Add Read/write without buffer example

#210 related

avr/libraries/Optiboot_flasher/examples/Read_write_without_buffer/Read_write_without_buffer.ino

@@ -0,0 +1,128 @@
+/***********************************************************************|
+| Optiboot Flash read/write                                             |
+|                                                                       |
+| Read_write_without_buffer.ino                                         |
+|                                                                       |
+| A library for interfacing with Optiboot Flash's write functionality   |
+| Developed in 2021 by MCUdude                                          |
+| https://github.com/MCUdude/                                           |
+|                                                                       |
+| In this low-level example we write 16-bit values to one flash page,   |
+| and 8-bit values to another page. What's different about this         |
+| example is that we do this without using a RAM buffer where the       |
+| contents are stored before writing to flash. Instead, the internal,   |
+| temporary buffer is used. By doing this we reduce RAM usage, but it   |
+| is not nearly as user friendly as using the Flash library.            |
+|                                                                       |
+| IMPORTANT THINGS:                                                     |
+| - All flash content gets erased after each upload cycle               |
+| - Allocated flash space must be page aligned (it is in this example)  |
+| - Writing to EEPROM destroys temporary buffer so make sure you call   |
+|   optiboot_page_write before reusing the buffer or using EEPROM       |
+| - You can write only once into one location of temporary buffer       |
+|***********************************************************************/
+
+
+#include <optiboot.h>
+
+// Workaround for devices that has 64kiB flash or less
+#ifndef pgm_read_byte_far
+#define pgm_read_byte_far pgm_read_byte_near
+#endif
+#ifndef pgm_get_far_address
+#define pgm_get_far_address
+#endif
+
+
+// Allocate one flash pages for storing data. If you want to allocate space in the high progmem (>64kiB)
+// You can replace PROGMEM with PROGMEM1
+#define NUMBER_OF_PAGES 2
+const uint8_t flashSpace[SPM_PAGESIZE * NUMBER_OF_PAGES] __attribute__((aligned(SPM_PAGESIZE))) PROGMEM = {};
+
+
+// Function for writing 16-bit integers to a flash page
+void flash_write_int(uint32_t base_addr, uint16_t offset_addr, int16_t data)
+{
+  // Start by erasing the flash page before we start writing to the buffer
+  if ((offset_addr & 0xFF) == 0)
+    optiboot_page_erase(base_addr + (offset_addr & 0xFF00));
+
+  // Write the 16-bit value to the buffer
+  optiboot_page_fill(base_addr + offset_addr, data);
+
+  // Write the buffer to flash when the buffer is full
+  if ((offset_addr & 0xFF) == 0xFE)
+    optiboot_page_write(base_addr + (offset_addr & 0xFF00));
+}
+
+
+// Function to write bytes to a flash page
+void flash_write_byte(uint32_t base_addr, uint16_t offset_addr, uint8_t data)
+{
+  static uint8_t low_byte = 0;
+
+  if ((offset_addr & 0xFF) == 0)
+    optiboot_page_erase(base_addr + (offset_addr & 0xFF00));
+
+  if (!(offset_addr & 0x01)) // Address is 2, 4, 6 etc.
+    low_byte = data;
+  else                       // Address is 1, 3, 5 etc.
+    optiboot_page_fill(base_addr + offset_addr, (data << 8) | low_byte);
+
+  if ((offset_addr & 0xFF) == 0xFE)
+    optiboot_page_write(base_addr + (offset_addr & 0xFF00));
+}
+
+
+// Function to force a flash page write operation
+void flash_end_write(uint32_t base_addr, uint16_t offset_addr)
+{
+  // Write the buffer to flash if there are any contents in the buffer
+  if ((offset_addr & 0xFF) != 0x00)
+    optiboot_page_write(base_addr + (offset_addr & 0xFF00));
+}
+
+
+void setup()
+{
+  delay(2000);
+  Serial.begin(9600);
+
+  static uint16_t addr = 0;
+
+  Serial.print(F("Filling up flash page 0 with 16-bit values...\n"));
+  // Fill the first flash page (page 0) with 16-bit values (0x100 to 0x01FF)
+  for(uint8_t data = 0; data < (SPM_PAGESIZE / 2); data++)
+  {
+    flash_write_int(pgm_get_far_address(flashSpace), addr, data + 0x0100); // Write data
+    addr += 2; // Increase memory address by two since we're writing 16-bit values
+  }
+  // Force an end write in case it hasn't already been done in flash_write_int
+  flash_end_write(pgm_get_far_address(flashSpace), --addr);
+
+
+  Serial.print(F("Filling up flash page 1 with 8-bit values...\n"));
+  // Fill the second flash page (page 1) with 0-bit values (0x00 to 0x0FF)
+  for(uint16_t data = 0; data < SPM_PAGESIZE; data++)
+  {
+    addr++; // Increase memory address by one since we're writing 8-bit values
+    flash_write_byte(pgm_get_far_address(flashSpace), addr, data); // Write data
+  }
+  // Force an end write in case it hasn't already been done in flash_write_byte
+  flash_end_write(pgm_get_far_address(flashSpace), addr);
+
+
+  Serial.print(F("Flash pages filled. Reading back their content.\nPage 0:\n"));
+  for(uint16_t i = 0; i < SPM_PAGESIZE; i += 2)
+    Serial.printf(F("Flash mem addr: 0x%05lx, content: 0x%04x\n"), pgm_get_far_address(flashSpace) + i, (pgm_read_byte_far(pgm_get_far_address(flashSpace) + i + 1) << 8) + (pgm_read_byte_far(pgm_get_far_address(flashSpace) + i)));
+
+  Serial.println(F("\n\nPage 1:"));
+  for(uint16_t i = 0; i < SPM_PAGESIZE; i++)
+    Serial.printf(F("Flash mem addr: 0x%05lx, content: 0x%02x\n"), pgm_get_far_address(flashSpace) + SPM_PAGESIZE + i, pgm_read_byte_far(pgm_get_far_address(flashSpace) + SPM_PAGESIZE + i));
+}
+
+
+void loop()
+{
+
+}