[SX126x] Calibrate image based on frequency change (#1292)

src/modules/SX126x/SX1262.cpp

@@ -1,4 +1,6 @@
 #include "SX1262.h"
+#include <math.h>
+
 #if !RADIOLIB_EXCLUDE_SX126X
 
 SX1262::SX1262(Module* mod) : SX126x(mod) {
@@ -66,49 +68,16 @@ int16_t SX1262::beginLRFHSS(float freq, uint8_t bw, uint8_t cr, bool narrowGrid,
 }
 
 int16_t SX1262::setFrequency(float freq) {
-  return(setFrequency(freq, true));
+  return(setFrequency(freq, false));
 }
 
-int16_t SX1262::setFrequency(float freq, bool calibrate) {
+int16_t SX1262::setFrequency(float freq, bool skipCalibration) {
   RADIOLIB_CHECK_RANGE(freq, 150.0, 960.0, RADIOLIB_ERR_INVALID_FREQUENCY);
 
-  // calibrate image rejection
-  if(calibrate) {
-    uint8_t data[2] = { 0, 0 };
-
-    // try to match the frequency ranges
-    int freqBand = (int)freq;
-    if((freqBand >= 902) && (freqBand <= 928)) {
-      data[0] = RADIOLIB_SX126X_CAL_IMG_902_MHZ_1;
-      data[1] = RADIOLIB_SX126X_CAL_IMG_902_MHZ_2;
-    } else if((freqBand >= 863) && (freqBand <= 870)) {
-      data[0] = RADIOLIB_SX126X_CAL_IMG_863_MHZ_1;
-      data[1] = RADIOLIB_SX126X_CAL_IMG_863_MHZ_2;
-    } else if((freqBand >= 779) && (freqBand <= 787)) {
-      data[0] = RADIOLIB_SX126X_CAL_IMG_779_MHZ_1;
-      data[1] = RADIOLIB_SX126X_CAL_IMG_779_MHZ_2;
-    } else if((freqBand >= 470) && (freqBand <= 510)) {
-      data[0] = RADIOLIB_SX126X_CAL_IMG_470_MHZ_1;
-      data[1] = RADIOLIB_SX126X_CAL_IMG_470_MHZ_2;
-    } else if((freqBand >= 430) && (freqBand <= 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);
-
-    }
-
+  // check if we need to recalibrate image
+  if(!skipCalibration && (fabsf(freq - this->freqMHz) >= RADIOLIB_SX126X_CAL_IMG_FREQ_TRIG_MHZ)) {
+    int16_t state = this->calibrateImage(freq);
     RADIOLIB_ASSERT(state);
-
   }
 
   // set frequency

src/modules/SX126x/SX1262.h

@@ -81,18 +81,22 @@ class SX1262: public SX126x {
 
     /*!
       \brief Sets carrier frequency. Allowed values are in range from 150.0 to 960.0 MHz.
+      Will automatically perform image calibration if the frequency changes by
+      more than RADIOLIB_SX126X_CAL_IMG_FREQ_TRIG MHz.
       \param freq Carrier frequency to be set in MHz.
       \returns \ref status_codes
     */
     int16_t setFrequency(float freq) override;
 
     /*!
       \brief Sets carrier frequency. Allowed values are in range from 150.0 to 960.0 MHz.
+      Will automatically perform image calibration if the frequency changes by
+      more than RADIOLIB_SX126X_CAL_IMG_FREQ_TRIG_MHZ.
       \param freq Carrier frequency to be set in MHz.
-      \param calibrate Run image calibration.
+      \param skipCalibration Skip automated image calibration.
       \returns \ref status_codes
     */
-    int16_t setFrequency(float freq, bool calibrate);
+    int16_t setFrequency(float freq, bool skipCalibration);
 
     /*!
       \brief Sets output power. Allowed values are in range from -9 to 22 dBm.

src/modules/SX126x/SX1268.cpp

@@ -1,4 +1,6 @@
 #include "SX1268.h"
+#include <math.h>
+
 #if !RADIOLIB_EXCLUDE_SX126X
 
