Add some band utility functions for later use

bands.cpp

@@ -0,0 +1,116 @@
+#include <avr/pgmspace.h>
+
+#include "bands.h"
+#include "utils.h"
+
+/*
+ * These are the bands for USA. Your bands may vary
+ */
+struct Band_t {
+  uint32_t min;
+  uint32_t max;
+  uint8_t band_meters;
+  const char name[3];//Two characters + null terminator. Fixed width so we don't need to build separate pointers
+};
+
+const char UNKNOWN_BAND_NAME [] PROGMEM = "??";
+
+constexpr Band_t bands [] PROGMEM {
+  {       0UL,      255UL, 255, "U8"},//Utility conversion option
+  {       0UL,    65535UL, 254, "UF"},//Utility conversion option
+  {  530000UL,  1700000UL, 253, "AM"},//Broadcast AM, actually centers at 268, but uint8 can't do that
+  { 1800000UL,  2000000UL, 160, "A0"},//0xA0 is 160
+  { 3500000UL,  4000000UL,  80, "80"},
+  { 5330500UL,  5403500UL,  60, "60"},
+  { 7000000UL,  7300000UL,  40, "40"},
+  {10100000UL, 10150000UL,  30, "30"},
+  {14000000UL, 14350000UL,  20, "20"},
+  {18068000UL, 18168000UL,  17, "17"},
+  {21000000UL, 21450000UL,  15, "15"},
+  {24890000UL, 24990000UL,  12, "12"},
+  {26965000UL, 27405000UL,  11, "CB"},//Citizen's Band
+  {28000000UL, 29700000UL,  10, "10"},
+};
+constexpr uint8_t NUM_BANDS = sizeof(bands)/sizeof(bands[0]);
+
+int8_t findBandIndexFromBand(const uint8_t band)
+{
+  for(uint8_t i = 0; i < NUM_BANDS; ++i){
+    if(band == bands[i].band_meters){
+      return i;
+    }
+  }
+
+  return -1;
+}
+
+int8_t findBandIndexFromFreq(uint32_t frequency)
+{
+  for(uint8_t i = 0; i < NUM_BANDS; ++i){
+    if(frequency <= bands[i].max){
+      if(bands[i].min <= frequency){
+        return i;
+      }
+      //No bands overlap, and they are ordered in strictly increasing frequency, so we need search no further
+      return -1;
+    }
+  }
+
+  return -1;
+}
+
+void getBandString(const unsigned long frequency,
+                   char* band_string_out,
+                   uint16_t max_string_length)
+{
+  int8_t band_index = findBandIndexFromFreq(frequency);
+  if(-1 == band_index){
+    strncpy_P(band_string_out,UNKNOWN_BAND_NAME,max_string_length);
+  }
+  else{
+    strncpy_P(band_string_out,bands[band_index].name,max_string_length);
+  }
+}
+
+uint32_t getFreqInBand(const uint32_t frequency,
+                       const uint8_t target_band)
+{
+  int8_t target_band_index = findBandIndexFromBand(target_band);
+  if(-1 == target_band_index){
+    //Hard to target a band we don't know about...
+    return frequency;
+  }
+
+  //See if we're currrently in a valid band
+  int8_t current_band_index = findBandIndexFromFreq(frequency);
+
+  if(-1 == current_band_index){
+    //We're not in a known band - just go to the center of the target band
+    return ((bands[target_band_index].max - bands[target_band_index].min)/2/100)*100;//truncated 100Hz
+  }
+  else{
+    //We're in a known band. Match the relative position in the target band.
+    const uint32_t range_current = bands[current_band_index].max - bands[current_band_index].min;
+    const uint32_t range_target = bands[target_band_index].max - bands[target_band_index].min;
+    return (((frequency - bands[current_band_index].min) * range_target / range_current + bands[target_band_index].min)/100)*100;//truncated 100Hz
+  }
+}
+
+bool isFreqInBand(const uint32_t frequency,
+                  const uint8_t band)
+{
+  int8_t band_index = findBandIndexFromBand(band);
+
+  if(-1 == band_index){
+    //Unknown band - can't be in it
+    return false;
+  }
+
+  if( (frequency <= bands[band_index].max)
+   && (bands[band_index].min <= frequency)){
+      return true;
+  }
+
+  return false;
+}
+

bands.h

@@ -0,0 +1,11 @@
+#include <stdint.h>
+
+void getBandString(const uint32_t frequency,
+                   char* band_string_out,
+                   const uint16_t max_string_length);
+
+uint32_t getFreqInBand(const uint32_t frequency,
+                       const uint8_t target_band);
+
+bool isFreqInBand(const uint32_t frequency,
+                  const uint8_t band);