goodwatch/firmware/apps/counter.c

/*! \file counter.c
  \brief Frequency Counter Application

  Howdy y'all,
  
  Once upon a time, a neighbor was in Heidelberg for the Troopers
  conference, and he wanted to join the staff radio networks.  So he
  performed the out-of-band-TX mod to his Kenwood TH-D74, and borrowed
  a laptop and SDR to find the staff simplex frequency.  From an audio
  recording, he identified the squelch tones and was on the air.
  
  But why did he need an SDR, when his wristwatch ought to have been
  able to quickly find the peak during transmission?  This applet
  seeks to remedy that problem by providing a basic frequency counter,
  displaying the center frequency of the strongest signal yet
  observed.  It is loosely based on Michael Ossmann's spectrum
  analyzer, written for the Girltech IMME in 2010.

  This implementation does a wideband sweep from 410 to 470
  MHz when the 0 button is pressed.  The 1 button repeats the broad
  sweep without forgetting the old peak.

  Generally, you will just run these all by pressing 0, but for TDMA
  protocols like DMR/MotoTrbo, it's handy to rerun the scan by
  starting with the 1 button.
  
  The result will be off by up to 100kHz, so just treat the result as
  a decent guess.  Later versions will scan other bands.
  
  Press '=' to copy the frequency to the VLO.
  
  --Travis
  
*/

#include<stdio.h>
#include<string.h>
#include<msp430.h>
#include "api.h"


/* Settings were prototyped first in Python.  This is basic OOK with
   no preamble, no CRC, and 341µs symbol times.
 */
#define LEN 16
static const uint8_t counter_settings[]={
  /* IF of 457.031 kHz */
  FSCTRL1, 0x12,
  FSCTRL0, 0x00,
  
  /* disable 3 highest DVGA settings */
  //AGCCTRL2 |= AGCCTRL2_MAX_DVGA_GAIN;
  
  /* frequency synthesizer calibration */
  FSCAL3, 0xEA,
  FSCAL2, 0x2A,
  FSCAL1, 0x00,
  FSCAL0, 0x1F,
  
  /* "various test settings" */
  TEST2, 0x88,
  TEST1, 0x31,
  TEST0, 0x09,
  
  /* no automatic frequency calibration */
  MCSM0, 0,


  /* Filter bandwidth.  270kHz seems to work best,
     even though it could be narrower. */
  //MDMCFG4, 0xFC, /* 58.0357 kHz */
  //MDMCFG4, 0xEC, /* 67.708333 kHz */
  MDMCFG4, 0x6C, /* 270.833333 kHz */
  //MDMCFG4, 0x0C, /* 812.5 kHz */

  //End with null terminator.
  0,0
};


/* This enum manages the state machine for the frequency counter.  The
   state will be IDLE before and after the sweep.
 */
static enum {IDLE, SWEEP} counter_state;
static int best_rssi;
static float best_freq;
#define MAX_BIGFREQ  470000000.0  //Range is 410 to 470 for now.
#define MIN_BIGFREQ  410000000.0  //Will open more bands later.
#define BIGSTEP_FREQ    100000.0  //100kHz/Step
static float current_freq;

//! Try a given frequency, and update display if it's best.
static void try_freq(float freq){
  int rssi;
  
  //Set the frequency.
  radio_setfreq(freq);
  
  //Get the RSSI.
  rssi=radio_getrssi();

  //Compare it.
  if(rssi>best_rssi){
    best_rssi=rssi;
    best_freq=freq;
  }

}



//! Try the next frequency in the wide set.
static void try_nextbig(){
  //Enforce the range here.
  if(current_freq<MIN_BIGFREQ)
    current_freq=MIN_BIGFREQ;

  //Try the next center freq and step ahead.
  try_freq(current_freq);
  current_freq+=BIGSTEP_FREQ;

  //We're done!
  if(current_freq>MAX_BIGFREQ){
    current_freq=MIN_BIGFREQ;
    counter_state=IDLE;
  }
}

//! Enter the Counter application.
void counter_init(){
  /* This enters the application.
     We ignore the codeplug frequency and set our own.
   */
  if(has_radio){
    //Faster processing time, for rapid packet succession.
    ucs_fast();
    
    radio_on();
    radio_writesettings(counter_settings);

    //Initialize state variables.
    counter_state=IDLE;
    best_rssi=0;
    best_freq=0;
  }else{
    app_next();
  }
}

//! Exit the Counter application.
int counter_exit(){
  //Cut the radio off and drop the CPU frequency.
  radio_off();
  ucs_slow();
  
  //Allow the exit.
  return 0;
}

//! Draw the counter's status.
static void counter_drawstatus(){
  lcd_number(current_freq/10);
}

//! Draw the Counter screen.
void counter_draw(){
  switch(counter_state){
  case IDLE:
    if(best_rssi==0)
      lcd_string("CNT IDLE");
    else
      lcd_number(best_freq/10);
    break;
  case SWEEP:
    //lcd_string("SWEEPING");
    break;
  }
}

//! Keypress handler for the Counter applet.
int counter_keypress(char ch){
  int i=0;


  /* No break statements because the stages run in order.
   */
  switch(ch){
  case '0': //Begin a new broad sweep.
    best_rssi=0;
    
  case '1': //Second pass of the broad sweep sweep.
    counter_state=SWEEP;
    current_freq = MIN_BIGFREQ;
    
    //Do the sweep.
    while(counter_state==SWEEP){
      try_nextbig();
      //Draw every 64th channel.
      if((i++&0x3f)==0)
	counter_drawstatus();
    }

    break;

  case '=': //Copy best freq to VFO.
    codeplug_setvfofreq(best_freq);
    break;
  }
  return 0;
}