Added display API function to set LCD contrast

openrtx/include/interfaces/display.h

@@ -48,7 +48,7 @@
  *
  * NOTE: framebuffer allocation is the first operation performed, if fails an
  * error message is printed on the virtual COM port and this function returns
- * prematurely, without configuring the display. 
+ * prematurely, without configuring the display.
  * Thus, a dark screen can be symptom of failed allocation.
  */
 void display_init();
@@ -61,7 +61,7 @@ void display_init();
  * Changes to the framebuffer will not be reflected on the display until
  * display_render() or display_renderRows() are called.
  *
- * 
+ *
  * WARNING: no bound check is performed! Do not call free() on the pointer
  * returned, doing so will destroy the framebuffer!
  * @return pointer to framebuffer.
@@ -69,7 +69,7 @@ void display_init();
 void *display_getFrameBuffer();
 
 /**
- * When called, this function terminates the display driver 
+ * When called, this function terminates the display driver
  * and deallocates the framebuffer.
  */
 void display_terminate();
@@ -96,4 +96,12 @@ void display_render();
  */
 bool display_renderingInProgress();
 
+/**
+ * Set display contrast.
+ * NOTE: not all the display controllers support contrast control, thus on some
+ * targets this function has no effect.
+ * @param contrast: display contrast, normalised value with range 0 - 255.
+ */
+void display_setContrast(uint8_t contrast);
+
 #endif /* DISPLAY_H */

platform/drivers/display/HX83XX_MDx.c

@@ -384,7 +384,7 @@ void display_renderRows(uint8_t startRow, uint8_t endRow)
      * this one is made of 16 bit variables.
      */
     DMA2_Stream7->NDTR = (endRow - startRow) * SCREEN_WIDTH * sizeof(uint16_t);
-    DMA2_Stream7->PAR  = ((uint32_t ) frameBuffer + (startRow * SCREEN_WIDTH 
+    DMA2_Stream7->PAR  = ((uint32_t ) frameBuffer + (startRow * SCREEN_WIDTH
                                                      * sizeof(uint16_t)));
     DMA2_Stream7->M0AR = LCD_FSMC_ADDR_DATA;
     DMA2_Stream7->CR = DMA_SxCR_CHSEL         /* Channel 7                   */
@@ -418,3 +418,9 @@ void *display_getFrameBuffer()
 {
     return (void *)(frameBuffer);
 }
+
+void display_setContrast(uint8_t contrast)
+{
+    /* This controller does not support contrast regulation */
+    (void) contrast;
+}

platform/drivers/display/UC1701_GD77.c

@@ -91,11 +91,9 @@ void display_init()
     gpio_clearPin(LCD_CS);
 
     gpio_clearPin(LCD_RS);      /* RS low -> command mode          */
-//     sendByteToController(0xE2); /* System Reset                 */
     sendByteToController(0x2F); /* Voltage Follower On             */
-    sendByteToController(0x81); /* Set Electronic Volume = 15      */
+    sendByteToController(0x81); /* Set Electronic Volume           */
-    /* TODO variable contrast */
+    sendByteToController(0x15); /* Contrast, initial setting       */
-    sendByteToController(0x15); /* Contrast                        */
     sendByteToController(0xA2); /* Set Bias = 1/9                  */
     sendByteToController(0xA1); /* A0 Set SEG Direction            */
     sendByteToController(0xC0); /* Set COM Direction               */
@@ -130,7 +128,9 @@ void display_renderRow(uint8_t row)
                 count--;
             }
         }
-        for (uint8_t s = 0; s < 8; s++){
+
+        for (uint8_t s = 0; s < 8; s++)
+        {
             sendByteToController(tmp[s]);
         }
     }
@@ -138,7 +138,7 @@ void display_renderRow(uint8_t row)
 
 void display_renderRows(uint8_t startRow, uint8_t endRow)
 {
-        for(uint8_t row = startRow; row < endRow; row++)
+    for(uint8_t row = startRow; row < endRow; row++)
     {
         gpio_clearPin(LCD_RS);            /* RS low -> command mode */
         sendByteToController(0xB0 | row); /* Set Y position         */
@@ -147,7 +147,7 @@ void display_renderRows(uint8_t startRow, uint8_t endRow)
         gpio_setPin(LCD_RS);              /* RS high -> data mode   */
         display_renderRow(row);
     }
-        
+
 }
 
 void display_render()
@@ -166,3 +166,10 @@ void *display_getFrameBuffer()
 {
     return (void *)(frameBuffer);
 }
+
+void display_setContrast(uint8_t contrast)
+{
+    gpio_clearPin(LCD_RS);               /* RS low -> command mode              */
+    sendByteToController(0x81);          /* Set Electronic Volume               */
+    sendByteToController(contrast >> 2); /* Controller contrast range is 0 - 63 */
+}

platform/drivers/display/display_libSDL.c

@@ -196,3 +196,9 @@ void *display_getFrameBuffer()
 {
     return (void *) (frameBuffer);
 }
+
+void display_setContrast(uint8_t contrast)
+{
+    printf("Setting display contrast to %d\n", contrast);
+}
+