st7789: add support for 3 wire interface

3 wire interface for ST7789 LCD controller does not use  CMD/DATA pin to
specify whether data  or command is send but uses 9th bit of SPI transfer.

This commit adds support for 3 wire interface to ST7789 controller.

Signed-off-by: Michal Lenc <michallenc@seznam.cz>

drivers/lcd/Kconfig

@@ -705,6 +705,14 @@ config LCD_ST7789
 	default n
 
 if LCD_ST7789
+config LCD_ST7789_3WIRE
+	bool "Use 3 wire interface"
+	default n
+	---help---
+		Specifies whether 3 wire or 4 wire (default) interface is
+		used. 3 wire interface drops CMD/DATA pin and uses 9th bit
+		to determine data/command message.
+
 config LCD_ST7789_XRES
 	int "ST7789 X Resolution"
 	default 240

drivers/lcd/st7789.c

@@ -45,9 +45,9 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-/* CONFIG_SPI_CMDDATA has to be set */
+/* CONFIG_SPI_CMDDATA has to be set for 4 wire interface */
 
-#ifndef CONFIG_SPI_CMDDATA
+#if !defined(CONFIG_LCD_ST7789_3WIRE) && !defined(CONFIG_SPI_CMDDATA)
 #  error "CONFIG_SPI_CMDDATA option has to be set for SPI communication"
 #endif
 
@@ -103,6 +103,18 @@
 #  define CONFIG_LCD_RPORTRAIT 1
 #endif
 
+/* Define prefixes for 3 wire communication if used */
+
+#ifdef CONFIG_LCD_ST7789_3WIRE
+#  define LCD_ST7789_SPI_BITS 9
+#  define LCD_ST7789_DATA_PREFIX (1 << 8)
+#  define LCD_ST7789_CMD_PREFIX  (0 << 8)
+#else
+#  define LCD_ST7789_SPI_BITS 8
+#  define LCD_ST7789_DATA_PREFIX (0)
+#  define LCD_ST7789_CMD_PREFIX  (0)
+#endif
+
 /* Display Resolution */
 
 #if !defined(CONFIG_LCD_ST7789_XRES)
@@ -184,6 +196,18 @@ struct st7789_dev_s
   uint16_t runbuffer[ST7789_LUT_SIZE];
 };
 
+  /* 3 wire interface for ST7789 requires the driver to send information
+   * about command/data transfer as 9th bit of SPI transfer. This would
+   * require non standard SPI interface that is not supported so a little
+   * workaround is used here (inspire by SSD1351 driver). We split our
+   * buffer into rows and send those rows separately with added 9th bit.
+   * The price for this is a small overhead in SPI communication.
+   */
+
+#ifdef CONFIG_LCD_ST7789_3WIRE
+uint16_t rowbuff[ST7789_XRES * ST7789_BYTESPP];
+#endif
+
 /****************************************************************************
  * Private Function Protototypes
  ****************************************************************************/
@@ -325,11 +349,23 @@ static void st7789_deselect(FAR struct spi_dev_s *spi)
 
 static inline void st7789_sendcmd(FAR struct st7789_dev_s *dev, uint8_t cmd)
 {
-  st7789_select(dev->spi, 8);
+#ifdef CONFIG_LCD_ST7789_3WIRE
+  uint16_t txbuf;
+
+  /* Add command prefix (9th bit shoudl be 0 ) */
+
+  txbuf = LCD_ST7789_CMD_PREFIX | cmd;
+
+  st7789_select(dev->spi, LCD_ST7789_SPI_BITS);
+  SPI_SEND(dev->spi, txbuf);
+  st7789_deselect(dev->spi);
+#else
+  st7789_select(dev->spi, LCD_ST7789_SPI_BITS);
   SPI_CMDDATA(dev->spi, SPIDEV_DISPLAY(0), true);
   SPI_SEND(dev->spi, cmd);
   SPI_CMDDATA(dev->spi, SPIDEV_DISPLAY(0), false);
   st7789_deselect(dev->spi);
+#endif
 }
 
