[SX126x] Use predefined image calibration bands (#1051)

src/modules/SX126x/SX1262.cpp

@@ -51,13 +51,46 @@ int16_t SX1262::setFrequency(float freq) {
   return(setFrequency(freq, true));
 }
 
-int16_t SX1262::setFrequency(float freq, bool calibrate, float band) {
+int16_t SX1262::setFrequency(float freq, bool calibrate) {
   RADIOLIB_CHECK_RANGE(freq, 150.0, 960.0, RADIOLIB_ERR_INVALID_FREQUENCY);
 
   // calibrate image rejection
   if(calibrate) {
-    int16_t state = SX126x::calibrateImage(freq - band, freq + band);
+    uint8_t data[2] = { 0, 0 };
+
+    // try to match the frequency ranges
+    int freqBand = (int)freq;
+    if((freq >= 902) && (freq <= 928)) {
+      data[0] = RADIOLIB_SX126X_CAL_IMG_902_MHZ_1;
+      data[1] = RADIOLIB_SX126X_CAL_IMG_902_MHZ_2;
+    } else if((freq >= 863) && (freq <= 870)) {
+      data[0] = RADIOLIB_SX126X_CAL_IMG_863_MHZ_1;
+      data[1] = RADIOLIB_SX126X_CAL_IMG_863_MHZ_2;
+    } else if((freq >= 779) && (freq <= 787)) {
+      data[0] = RADIOLIB_SX126X_CAL_IMG_779_MHZ_1;
+      data[1] = RADIOLIB_SX126X_CAL_IMG_779_MHZ_2;
+    } else if((freq >= 470) && (freq <= 510)) {
+      data[0] = RADIOLIB_SX126X_CAL_IMG_470_MHZ_1;
+      data[1] = RADIOLIB_SX126X_CAL_IMG_470_MHZ_2;
+    } else if((freq >= 430) && (freq <= 440)) {
+      data[0] = RADIOLIB_SX126X_CAL_IMG_430_MHZ_1;
+      data[1] = RADIOLIB_SX126X_CAL_IMG_430_MHZ_2;
+    }
+
+    int16_t state;
+    if(data[0]) {
+      // matched with predefined ranges, do the calibration
+      state = SX126x::calibrateImage(data);
+    
+    } else {
+      // if nothing matched, try custom calibration - the may or may not work
+      RADIOLIB_DEBUG_BASIC_PRINTLN("Failed to match predefined frequency range, trying custom");
+      state = SX126x::calibrateImageRejection(freq - 4.0f, freq + 4.0f);
+    
+    }
+    
     RADIOLIB_ASSERT(state);
+    
   }
 
   // set frequency

src/modules/SX126x/SX1262.h

@@ -75,12 +75,9 @@ class SX1262: public SX126x {
       \brief Sets carrier frequency. Allowed values are in range from 150.0 to 960.0 MHz.
       \param freq Carrier frequency to be set in MHz.
       \param calibrate Run image calibration.
-      \param band Half bandwidth for image calibration. For example,
-      if carrier is 434 MHz and band is set to 4 MHz, then the image will be calibrate
-      for band 430 - 438 MHz. Unused if calibrate is set to false, defaults to 4 MHz
       \returns \ref status_codes
     */
-    int16_t setFrequency(float freq, bool calibrate, float band = 4);
+    int16_t setFrequency(float freq, bool calibrate);
 
     /*!
       \brief Sets output power. Allowed values are in range from -9 to 22 dBm.

src/modules/SX126x/SX1268.cpp

@@ -52,13 +52,40 @@ int16_t SX1268::setFrequency(float freq) {
 }
 
 /// \todo integers only (all modules - frequency, data rate, bandwidth etc.)
-int16_t SX1268::setFrequency(float freq, bool calibrate, float band) {
+int16_t SX1268::setFrequency(float freq, bool calibrate) {
   RADIOLIB_CHECK_RANGE(freq, 410.0, 810.0, RADIOLIB_ERR_INVALID_FREQUENCY);
 
   // calibrate image rejection
   if(calibrate) {
-    int16_t state = SX126x::calibrateImage(freq - band, freq + band);
+    uint8_t data[2] = { 0, 0 };
+
+    // try to match the frequency ranges
+    int freqBand = (int)freq;
+    if((freq >= 779) && (freq <= 787)) {
+      data[0] = RADIOLIB_SX126X_CAL_IMG_779_MHZ_1;
+      data[1] = RADIOLIB_SX126X_CAL_IMG_779_MHZ_2;
+    } else if((freq >= 470) && (freq <= 510)) {
+      data[0] = RADIOLIB_SX126X_CAL_IMG_470_MHZ_1;
+      data[1] = RADIOLIB_SX126X_CAL_IMG_470_MHZ_2;
+    } else if((freq >= 430) && (freq <= 440)) {
+      data[0] = RADIOLIB_SX126X_CAL_IMG_430_MHZ_1;
+      data[1] = RADIOLIB_SX126X_CAL_IMG_430_MHZ_2;
+    }
+
+    int16_t state;
+    if(data[0]) {
+      // matched with predefined ranges, do the calibration
+      state = SX126x::calibrateImage(data);
+    
+    } else {
+      // if nothing matched, try custom calibration - the may or may not work
+      RADIOLIB_DEBUG_BASIC_PRINTLN("Failed to match predefined frequency range, trying custom");
+      state = SX126x::calibrateImageRejection(freq - 4.0f, freq + 4.0f);
+    
+    }
+    
     RADIOLIB_ASSERT(state);
+
   }
 
