From 4446a3781c3f4a61eacbffe20c002f7130a5c70c Mon Sep 17 00:00:00 2001
From: Jack Humbert <jack.humb@gmail.com>
Date: Thu, 11 Oct 2018 13:06:17 -0400
Subject: [PATCH] faster buffer sending

---
 drivers/qwiic/micro_oled.c | 26 +++++++++++++++++++-------
 drivers/qwiic/micro_oled.h |  1 +
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/qwiic/micro_oled.c b/drivers/qwiic/micro_oled.c
index 46765f389c6..1e6ed100050 100644
--- a/drivers/qwiic/micro_oled.c
+++ b/drivers/qwiic/micro_oled.c
@@ -43,6 +43,7 @@ uint16_t fontMapWidth;
 #define swap(a, b) { uint8_t t = a; a = b; b = t; }
 
 uint8_t micro_oled_transfer_buffer[20];
+static uint8_t micro_oled_screen_current[384] = { 0 };
 static uint8_t micro_oled_screen_buffer[] = {
 /* LCD Memory organised in 64 horizontal pixel and 6 rows of byte
    B  B .............B  -----
@@ -145,7 +146,7 @@ void micro_oled_init(void) {
   send_command(0x40);
 
   send_command(DISPLAYON);       //--turn on oled panel
-  //clear_screen();           // Erase hardware memory inside the OLED controller to avoid random data in memory.
+  clear_screen();           // Erase hardware memory inside the OLED controller to avoid random data in memory.
   send_buffer();
 }
 
@@ -217,19 +218,30 @@ void set_contrast(uint8_t contrast) {
 }
 
 /** \brief Transfer display buffer.
-  Bulk move the screen buffer to the SSD1306 controller's memory so that images/graphics drawn on the screen buffer will be displayed on the OLED.
+  Sends the updated buffer to the controller - the current status is checked before to save i2c exectution time
 */
 void send_buffer(void) {
   uint8_t i, j;
 
-  for (i=0; i<6; i++) {
-    set_page_address(i);
-    set_column_address(0);
-    for (j=0;j<0x40;j++) {
-      send_data(micro_oled_screen_buffer[i*0x40+j]);
+  uint8_t page_addr = 0xFF;
+  for (i = 0; i < 6; i++) {
+    uint8_t col_addr = 0xFF;
+    for (j = 0; j < 0x40; j++) {
+      if (micro_oled_screen_buffer[i*0x40+j] != micro_oled_screen_current[i*0x40+j]) {
+        if (page_addr != i) {
+          set_page_address(i);
+        }
+        if (col_addr != j) {
+          set_column_address(j);
+        }
+        send_data(micro_oled_screen_buffer[i*0x40+j]);
+        micro_oled_screen_current[i*0x40+j] = micro_oled_screen_buffer[i*0x40+j];
+        col_addr = j + 1;
+      }
     }
   }
 }
+
 /** \brief Draw pixel with color and mode.
   Draw color pixel in the screen buffer's x,y position with NORM or XOR draw mode.
 */
diff --git a/drivers/qwiic/micro_oled.h b/drivers/qwiic/micro_oled.h
index faa06313d11..8303b3910d5 100644
--- a/drivers/qwiic/micro_oled.h
+++ b/drivers/qwiic/micro_oled.h
@@ -37,6 +37,7 @@ void send_command(uint8_t command);
 void send_data(uint8_t data);
 void set_page_address(uint8_t address);
 void set_column_address(uint8_t address);
+void clear_screen(void);
 void clear_buffer(void);
 void send_buffer(void);
 void draw_pixel(uint8_t x, uint8_t y, uint8_t color, uint8_t mode);