 SX1268::SX1268(Module* mod) : SX126x(mod) {
@@ -66,44 +68,17 @@ int16_t SX1268::beginLRFHSS(float freq, uint8_t bw, uint8_t cr, bool narrowGrid,
 }
 
 int16_t SX1268::setFrequency(float freq) {
-  return(setFrequency(freq, true));
+  return(setFrequency(freq, false));
 }
 
 /// \todo integers only (all modules - frequency, data rate, bandwidth etc.)
-int16_t SX1268::setFrequency(float freq, bool calibrate) {
+int16_t SX1268::setFrequency(float freq, bool skipCalibration) {
   RADIOLIB_CHECK_RANGE(freq, 410.0, 810.0, RADIOLIB_ERR_INVALID_FREQUENCY);
 
-  // calibrate image rejection
-  if(calibrate) {
-    uint8_t data[2] = { 0, 0 };
-
-    // try to match the frequency ranges
-    int freqBand = (int)freq;
-    if((freqBand >= 779) && (freqBand <= 787)) {
-      data[0] = RADIOLIB_SX126X_CAL_IMG_779_MHZ_1;
-      data[1] = RADIOLIB_SX126X_CAL_IMG_779_MHZ_2;
-    } else if((freqBand >= 470) && (freqBand <= 510)) {
-      data[0] = RADIOLIB_SX126X_CAL_IMG_470_MHZ_1;
-      data[1] = RADIOLIB_SX126X_CAL_IMG_470_MHZ_2;
-    } else if((freqBand >= 430) && (freqBand <= 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);
-
-    }
-
+  // check if we need to recalibrate image
+  if(!skipCalibration && (fabsf(freq - this->freqMHz) >= RADIOLIB_SX126X_CAL_IMG_FREQ_TRIG_MHZ)) {
+    int16_t state = this->calibrateImage(freq);
     RADIOLIB_ASSERT(state);
-
   }
 
   // set frequency

src/modules/SX126x/SX1268.h

@@ -80,18 +80,22 @@ class SX1268: public SX126x {
 
     /*!
       \brief Sets carrier frequency. Allowed values are in range from 410.0 to 810.0 MHz.
+      Will automatically perform image calibration if the frequency changes by
+      more than RADIOLIB_SX126X_CAL_IMG_FREQ_TRIG MHz.
       \param freq Carrier frequency to be set in MHz.
       \returns \ref status_codes
     */
     int16_t setFrequency(float freq) override;
 
     /*!
       \brief Sets carrier frequency. Allowed values are in range from 150.0 to 960.0 MHz.
+      Will automatically perform image calibration if the frequency changes by
+      more than RADIOLIB_SX126X_CAL_IMG_FREQ_TRIG_MHZ.
       \param freq Carrier frequency to be set in MHz.
-      \param calibrate Run image calibration.
+      \param skipCalibration Skip automated image calibration.
       \returns \ref status_codes
     */
-    int16_t setFrequency(float freq, bool calibrate);
+    int16_t setFrequency(float freq, bool skipCalibration);
 
     /*!
       \brief Sets output power. Allowed values are in range from -9 to 22 dBm.

src/modules/SX126x/SX126x.cpp

@@ -1954,6 +1954,43 @@ int16_t SX126x::setRfFrequency(uint32_t frf) {
   return(this->mod->SPIwriteStream(RADIOLIB_SX126X_CMD_SET_RF_FREQUENCY, data, 4));
 }
 
+int16_t SX126x::calibrateImage(float freq) {
+  uint8_t data[2] = { 0, 0 };
+
+  // try to match the frequency ranges
+  int freqBand = (int)freq;
+  if((freqBand >= 902) && (freqBand <= 928)) {
+    data[0] = RADIOLIB_SX126X_CAL_IMG_902_MHZ_1;
+    data[1] = RADIOLIB_SX126X_CAL_IMG_902_MHZ_2;
+  } else if((freqBand >= 863) && (freqBand <= 870)) {
+    data[0] = RADIOLIB_SX126X_CAL_IMG_863_MHZ_1;
+    data[1] = RADIOLIB_SX126X_CAL_IMG_863_MHZ_2;
+  } else if((freqBand >= 779) && (freqBand <= 787)) {
+    data[0] = RADIOLIB_SX126X_CAL_IMG_779_MHZ_1;
+    data[1] = RADIOLIB_SX126X_CAL_IMG_779_MHZ_2;
+  } else if((freqBand >= 470) && (freqBand <= 510)) {
+    data[0] = RADIOLIB_SX126X_CAL_IMG_470_MHZ_1;
+    data[1] = RADIOLIB_SX126X_CAL_IMG_470_MHZ_2;
+  } else if((freqBand >= 430) && (freqBand <= 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);
+
+  }
+
+  return(state);
+}
+
 int16_t SX126x::calibrateImageRejection(float freqMin, float freqMax) {
   // calculate the calibration coefficients and calibrate image
   uint8_t data[] = { (uint8_t)floor((freqMin - 1.0f) / 4.0f), (uint8_t)ceil((freqMax + 1.0f) / 4.0f) };
@@ -2103,8 +2140,9 @@ int16_t SX126x::clearDeviceErrors() {
 
