Add left and right volume balance enhancement (#53)

Enhancement for adjusting the left and right volume balance.
by: fabitom

Author: fabitom

src/VS1053.cpp

@@ -189,12 +189,32 @@ void VS1053::begin() {
 void VS1053::setVolume(uint8_t vol) {
     // Set volume.  Both left and right.
     // Input value is 0..100.  100 is the loudest.
-    uint16_t value; // Value to send to SCI_VOL
+    uint8_t valueL, valueR; // Values to send to SCI_VOL
 
     curvol = vol;                         // Save for later use
-    value = map(vol, 0, 100, 0xFF, 0x00); // 0..100% to one channel
-    value = (value << 8) | value;
-    write_register(SCI_VOL, value); // Volume left and right
+    valueL = vol;
+    valueR = vol;
+
+    if (curbalance < 0) {
+        valueR = max(0, vol + curbalance);
+    } else if (curbalance > 0) {
+        valueL = max(0, vol - curbalance);
+    }
+
+    valueL = map(valueL, 0, 100, 0xFE, 0x00); // 0..100% to left channel
+    valueR = map(valueR, 0, 100, 0xFE, 0x00); // 0..100% to right channel
+
+    write_register(SCI_VOL, (valueL << 8) | valueR); // Volume left and right
+}
+
+void VS1053::setBalance(int8_t balance) {
+    if (balance > 100) {
+        curbalance = 100;
+    } else if (balance < -100) {
+        curbalance = -100;
+    } else {
+        curbalance = balance;
+    }
 }
 
 void VS1053::setTone(uint8_t *rtone) { // Set bass/treble (4 nibbles)
@@ -212,6 +232,10 @@ uint8_t VS1053::getVolume() { // Get the currenet volume setting.
     return curvol;
 }
 
+int8_t VS1053::getBalance() { // Get the currenet balance setting.
+    return curbalance;
+}
+
 void VS1053::startSong() {
     sdi_send_fillers(10);
 }

src/VS1053.h

@@ -44,6 +44,8 @@ class VS1053 {
     uint8_t dcs_pin;                        // Pin where DCS line is connected
     uint8_t dreq_pin;                       // Pin where DREQ line is connected
     uint8_t curvol;                         // Current volume setting 0..100%
+    int8_t  curbalance = 0;                 // Current balance setting -100..100
+                                            // (-100 = right channel silent, 100 = left channel silent)
     const uint8_t vs1053_chunk_size = 32;
     // SCI Register
     const uint8_t SCI_MODE = 0x0;
@@ -127,12 +129,18 @@ class VS1053 {
     // Set the player volume.Level from 0-100, higher is louder
     void setVolume(uint8_t vol);
 
+    // Adjusting the left and right volume balance, higher to enhance the right side, lower to enhance the left side.
+    void setBalance(int8_t balance);
+
     // Set the player baas/treble, 4 nibbles for treble gain/freq and bass gain/freq
     void setTone(uint8_t *rtone);
 
     // Get the currenet volume setting, higher is louder
     uint8_t getVolume();
 
+    // Get the currenet balance setting (-100..100)
+    int8_t getBalance();
+
     // Print configuration details to serial output.
     void printDetails(const char *header);