added functionality for just a port

quantum/quantum.c

@@ -594,19 +594,29 @@ static const uint8_t backlight_pin = BACKLIGHT_PIN;
 #  define COM1x1 COM1A1
 #  define OCR1x  OCR1A
 #else
-#  error "Backlight pin not supported - use B5, B6, or B7"
+#  define NO_BACKLIGHT_CLOCK
+#endif
+
+#ifndef BACKLIGHT_ON_STATE
+#define BACKLIGHT_ON_STATE 0
 #endif
 
 __attribute__ ((weak))
 void backlight_init_ports(void)
 {
 
-  // Setup backlight pin as output and output low.
+  // Setup backlight pin as output and output to on state.
   // DDRx |= n
   _SFR_IO8((backlight_pin >> 4) + 1) |= _BV(backlight_pin & 0xF);
+  #if BACKLIGHT_ON_STATE == 0
     // PORTx &= ~n
     _SFR_IO8((backlight_pin >> 4) + 2) &= ~_BV(backlight_pin & 0xF);
+  #else
+    // PORTx |= n
+    _SFR_IO8((backlight_pin >> 4) + 2) |= _BV(backlight_pin & 0xF);
+  #endif
 
+  #ifndef NO_BACKLIGHT_CLOCK
     // Use full 16-bit resolution.
     ICR1 = 0xFFFF;
 
@@ -622,6 +632,7 @@ void backlight_init_ports(void)
 
     TCCR1A = _BV(COM1x1) | _BV(WGM11); // = 0b00001010;
     TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001;
+  #endif
 
   backlight_init();
   #ifdef BACKLIGHT_BREATHING
@@ -633,24 +644,43 @@ __attribute__ ((weak))
 void backlight_set(uint8_t level)
 {
   // Prevent backlight blink on lowest level
+  #if BACKLIGHT_ON_STATE == 0
     // PORTx &= ~n
     _SFR_IO8((backlight_pin >> 4) + 2) &= ~_BV(backlight_pin & 0xF);
+  #else
+    // PORTx |= n
+    _SFR_IO8((backlight_pin >> 4) + 2) |= _BV(backlight_pin & 0xF);
+  #endif
 
   if ( level == 0 ) {
+    #ifndef NO_BACKLIGHT_CLOCK
       // Turn off PWM control on backlight pin, revert to output low.
       TCCR1A &= ~(_BV(COM1x1));
       OCR1x = 0x0;
-  } else if ( level == BACKLIGHT_LEVELS ) {
+    #else
+      #if BACKLIGHT_ON_STATE == 0
+        // PORTx |= n
+        _SFR_IO8((backlight_pin >> 4) + 2) |= _BV(backlight_pin & 0xF);
+      #else
+        // PORTx &= ~n
+        _SFR_IO8((backlight_pin >> 4) + 2) &= ~_BV(backlight_pin & 0xF);
+      #endif
+    #endif
+  } 
+  #ifndef NO_BACKLIGHT_CLOCK
+    else if ( level == BACKLIGHT_LEVELS ) {
       // Turn on PWM control of backlight pin
       TCCR1A |= _BV(COM1x1);
       // Set the brightness
       OCR1x = 0xFFFF;
-  } else {
+    } 
+    else {
       // Turn on PWM control of backlight pin
       TCCR1A |= _BV(COM1x1);
       // Set the brightness
       OCR1x = 0xFFFF >> ((BACKLIGHT_LEVELS - level) * ((BACKLIGHT_LEVELS + 1) / 2));
     }
+  #endif
 
   #ifdef BACKLIGHT_BREATHING
     breathing_intensity_default();