 /****************************************************************************
@@ -380,26 +416,26 @@ static void st7789_setorientation(FAR struct st7789_dev_s *dev,
   if (orientation != LCD_PORTRAIT)
     {
       st7789_sendcmd(dev, ST7789_MADCTL);
-      st7789_select(dev->spi, 8);
+      st7789_select(dev->spi, LCD_ST7789_SPI_BITS);
     }
 
   if (orientation == LCD_RLANDSCAPE)
     {
       /* RLANDSCAPE : MY=1 MV=1 */
 
-      SPI_SEND(dev->spi, 0xa0);
+      SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | 0xa0);
     }
   else if (orientation == LCD_LANDSCAPE)
     {
       /* LANDSCAPE : MX=1 MV=1 */
 
-      SPI_SEND(dev->spi, 0x70);
+      SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | 0x70);
     }
   else if (orientation == LCD_RPORTRAIT)
     {
       /* RPORTRAIT : MX=1 MY=1 */
 
-      SPI_SEND(dev->spi, 0xc0);
+      SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | 0xc0);
     }
 
   st7789_deselect(dev->spi);
@@ -412,7 +448,7 @@ static void st7789_setorientation(FAR struct st7789_dev_s *dev)
   uint8_t madctl = 0x00;
 
   st7789_sendcmd(dev, ST7789_MADCTL);
-  st7789_select(dev->spi, 8);
+  st7789_select(dev->spi, LCD_ST7789_SPI_BITS);
 
 #if !defined(CONFIG_LCD_PORTRAIT)
 
@@ -444,7 +480,7 @@ static void st7789_setorientation(FAR struct st7789_dev_s *dev)
   madctl ^= 0x80;
 #endif
 
-  SPI_SEND(dev->spi, madctl);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | madctl);
 
   st7789_deselect(dev->spi);
 }
@@ -465,34 +501,38 @@ static void st7789_setarea(FAR struct st7789_dev_s *dev,
   /* Set row address */
 
   st7789_sendcmd(dev, ST7789_RASET);
-  st7789_select(dev->spi, 8);
+  st7789_select(dev->spi, LCD_ST7789_SPI_BITS);
 #ifdef CONFIG_LCD_DYN_ORIENTATION
-  SPI_SEND(dev->spi, (y0 + g_lcddev.yoff) >> 8);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((y0 + g_lcddev.yoff) >> 8));
-  SPI_SEND(dev->spi, (y0 + g_lcddev.yoff) & 0xff);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((y0 + g_lcddev.yoff) & 0xff));
-  SPI_SEND(dev->spi, (y1 + g_lcddev.yoff) >> 8);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((y1 + g_lcddev.yoff) >> 8));
-  SPI_SEND(dev->spi, (y1 + g_lcddev.yoff) & 0xff);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((y1 + g_lcddev.yoff) & 0xff));
 #else
-  SPI_SEND(dev->spi, (y0 + ST7789_YOFFSET) >> 8);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((y0 + ST7789_YOFFSET) >> 8));
-  SPI_SEND(dev->spi, (y0 + ST7789_YOFFSET) & 0xff);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX |
-  SPI_SEND(dev->spi, (y1 + ST7789_YOFFSET) >> 8);
+                     ((y0 + ST7789_YOFFSET) & 0xff));
-  SPI_SEND(dev->spi, (y1 + ST7789_YOFFSET) & 0xff);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((y1 + ST7789_YOFFSET) >> 8));
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX |
+                     ((y1 + ST7789_YOFFSET) & 0xff));
 #endif
   st7789_deselect(dev->spi);
 
   /* Set column address */
 
   st7789_sendcmd(dev, ST7789_CASET);
-  st7789_select(dev->spi, 8);
+  st7789_select(dev->spi, LCD_ST7789_SPI_BITS);
 #ifdef CONFIG_LCD_DYN_ORIENTATION
-  SPI_SEND(dev->spi, (x0 + g_lcddev.xoff) >> 8);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((x0 + g_lcddev.xoff) >> 8));
-  SPI_SEND(dev->spi, (x0 + g_lcddev.xoff) & 0xff);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((x0 + g_lcddev.xoff) & 0xff));
-  SPI_SEND(dev->spi, (x1 + g_lcddev.xoff) >> 8);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((x1 + g_lcddev.xoff) >> 8));
-  SPI_SEND(dev->spi, (x1 + g_lcddev.xoff) & 0xff);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((x1 + g_lcddev.xoff) & 0xff));
 #else
-  SPI_SEND(dev->spi, (x0 + ST7789_XOFFSET) >> 8);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((x0 + ST7789_XOFFSET) >> 8));
-  SPI_SEND(dev->spi, (x0 + ST7789_XOFFSET) & 0xff);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX |
-  SPI_SEND(dev->spi, (x1 + ST7789_XOFFSET) >> 8);
+                     ((x0 + ST7789_XOFFSET) & 0xff));
-  SPI_SEND(dev->spi, (x1 + ST7789_XOFFSET) & 0xff);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | ((x1 + ST7789_XOFFSET) >> 8));
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX |
+                     ((x1 + ST7789_XOFFSET) & 0xff));
 #endif
   st7789_deselect(dev->spi);
 }
@@ -513,8 +553,8 @@ static void st7789_bpp(FAR struct st7789_dev_s *dev, int bpp)
 
