Add lcddrvce example for half-res mode

Author: calc84maniac

examples/library_examples/lcddrvce/half_res/.gitignore

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+obj/
+bin/
+src/gfx/*.c
+src/gfx/*.h
+src/gfx/*.8xv
+.DS_Store
+convimg.yaml.lst

examples/library_examples/lcddrvce/half_res/makefile

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+# ----------------------------
+# Makefile Options
+# ----------------------------
+
+NAME = DEMO
+ICON = icon.png
+DESCRIPTION = "CE C Toolchain Demo"
+COMPRESSED = NO
+
+CFLAGS = -Wall -Wextra -Oz
+CXXFLAGS = -Wall -Wextra -Oz
+
+# ----------------------------
+
+include $(shell cedev-config --makefile)

examples/library_examples/lcddrvce/half_res/src/main.c

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+#include <lcddrvce.h>
+#include <graphx.h>
+#include <sys/lcd.h>
+#include <ti/getcsc.h>
+#include <stdint.h>
+#include <string.h>
+
+#define HALF_LCD_WIDTH (LCD_WIDTH / 2)
+#define HALF_LCD_HEIGHT (LCD_HEIGHT / 2)
+
+/* Function Prototypes */
+void PrintCentered(const char *str, unsigned int border);
+void QuarterResFillScreen(uint8_t color);
+void QuarterResSwapDraw(void);
+void SetHalfResMode(bool enable);
+
+int main(void)
+{
+    /* Initialize GraphX first, because it sets LCD timing */
+    gfx_Begin();
+    
+    /* Set half-resolution mode */
+    SetHalfResMode(true);
+
+    /* Set clipping to an 160x120 area that draws to every second line of the half-res buffer */
+    gfx_SetClipRegion(0, 0, HALF_LCD_WIDTH - 1, HALF_LCD_HEIGHT - 1);
+    gfx_SetDrawBuffer();
+
+    unsigned int border = 2;
+    int dir = 1;
+
+    /* Wait for a keypress */
+    while (!os_GetCSC())
+    {
+        /* Clear the screen, gfx_FillScreen covers too much area so use this instead */
+        QuarterResFillScreen(255);
+        
+        /* Print the message on the screen */
+        PrintCentered("Hello, World!", border);
+
+        /* Swap buffers and fill in every second line */
+        QuarterResSwapDraw();
+
+        /* Change the border size for the next frame */
+        border += dir;
+        if (border <= 2 || border >= 25)
+        {
+            dir = -dir;
+        }
+    }
+
+    /* Ensure one empty frame is fully displayed to make the transition to full-res clean */
+    gfx_FillScreen(255);
+    gfx_SwapDraw();
+    gfx_FillScreen(255);
+    gfx_SwapDraw();
+
+    /* Restore normal resolution mode */
+    SetHalfResMode(false);
+
+    /* Wait for the second empty frame to display */
+    gfx_Wait();
+
+    /* Deinitialize GraphX */
+    gfx_End();
+
+    return 0;
+}
+
+/* Prints a quarter-res screen centered string */
+void PrintCentered(const char *str, unsigned int border)
+{
+    unsigned int width = gfx_GetStringWidth(str);
+    gfx_PrintStringXY(str,
+                      (HALF_LCD_WIDTH - width) / 2,
+                      (HALF_LCD_HEIGHT - 8) / 2);
+    gfx_Circle(HALF_LCD_WIDTH / 2, HALF_LCD_HEIGHT / 2, width / 2 + border);
+}
+
+/* Fills the drawable area of a quarter-res screen */
+void QuarterResFillScreen(uint8_t color)
+{
+    uint8_t oldColor = gfx_SetColor(color);
+    gfx_FillRectangle_NoClip(0, 0, HALF_LCD_WIDTH, HALF_LCD_HEIGHT);
+    gfx_SetColor(oldColor);
+}
+
+/* Copies the rendered lines to the unrendered lines before swapping the buffer */
+void QuarterResSwapDraw(void)
+{
+    gfx_CopyRectangle(gfx_buffer, gfx_buffer, 0, 0, HALF_LCD_WIDTH, 0, HALF_LCD_WIDTH, HALF_LCD_HEIGHT);
+    gfx_SwapDraw();
+}
+
+void SetHalfResMode(bool enable)
+{
+    typedef struct lcd_timing
+    {
+        uint32_t : 2;
+        uint32_t PPL : 6;