 int16_t SX126x::setFrequencyRaw(float freq) {
   // calculate raw value
-  this->frf = (freq * (uint32_t(1) << RADIOLIB_SX126X_DIV_EXPONENT)) / RADIOLIB_SX126X_CRYSTAL_FREQ;
-  return(setRfFrequency(this->frf));
+  this->freqMHz = freq;
+  uint32_t frf = (this->freqMHz * (uint32_t(1) << RADIOLIB_SX126X_DIV_EXPONENT)) / RADIOLIB_SX126X_CRYSTAL_FREQ;
+  return(setRfFrequency(frf));
 }
 
 int16_t SX126x::fixSensitivity() {

src/modules/SX126x/SX126x.h

@@ -201,6 +201,7 @@
 #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
+#define RADIOLIB_SX126X_CAL_IMG_FREQ_TRIG_MHZ                   (20.0)
 
 //RADIOLIB_SX126X_CMD_SET_PA_CONFIG
 #define RADIOLIB_SX126X_PA_CONFIG_HP_MAX                        0x07
@@ -1195,6 +1196,15 @@ 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.
+      Will try to use Semtech-defined presets first, and if none of them matches,
+      custom iamge calibration will be attempted using calibrateImageRejection.
+      \param freq Frequency to perform the calibration for.
+      \returns \ref status_codes
+    */
+    int16_t calibrateImage(float freq);
+
     /*!
       \brief Perform image rejection calibration for the specified frequency band.
       WARNING: Use at your own risk! Setting incorrect values may lead to decreased performance
@@ -1246,6 +1256,7 @@ class SX126x: public PhysicalLayer {
 #endif
     const char* chipType = NULL;
     uint8_t bandwidth = 0;
+    float freqMHz = 0;
 
     // Allow subclasses to define different TX modes
     uint8_t txMode = Module::MODE_TX;
@@ -1276,7 +1287,6 @@ class SX126x: public PhysicalLayer {
 
     uint32_t tcxoDelay = 0;
     uint8_t pwr = 0;
-    uint32_t frf = 0;
 
     size_t implicitLen = 0;
     uint8_t invertIQEnabled = RADIOLIB_SX126X_LORA_IQ_STANDARD;

src/modules/SX126x/SX126x_LR_FHSS.cpp

@@ -355,7 +355,8 @@ int16_t SX126x::setLRFHSSHop(uint8_t index) {
   uint32_t nb_channel_in_grid = this->lrFhssGridNonFcc ? 8 : 52;
   uint32_t grid_offset = (1 + (this->lrFhssNgrid % 2)) * (nb_channel_in_grid / 2);
   uint32_t grid_in_pll_steps = this->lrFhssGridNonFcc ? 4096 : 26624;
-  uint32_t freq_raw = this->frf - freq_table * grid_in_pll_steps - grid_offset * 512;
+  uint32_t frf = (this->freqMHz * (uint32_t(1) << RADIOLIB_SX126X_DIV_EXPONENT)) / RADIOLIB_SX126X_CRYSTAL_FREQ;
+  uint32_t freq_raw = frf - freq_table * grid_in_pll_steps - grid_offset * 512;
 
   if((this->lrFhssHopNum < this->lrFhssHdrCount)) {
     if((((this->lrFhssHdrCount - this->lrFhssHopNum) % 2) == 0)) {