   depth = bpp >> 2 | 1;
   st7789_sendcmd(dev, ST7789_COLMOD);
-  st7789_select(dev->spi, 8);
+  st7789_select(dev->spi, LCD_ST7789_SPI_BITS);
-  SPI_SEND(dev->spi, depth);
+  SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | depth);
   st7789_deselect(dev->spi);
 
   /* Cache the new BPP */
@@ -536,16 +576,52 @@ static void st7789_wrram(FAR struct st7789_dev_s *dev,
                          size_t count)
 {
   size_t i;
+#ifdef CONFIG_LCD_ST7789_3WIRE
+  size_t j;
+#endif
 
   st7789_sendcmd(dev, ST7789_RAMWR);
 
-  st7789_select(dev->spi, ST7789_BYTESPP * 8);
+#ifdef CONFIG_LCD_ST7789_3WIRE
+  if (count == 1)
+    {
+      /* We cannot send the entire buffer at once, split it to
+       * separate rows.
+       */
+
+      count = ST7789_YRES;
+      size = ST7789_XRES * ST7789_BYTESPP;
+    }
+
+  st7789_select(dev->spi, LCD_ST7789_SPI_BITS);
+
+  /* For each row */
+
+  for (i = 0; i < count; i++)
+    {
+      /* Copy data to rowbuff and add 9th bit */
+
+      for (j = 0; j < ST7789_XRES * ST7789_BYTESPP; j += 2)
+        {
+          /* Take care of correct byte order. */
+
+          rowbuff[j] = LCD_ST7789_DATA_PREFIX |
+                       (uint16_t)buff[j + 1 + (i * (size + skip))];
+          rowbuff[j + 1] = LCD_ST7789_DATA_PREFIX |
+                           (uint16_t)buff[j + (i * (size + skip))];
+        }
+
+      SPI_SNDBLOCK(dev->spi, rowbuff, size);
+    }
+#else
+  st7789_select(dev->spi, ST7789_BYTESPP * LCD_ST7789_SPI_BITS);
 
   for (i = 0; i < count; i++)
     {
       SPI_SNDBLOCK(dev->spi, buff + (i * (size + skip)),
                    size / ST7789_BYTESPP);
     }
+#endif
 
   st7789_deselect(dev->spi);
 }
@@ -585,12 +661,22 @@ static void st7789_fill(FAR struct st7789_dev_s *dev, uint16_t color)
   st7789_setarea(dev, 0, 0, ST7789_XRES - 1, ST7789_YRES - 1);
 
   st7789_sendcmd(dev, ST7789_RAMWR);
-  st7789_select(dev->spi, ST7789_BYTESPP *8);
+#ifdef CONFIG_LCD_ST7789_3WIRE
+  st7789_select(dev->spi, LCD_ST7789_SPI_BITS);
+
+  for (i = 0; i < ST7789_XRES * ST7789_YRES; i++)
+    {
+      SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | (color & 0xff));
+      SPI_SEND(dev->spi, LCD_ST7789_DATA_PREFIX | (color & 0xff00) >> 8);
+    }
+#else
+  st7789_select(dev->spi, ST7789_BYTESPP * LCD_ST7789_SPI_BITS);
 
   for (i = 0; i < ST7789_XRES * ST7789_YRES; i++)
     {
       SPI_SEND(dev->spi, color);
     }
+#endif
 
   st7789_deselect(dev->spi);
 }