[lcd] add support for operating on virtual framebuffers

Current implementation contains full support for:
- transparent switching between direct and framebuffer rendering modes
- writing characters to framebuffers
- loading frame from memory to physical display

As well as partial support for instruction writes including:
- resetting the display (clears memory, sets cursor at 0:0, switches to increment mode)
- switching between increment/decrement modes
- setting cursor position

Core/Src/lcd.c

@@ -2,22 +2,45 @@
 #include "lcd.h"
 #include "generic_macros.h"
 
+static char display_framebuffer[16*2*DISPLAY_FRAMES_AVAILABLE];
+size_t display_current_frame;
+static size_t display_framebuffer_mode;
+
+static struct Display_emu_state des;
+
 void display_init(void)
 {
+	// prepare virtual framebuffer
+	display_current_frame = 0;
+	display_framebuffer_mode = 0;
+	des.cursor_offset = 0;
+	des.next = 0;
+	memset(display_framebuffer, 0x20, 16*2*DISPLAY_FRAMES_AVAILABLE);
+
 	// switch to 4-bit 2-line mode
-	  display_write_instruction_byte(0x28);
+	display_write_instruction_byte(0x28);
 
-	  // clear display
-	  display_write_instruction_byte(0x01);
+	// clear display
+	display_write_instruction_byte(0x01);
 
-	  // enable display
-	  display_write_instruction_byte(0x0C);
+	// enable display
+	display_write_instruction_byte(0x0C);
 
-	  // move cursor to first line
-	  display_write_instruction_byte(0x80);
+	// move cursor to first line
+	display_write_instruction_byte(0x80);
 }
 
-uint8_t display_read_status(void)
+void display_to_framebuffer(void)
+{
+	display_framebuffer_mode = 1;
+}
+
+void display_to_direct(void)
+{
+	display_framebuffer_mode = 0;
+}
+
+static uint8_t display_read_status(void)
 {
 	// make sure GPIOE is in correct mode
 	GPIOE->MODER = 0x00504000;
@@ -43,7 +66,7 @@ uint8_t display_read_status(void)
 	return status;
 }
 
-void display_write_instruction_byte(uint8_t code)
+static void display_write_instruction_byte_direct(uint8_t code)
 {
 	DISPLAY_POLL_UNTIL_READY;
 
@@ -62,7 +85,37 @@ void display_write_instruction_byte(uint8_t code)
 	GPIOE->BSRR = (DISPLAY_ENA << 16);
 }
 
-void display_write_data_byte(uint8_t code)
+static void display_write_instruction_byte_framebuffer(uint8_t code)
+{
+	// emulate physical display behavior on receiving instructions
+	if (code & 0x80) {
+		// decode new cursor offset
+		size_t offset = ((code & 0x40) >> 2) | (code & 0xF);
+		des.cursor_offset = offset;
+	} else if (code == 0x01) {
+		// reset screen
+		memset(&(display_framebuffer[16*2*display_current_frame]), 0x20, 16*2);
+		des.cursor_offset = 0;
+		des.next = 0;
+	} else if (code == 0x06) {
+		// set increment mode
+		des.next = 0;
+	} else if (code == 0x04) {
+		// set decrement mode
+		des.next = 1;
+	}
+}
+
+void display_write_instruction_byte(uint8_t code)
+{
+	if (display_framebuffer_mode) {
+		display_write_instruction_byte_framebuffer(code);
+	} else {
+		display_write_instruction_byte_direct(code);
+	}
+}
+
+static void display_write_data_byte_direct(uint8_t code)
 {
 	DISPLAY_POLL_UNTIL_READY;
 
@@ -81,12 +134,45 @@ void display_write_data_byte(uint8_t code)
 	GPIOE->BSRR = DISPLAY_ENA << 16;
 }
 
+static void display_write_data_byte_framebuffer(uint8_t code)
+{
+	display_framebuffer[16*2*display_current_frame + des.cursor_offset] = (char) code;
+	des.cursor_offset += des.next ? -1 : 1;
+}
+
+void display_write_data_byte(uint8_t code)
+{
+	if (display_framebuffer_mode) {
+		display_write_data_byte_framebuffer(code);
+	} else {
+		display_write_data_byte_direct(code);
+	}
+}
+
 void display_write_data_seq(char *codes)
 {
 	for (size_t i = 0; i < 16; i++) {
-		if (codes[i] != 0)
+		if (codes[i])
 			display_write_data_byte(codes[i]);
 		else
 			break;
 	}
 }
+
+void display_load(uint32_t frame_no)
+{
+	if (display_framebuffer_mode)
+		return;
+
+	DISPLAY_CLEAR;
+
+	for (uint32_t i = 0; i < 16; i++) {
+		display_write_data_byte_direct(display_framebuffer[16*2*display_current_frame + i]);
+	}
+
+	DISPLAY_SET_CURSOR(1, 0);
+
+	for (uint32_t i = 0; i < 16; i++) {
+		display_write_data_byte_direct(display_framebuffer[16*2*display_current_frame + i + 16]);
+	}
+}

Core/Src/main.c

@@ -30,7 +30,6 @@
 #include "CS43L22.h"
 #include "SST25VF016B.h"
 #include "LIS302DL.h"
-#include "DHT11.h"
 #include "MP45DT02.h"
 #include "LSM9DS1.h"
 
@@ -65,6 +64,8 @@ SPI_HandleTypeDef hspi1;
 
 TIM_HandleTypeDef htim2;
 
+extern size_t display_current_frame;
+
 /* USER CODE BEGIN PV */
 
 void ((*executors[])(void)) = {
@@ -305,10 +306,30 @@ int main(void)
   GPIOD->ODR = 0xF000;
   button_init_and_test();
 
+  // perform all tests
+  display_to_framebuffer();
+
+  for (display_current_frame = 0; display_current_frame < 11; display_current_frame++)
+  {
+	  executors[display_current_frame]();
+  }
+
+  display_to_direct();
+  display_current_frame = 0;
+
+  while (1) {
+	  display_load(display_current_frame);
+	  display_current_frame++;
+	  display_current_frame %= 11;
+	  HAL_Delay(1000);
+  }
+
   /* USER CODE END 2 */
 
   /* Infinite loop */
   /* USER CODE BEGIN WHILE */
+
+  /*
   while (1)
   {
 	if (delay_between_runs[current_executor_id] == -1 && buttons_interrupt_enabled)
@@ -334,10 +355,11 @@ int main(void)
 	} else {
 		HAL_Delay(delay_between_runs[current_executor_id]);
 	}
+	*/
     /* USER CODE END WHILE */
 
     /* USER CODE BEGIN 3 */
-  }
+  //}
   /* USER CODE END 3 */
 }