From 7eb9f3f10d27be67bfd215cadc2daff01caf99d2 Mon Sep 17 00:00:00 2001
From: "Ben V. Brown" <Ralim@Ralimtek.com>
Date: Sun, 6 Nov 2022 22:10:09 +1100
Subject: [PATCH 1/2] Only send on display change

---
 source/Core/Drivers/OLED.cpp |  4 ++--
 source/Core/Drivers/OLED.hpp | 17 +++++++++++++----
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/source/Core/Drivers/OLED.cpp b/source/Core/Drivers/OLED.cpp
index 6ca691db07..54574248fc 100644
--- a/source/Core/Drivers/OLED.cpp
+++ b/source/Core/Drivers/OLED.cpp
@@ -25,7 +25,7 @@ bool               OLED::initDone = false;
 uint8_t            OLED::displayOffset;
 uint8_t            OLED::screenBuffer[16 + (OLED_WIDTH * 2) + 10]; // The data buffer
 uint8_t            OLED::secondFrameBuffer[OLED_WIDTH * 2];
-
+uint32_t           OLED::displayChecksum;
 /*Setup params for the OLED screen*/
 /*http://www.displayfuture.com/Display/datasheet/controller/SSD1307.pdf*/
 /*All commands are prefixed with 0x80*/
@@ -222,7 +222,7 @@ void OLED::maskScrollIndicatorOnOLED() {
   // it from the screen buffer which is updated by `OLED::setRotation`.
   uint8_t rightmostColumn = screenBuffer[7];
   uint8_t maskCommands[]  = {
-      // Set column address:
+       // Set column address:
       //  A[6:0] - Column start address = rightmost column
       //  B[6:0] - Column end address = rightmost column
       0x80,
diff --git a/source/Core/Drivers/OLED.hpp b/source/Core/Drivers/OLED.hpp
index f088f91a23..b6b6743a95 100644
--- a/source/Core/Drivers/OLED.hpp
+++ b/source/Core/Drivers/OLED.hpp
@@ -47,11 +47,19 @@ class OLED {
 
   static void initialize(); // Startup the I2C coms (brings screen out of reset etc)
   static bool isInitDone();
-  // Draw the buffer out to the LCD using the DMA Channel
+  // Draw the buffer out to the LCD if any content has changed.
   static void refresh() {
-    I2C_CLASS::Transmit(DEVICEADDR_OLED, screenBuffer, FRAMEBUFFER_START + (OLED_WIDTH * 2));
-    // DMA tx time is ~ 20mS Ensure after calling this you delay for at least 25ms
-    // or we need to goto double buffering
+    uint32_t  hash = 0;
+    const int len  = FRAMEBUFFER_START + (OLED_WIDTH * 2);
+    for (int i = 0; i < len; i++) {
+      hash += (i * screenBuffer[i]);
+    }
+    if (hash != displayChecksum) {
+      displayChecksum = hash;
+      I2C_CLASS::Transmit(DEVICEADDR_OLED, screenBuffer, len);
+      // DMA tx time is ~ 20mS Ensure after calling this you delay for at least 25ms
+      // or we need to goto double buffering
+    }
   }
 
   static void setDisplayState(DisplayState state) {
@@ -112,6 +120,7 @@ class OLED {
   static DisplayState displayState;
   static int16_t      cursor_x, cursor_y;
   static uint8_t      displayOffset;
+  static uint32_t     displayChecksum;
   static uint8_t      screenBuffer[16 + (OLED_WIDTH * 2) + 10]; // The data buffer
   static uint8_t      secondFrameBuffer[OLED_WIDTH * 2];
 };

From 80e7ab3161112d1841b19f8aded3cca21eb5021b Mon Sep 17 00:00:00 2001
From: "Ben V. Brown" <Ralim@Ralimtek.com>
Date: Sun, 6 Nov 2022 22:51:59 +1100
Subject: [PATCH 2/2] Force delay after display state change

So that we backoff if OLED is busy

Update OLED.hpp
---
 source/Core/Drivers/OLED.hpp | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/source/Core/Drivers/OLED.hpp b/source/Core/Drivers/OLED.hpp
index b6b6743a95..9912c5df70 100644
--- a/source/Core/Drivers/OLED.hpp
+++ b/source/Core/Drivers/OLED.hpp
@@ -10,10 +10,12 @@
 #ifndef OLED_HPP_
 #define OLED_HPP_
 #include "Font.h"
+#include "cmsis_os.h"
 #include "configuration.h"
 #include <BSP.h>
 #include <stdbool.h>
 #include <string.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -63,8 +65,13 @@ class OLED {
   }
 
   static void setDisplayState(DisplayState state) {
-    displayState    = state;
-    screenBuffer[1] = (state == ON) ? 0xAF : 0xAE;
+    if (state != displayState) {
+      displayState    = state;
+      screenBuffer[1] = (state == ON) ? 0xAF : 0xAE;
+      // Dump the screen state change out _now_
+      I2C_CLASS::Transmit(DEVICEADDR_OLED, screenBuffer, FRAMEBUFFER_START - 1);
+      osDelay(TICKS_10MS);
+    }
   }
 
   static void setRotation(bool leftHanded); // Set the rotation for the screen