Tom Skevington (ALT) / Mbed OS DISCOF746NG_LCD_Scratch

Code to replicate double-draw glitch on ST dev board. Program draws full-screen Red->Green->Blue into back-buffer, then swaps the LTDC layer source buffer before repeating. This should result in a solid blue screen, but produces a visible glitch with parts of the screen flashing red and green.

Dependencies:   BSP_DISCO_F746NG

Diff: main.cpp

Revision:
2:a19deff061e8
Parent:
1:d515deceeccc
Child:
3:5ceff0955fb1
--- a/main.cpp	Fri Mar 27 07:18:57 2020 +0000
+++ b/main.cpp	Fri Mar 27 07:39:08 2020 +0000
@@ -1,6 +1,10 @@
 #include "mbed.h"
 #include "stm32746g_discovery_sdram.h"
 
+//If 0 then always draw to front buffer
+//else always draw to back buffer
+#define DOUBLE_BUFFER 0
+
 const uint32_t SDRAM_BANK1_ADDR=0xC0000000;
 const uint32_t SDRAM_BANK_SIZE =0x200000;
 const uint32_t SDRAM_BANK2_ADDR=SDRAM_BANK1_ADDR+SDRAM_BANK_SIZE;
@@ -170,6 +174,7 @@
 void transferCompleteHandler() {
 
     queue->call(printf,"TC\n");
+    #if DOUBLE_BUFFER
     if(updated==2) {
         swapping=false;
         updated=0;
@@ -177,12 +182,19 @@
         cont=false;
     }
     if(line||(buffer.empty()&&(updated>0))) flip(); else draw();
+    #else
+    draw();
+    #endif
 }
 
 void lineHandler() {
     
     queue->call(printf,"LN\n");
+    #if DOUBLE_BUFFER
     if(running==true) line=true; else if(updated>0) flip(); else draw();
+    #else
+    draw();
+    #endif
 }
 
 void flip() {
@@ -219,6 +231,9 @@
     if(DMA2D->CR&0x01) return false;
     if(buffer.empty()) {
         running=false;
+        #if !DOUBLE_BUFFER
+        cont=false;
+        #endif
         return false;
     }
     queue->call(printf,"DRAW\n");
@@ -227,7 +242,11 @@
     buffer.pop(color);
     DMA2D->OPFCCR=2;
     DMA2D->OCOLR=(uint32_t)color;
+    #if DOUBLE_BUFFER
     DMA2D->OMAR=backBuffer;
+    #else
+    DMA2D->OMAR=frontBuffer;
+    #endif
     DMA2D->OOR=0;
     DMA2D->NLR=(((uint32_t)LCD_WIDTH)<<16)|((uint32_t)(LCD_HEIGHT));
     DMA2D->IFCR=0x3F;
@@ -252,6 +271,9 @@
         color=0x001F;
         buffer.push(color);
         cont=true;
+        #if !DOUBLE_BUFFER
+        ThisThread::sleep_for(100);
+        #endif
     }
 }