From 73d8b794ed7faf470a4854cf0cd112edf6bf0e09 Mon Sep 17 00:00:00 2001
From: melektron <developer@elektron.work>
Date: Mon, 15 Aug 2022 16:03:51 +0200
Subject: [PATCH] Fix drawWedgeLine for parallel interface Added (and
 restructured) missing code to reinitiate a previous transaction in the
 readPixel method when operating in 8 bit parallel mode. This mistake caused
 the CS line to be set to high after the first pixel read without setting it
 back to low to continue drawing the wedge line (or wide line, spot, ...) when
 operating in 8 bit parallel mode.

---
 TFT_eSPI.cpp | 77 +++++++++++++++++++++++++++++++---------------------
 1 file changed, 46 insertions(+), 31 deletions(-)

diff --git a/TFT_eSPI.cpp b/TFT_eSPI.cpp
index 14eea87..96365c7 100644
--- a/TFT_eSPI.cpp
+++ b/TFT_eSPI.cpp
@@ -1069,9 +1069,24 @@ uint16_t TFT_eSPI::readPixel(int32_t x0, int32_t y0)
   // Range checking
   if ((x0 < _vpX) || (y0 < _vpY) ||(x0 >= _vpW) || (y0 >= _vpH)) return 0;
 
-#if defined(TFT_PARALLEL_8_BIT) || defined(RP2040_PIO_INTERFACE)
+  // Temporary color variable because different driver ICs use different
+  // bit order in colors
+  uint16_t color = 0;
 
-  CS_L;
+  // This function can get called during anti-aliased font rendering
+  // so a transaction may be in progress. The old transaction state
+  // has to be saved so it can be restored before returning
+  bool wasInTransaction = inTransaction;
+  if (inTransaction)
+  {
+    inTransaction = false;
+    end_tft_write();
+  }
+
+  // set CS low and initialize SPI for reading if required
+  begin_tft_read();
+
+#if defined(TFT_PARALLEL_8_BIT) || defined(RP2040_PIO_INTERFACE)
 
   readAddrWindow(x0, y0, 1, 1);
 
@@ -1089,45 +1104,24 @@ uint16_t TFT_eSPI::readPixel(int32_t x0, int32_t y0)
   #if defined (ILI9341_DRIVER)  || defined(ILI9341_2_DRIVER) || defined (ILI9488_DRIVER) || defined (SSD1963_DRIVER)// Read 3 bytes
 
     // Read window pixel 24 bit RGB values and fill in LS bits
-    uint16_t rgb = ((readByte() & 0xF8) << 8) | ((readByte() & 0xFC) << 3) | (readByte() >> 3);
-
-    CS_H;
-
-    // Set masked pins D0- D7 to output
-    busDir(dir_mask, OUTPUT);
-
-    return rgb;
+    color = ((readByte() & 0xF8) << 8) | ((readByte() & 0xFC) << 3) | (readByte() >> 3);
 
   #else // ILI9481 or ILI9486 16 bit read
 
     // Fetch the 16 bit BRG pixel
     uint16_t bgr = (readByte() << 8) | readByte();
 
-    CS_H;
-
-    // Set masked pins D0- D7 to output
-    busDir(dir_mask, OUTPUT);
-
     #ifdef ILI9486_DRIVER
-      return  bgr;
+      color = bgr;
     #else
       // Swap Red and Blue (could check MADCTL setting to see if this is needed)
-      return  (bgr>>11) | (bgr<<11) | (bgr & 0x7E0);
+      color = (bgr>>11) | (bgr<<11) | (bgr & 0x7E0);
     #endif
 
   #endif
 
 #else // Not TFT_PARALLEL_8_BIT
 
-  // This function can get called during anti-aliased font rendering
-  // so a transaction may be in progress
-  bool wasInTransaction = inTransaction;
-  if (inTransaction) { inTransaction= false; end_tft_write();}
-
-  uint16_t color = 0;
-
-  begin_tft_read(); // Sets CS low
-
   readAddrWindow(x0, y0, 1, 1);
 
   #ifdef TFT_SDA_READ
@@ -1163,20 +1157,41 @@ uint16_t TFT_eSPI::readPixel(int32_t x0, int32_t y0)
 
   #endif
 */
-  CS_H;
 
   #ifdef TFT_SDA_READ
     end_SDA_Read();
   #endif
 
+#endif
+
+  // sets CS high (and reconfigures SPI bus if required)
+  // if no transaction is in progress as might be with anti-aliased
+  // drawing methods.
   end_tft_read();
 
-  // Reinstate the transaction if one was in progress
-  if(wasInTransaction) { begin_tft_write(); inTransaction = true; }
+#if defined(TFT_PARALLEL_8_BIT) || defined(RP2040_PIO_INTERFACE)
+  // in parallel mode, the data pins should be set to output
+  // when reading is complete:
+  // Set masked pins D0- D7 to output
+  busDir(dir_mask, OUTPUT);
+#endif
+
+  // Reinstate the transaction if one was in progress before calling
+  // this method
+  if (wasInTransaction)
+  {
+    begin_tft_write();
+    inTransaction = true;
+  }
+
+  /*
+  NOTE:
+  ending the tft read and subsequently restarting the tft write
+  may cause a short high pulse on the CS line which could confuse
+  tft drivers (not tested).
+  */
 
   return color;
-
-#endif
 }
 
 void TFT_eSPI::setCallback(getColorCallback getCol)