   // set frequency

src/modules/SX126x/SX1268.h

@@ -74,12 +74,9 @@ class SX1268: public SX126x {
       \brief Sets carrier frequency. Allowed values are in range from 150.0 to 960.0 MHz.
       \param freq Carrier frequency to be set in MHz.
       \param calibrate Run image calibration.
-      \param band Half bandwidth for image calibration. For example,
-      if carrier is 434 MHz and band is set to 4 MHz, then the image will be calibrate
-      for band 430 - 438 MHz. Unused if calibrate is set to false, defaults to 4 MHz
       \returns \ref status_codes
     */
-    int16_t setFrequency(float freq, bool calibrate, float band = 4);
+    int16_t setFrequency(float freq, bool calibrate);
 
     /*!
       \brief Sets output power. Allowed values are in range from -9 to 22 dBm.

src/modules/SX126x/SX126x.h

@@ -188,6 +188,18 @@
 #define RADIOLIB_SX126X_CALIBRATE_RC64K_ON                      0b00000001  //  0     0                               enabled
 #define RADIOLIB_SX126X_CALIBRATE_ALL                           0b01111111  //  6     0   calibrate all blocks
 
+//RADIOLIB_SX126X_CMD_CALIBRATE_IMAGE
+#define RADIOLIB_SX126X_CAL_IMG_430_MHZ_1                       0x6B
+#define RADIOLIB_SX126X_CAL_IMG_430_MHZ_2                       0x6F
+#define RADIOLIB_SX126X_CAL_IMG_470_MHZ_1                       0x75
+#define RADIOLIB_SX126X_CAL_IMG_470_MHZ_2                       0x81
+#define RADIOLIB_SX126X_CAL_IMG_779_MHZ_1                       0xC1
+#define RADIOLIB_SX126X_CAL_IMG_779_MHZ_2                       0xC5
+#define RADIOLIB_SX126X_CAL_IMG_863_MHZ_1                       0xD7
+#define RADIOLIB_SX126X_CAL_IMG_863_MHZ_2                       0xDB
+#define RADIOLIB_SX126X_CAL_IMG_902_MHZ_1                       0xE1
+#define RADIOLIB_SX126X_CAL_IMG_902_MHZ_2                       0xE9
+
 //RADIOLIB_SX126X_CMD_SET_PA_CONFIG
 #define RADIOLIB_SX126X_PA_CONFIG_HP_MAX                        0x07
 #define RADIOLIB_SX126X_PA_CONFIG_PA_LUT                        0x01
@@ -1102,6 +1114,15 @@ class SX126x: public PhysicalLayer {
     */
     int16_t setPaConfig(uint8_t paDutyCycle, uint8_t deviceSel, uint8_t hpMax = RADIOLIB_SX126X_PA_CONFIG_HP_MAX, uint8_t paLut = RADIOLIB_SX126X_PA_CONFIG_PA_LUT);
 
+    /*!
+      \brief Perform image rejection calibration for the specified frequency band.
+      WARNING: Use at your own risk! Setting incorrect values may lead to decreased performance
+      \param freqMin Frequency band lower bound.
+      \param freqMax Frequency band upper bound.
+      \returns \ref status_codes
+    */
+    int16_t calibrateImageRejection(float freqMin, float freqMax);
+
 #if !RADIOLIB_GODMODE && !RADIOLIB_LOW_LEVEL
   protected:
 #endif
@@ -1119,7 +1140,7 @@ class SX126x: public PhysicalLayer {
     int16_t setDioIrqParams(uint16_t irqMask, uint16_t dio1Mask, uint16_t dio2Mask = RADIOLIB_SX126X_IRQ_NONE, uint16_t dio3Mask = RADIOLIB_SX126X_IRQ_NONE);
     virtual int16_t clearIrqStatus(uint16_t clearIrqParams = RADIOLIB_SX126X_IRQ_ALL);
     int16_t setRfFrequency(uint32_t frf);
-    int16_t calibrateImage(float freqMin, float freqMax);
+    int16_t calibrateImage(uint8_t* data);
     uint8_t getPacketType();
     int16_t setTxParams(uint8_t power, uint8_t rampTime = RADIOLIB_SX126X_PA_RAMP_200U);
     int16_t setModulationParams(uint8_t sf, uint8_t bw, uint8_t cr, uint8_t ldro);