
	for (i=0; i<NUM_SEEK_PRESETS; i++) {
		if (seek_preset_rssi[i] < min_rssi) {
			min_rssi = seek_preset_rssi[i];
			min_rssi_preset = i;
		}
	}

	// return if current preset rssi is less than minimum preset in array
	if (rssi < min_rssi)
		return;
	   
	// delete the preset with the minimum rssi, and clear the last preset
	// since it would only be a copy of the second to last preset after
	// the deletion
	for (i=min_rssi_preset; i<NUM_SEEK_PRESETS-1; i++) {
		seek_preset[i] = seek_preset[i+1];
		seek_preset_rssi[i] = seek_preset_rssi[i+1];
	}	
	seek_preset[i] = 0;
	seek_preset_rssi[i] = 0;

	// fill the first preset with a zero for the frequency.  This will
	// always overwrite the last preset once all presets have been filled.
	for (i=min_rssi_preset; i<NUM_SEEK_PRESETS; i++) {
		if(seek_preset[i] == 0) {
			seek_preset[i] = frequency;
			seek_preset_rssi[i] = rssi;
			break;
		}
	}		  
}	
	
//-----------------------------------------------------------------------------
// This routine scans the band and populates the seek_presets array with the
// strongest signals in the band.  If the band is searched without filling all
// presets, the lowest preset numbers are left set to zero.  Do not tune to
// presets set to zero.
//
// Note that during autoseek, the seek threshold can be lowered to increase 
// the chances of filling all of the presets.  A lower seek threshold will 
// only increase the seek time and fill empty preset slots with weak stations
// instead of leaving them set to zero.  It should not change the outcome in
// the preset array.
// 
//-----------------------------------------------------------------------------
void si470x_autoseek(void)
{
	u8 seek_preset_rssi	[NUM_SEEK_PRESETS];  // local array storing rssi of each preset.
	u8 i;
	u8 seek_fail;
	u16 current_frequency, last_frequency;

	// initialize preset array and rssi array
	for (i=0; i<NUM_SEEK_PRESETS; i++) {
		seek_preset_rssi[i] = 0;
		seek_preset[i] = 0;
	}

	// tune to the bottom of the band, then seek up once
	si470x_tune(0);
	last_frequency = si470x_get_frequency();                           	 
	seek_fail = si470x_seek(1); 	   
	current_frequency = si470x_get_frequency();                           	 

	while ((seek_fail == 0) && (last_frequency < current_frequency)) {
		insert_preset(current_frequency, si470x_get_rssi(), seek_preset_rssi);
		
		last_frequency = current_frequency;
		seek_fail = si470x_seek(1);                 // seek up to the next station 	   
		current_frequency = si470x_get_frequency();                           	 
	} 

}