+        uint32_t HSW : 8;
+        uint32_t HFP : 8;
+        uint32_t HBP : 8;
+
+        uint32_t LPP : 10;
+        uint32_t VSW : 6;
+        uint32_t VFP : 8;
+        uint32_t VBP : 8;
+
+        uint32_t PCD_LO : 5;
+        uint32_t CLKSEL : 1;
+        uint32_t ACB : 5;
+        uint32_t IVS : 1;
+        uint32_t IHS : 1;
+        uint32_t IPC : 1;
+        uint32_t IOE : 1;
+        uint32_t : 1;
+        uint32_t CPL : 10;
+        uint32_t BCD : 1;
+        uint32_t PCD_HI : 5;
+    } lcd_timing_t;
+
+    typedef struct res_settings
+    {
+        uint8_t frctrl2;
+        uint8_t bpa;
+        uint16_t xe;
+        uint8_t tfa;
+        uint8_t ramctrl1;
+        lcd_timing_t timing;
+    } res_settings_t;
+
+    static res_settings_t settings[2] =
+    {
+        {
+            /* Default ST7789 settings */
+            .frctrl2 = LCD_FRCTRL2_DEFAULT,
+            .bpa = LCD_BPA_DEFAULT,
+            .xe = LCD_WIDTH - 1,
+            .tfa = 0,
+            .ramctrl1 = LCD_RAMCTRL1_DEFAULT
+        },
+        {
+            /* With the following ST7789 timing:
+             * Refreshes LCD in at most 16.51 ms after VSYNC, assuming worst case 9.5 MHz clock
+             * Waits at least 3.42 ms after VSYNC to read LCD memory, assuming worst case 10.5 MHz clock
+             */
+            .frctrl2 = 8, /* 378 clocks per line */
+            .bpa = 95,    /* 95 lines of back porch */
+            .xe = HALF_LCD_WIDTH - 1,
+            .tfa = HALF_LCD_WIDTH,
+            .ramctrl1 = LCD_RAM_RGB | LCD_DM_VSYNC,
+            /* With the following PL111 timing:
+             * Refreshes LCD at 60 Hz = 24 MHz / (800*250*2), a VSYNC period of 16.67 ms
+             * Outputs 38400 pixels to LCD memory within the first 3.40 ms after VSYNC
+             */
+            .timing =
+            {
+                .PPL = 768 / 16 - 1, /* 768 pixels per line */
+                .HSW = 1 - 1,
+                .HFP = (800 - 768 - 1 - 1) - 1, /* 800 total clocks per line */
+                .HBP = 1 - 1,
+                .LPP = HALF_LCD_WIDTH * LCD_HEIGHT / 768, /* 50 lines */
+                .VSW = 1 - 1,
+                .VFP = 250 - (HALF_LCD_WIDTH * LCD_HEIGHT / 768) - 1, /* 250 total lines */
+                .VBP = 0,
+                .PCD_LO = (2 - 2) & 0x1F, /* clock divisor of 2 */
+                .CLKSEL = 0,
+                .ACB = 0,
+                .IVS = 1,
+                .IHS = 1,
+                .IPC = 1,
+                .IOE = 1,
+                .CPL = 768 - 1,
+                .BCD = 0,
+                .PCD_HI = (2 - 2) >> 5
+            }
+        }
+    };
+
+    const res_settings_t *p = &settings[enable];
+
+    /* Initialize LCD driver */
+    lcd_Init();
+
+    /* Set clocks per line */
+    lcd_SetNormalFrameRateControl(p->frctrl2);
+    /* Set back porch */
+    lcd_SendCommand1(LCD_CMD_PORCTRL, p->bpa);
+    /* Set horizontal output window */
+    lcd_SetColumnAddress(0, p->xe);
+    /* Set fixed left scroll area */
+    lcd_SetScrollArea(p->tfa, LCD_WIDTH - p->tfa, 0);
+    /* Set starting vertical scroll address to 0 */
+    lcd_SetScrollAddress(0);    
+    /* Set display mode */
+    lcd_SetRamInterface(p->ramctrl1);
+    /* Set interlace mode */
+    lcd_SetInterlacedMode(enable);
+
+    /* Save old display timing when enabling */
+    if (enable)
+    {
+        memcpy(&settings[0].timing, (const void *)&lcd_Timing0, sizeof(settings[0].timing));
+    }
+    /* Set display timing */
+    memcpy((void *)&lcd_Timing0, &p->timing, sizeof(p->timing));
+
+    /* Cleanup LCD driver */
+    lcd_Cleanup();
+}