added functionality for just a port

quantum/quantum.c

@@ -594,34 +594,45 @@ 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);
-  // PORTx &= ~n
-  _SFR_IO8((backlight_pin >> 4) + 2) &= ~_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
 
-  // Use full 16-bit resolution.
-  ICR1 = 0xFFFF;
+  #ifndef NO_BACKLIGHT_CLOCK
+    // Use full 16-bit resolution.
+    ICR1 = 0xFFFF;
 
-  // I could write a wall of text here to explain... but TL;DW
-  // Go read the ATmega32u4 datasheet.
-  // And this: http://blog.saikoled.com/post/43165849837/secret-konami-cheat-code-to-high-resolution-pwm-on
+    // I could write a wall of text here to explain... but TL;DW
+    // Go read the ATmega32u4 datasheet.
+    // And this: http://blog.saikoled.com/post/43165849837/secret-konami-cheat-code-to-high-resolution-pwm-on
 
-  // Pin PB7 = OCR1C (Timer 1, Channel C)
-  // Compare Output Mode = Clear on compare match, Channel C = COM1C1=1 COM1C0=0
-  // (i.e. start high, go low when counter matches.)
-  // WGM Mode 14 (Fast PWM) = WGM13=1 WGM12=1 WGM11=1 WGM10=0
-  // Clock Select = clk/1 (no prescaling) = CS12=0 CS11=0 CS10=1
+    // Pin PB7 = OCR1C (Timer 1, Channel C)
+    // Compare Output Mode = Clear on compare match, Channel C = COM1C1=1 COM1C0=0
+    // (i.e. start high, go low when counter matches.)
+    // WGM Mode 14 (Fast PWM) = WGM13=1 WGM12=1 WGM11=1 WGM10=0
+    // Clock Select = clk/1 (no prescaling) = CS12=0 CS11=0 CS10=1
 
-  TCCR1A = _BV(COM1x1) | _BV(WGM11); // = 0b00001010;
-  TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001;
+    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
-  // PORTx &= ~n
-  _SFR_IO8((backlight_pin >> 4) + 2) &= ~_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
 
   if ( level == 0 ) {
-    // Turn off PWM control on backlight pin, revert to output low.
-    TCCR1A &= ~(_BV(COM1x1));
-    OCR1x = 0x0;
-  } else if ( level == BACKLIGHT_LEVELS ) {
-    // Turn on PWM control of backlight pin
-    TCCR1A |= _BV(COM1x1);
-    // Set the brightness
-    OCR1x = 0xFFFF;
-  } else {
-    // Turn on PWM control of backlight pin
-    TCCR1A |= _BV(COM1x1);
-    // Set the brightness
-    OCR1x = 0xFFFF >> ((BACKLIGHT_LEVELS - level) * ((BACKLIGHT_LEVELS + 1) / 2));
+    #ifndef NO_BACKLIGHT_CLOCK
+      // Turn off PWM control on backlight pin, revert to output low.
+      TCCR1A &= ~(_BV(COM1x1));
+      OCR1x = 0x0;
+    #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 {
+      // 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();