lot of work connecting SD I/O with FAT lib, FAT improvements.

lib/blockdev.h

@@ -0,0 +1,54 @@
+#pragma once
+
+//
+// Block device interface, somewhat akin to stream.h
+// Used for filesystem implementations.
+//
+
+#include <stdint.h>
+
+/** Abstract block device interface
+ *
+ * Populate an instance of this with pointers to your I/O functions.
+ */
+typedef struct
+{
+	/** Sequential read at cursor
+	 * @param dest destination memory structure
+	 * @param len  number of bytes to load and store in {dest}
+	 */
+	void (*load)(void* dest, const uint16_t len);
+
+
+	/** Sequential write at cursor
+	 * @param src source memory structure
+	 * @param len number of bytes to write
+	 */
+	void (*store)(const void* src, const uint16_t len);
+
+
+	/** Write one byte at cursor
+	 * @param b byte to write
+	 */
+	void (*write)(const uint8_t b);
+
+
+	/** Read one byte at cursor
+	 * @return the read byte
+	 */
+	uint8_t (*read)(void);
+
+
+	/** Absolute seek - set cursor
+	 * @param addr new cursor address
+	 */
+	void (*seek)(const uint32_t addr);
+
+
+	/** Relative seek - move cursor
+	 * @param offset cursor address change
+	 */
+	void (*rseek)(const int16_t offset);
+
+} BLOCKDEV;
+

lib/fat16.c

@@ -103,7 +103,10 @@ uint32_t find_bs(const BLOCKDEV* dev)
 			// Verify that the boot sector has a valid signature mark
 			dev->seek(tmp + 510);
 			dev->load(&tmp2, 2);
-			if (tmp2 != 0xAA55) continue; // continue to next entry
+			if (tmp2 != 0xAA55)
+			{
+				continue; // continue to next entry
+			}
 
 			// return absolute MBR address
 			return tmp;
@@ -439,9 +442,12 @@ void write_file_header(FAT16_FILE* file, const char* fname_raw, const uint8_t at
 // =============== PUBLIC FUNCTION IMPLEMENTATIONS =================
 
 /** Initialize a FAT16 handle */
-void fat16_init(const BLOCKDEV* dev, FAT16* fat)
+bool fat16_init(const BLOCKDEV* dev, FAT16* fat)
 {
 	const uint32_t bs_a = find_bs(dev);
+
+	if (bs_a == 0) return false;
+
 	fat->dev = dev;
 	read_bs(dev, &(fat->bs), bs_a);
 	fat->fat_addr = bs_a + (fat->bs.reserved_sectors * 512);
@@ -449,6 +455,8 @@ void fat16_init(const BLOCKDEV* dev, FAT16* fat)
 	fat->data_addr = fat->rd_addr + (fat->bs.root_entries * 32); // entry is 32B long
 
 	fat->bs.bytes_per_cluster = (fat->bs.sectors_per_cluster * 512);
+
+	return true;
 }
 
 
@@ -522,13 +530,19 @@ bool fat16_is_regular(const FAT16_FILE* file)
 
 #define MIN(a, b) (((a) < (b)) ? (a) : (b))
 
-bool fat16_read(FAT16_FILE* file, void* target, uint32_t len)
+uint16_t fat16_read(FAT16_FILE* file, void* target, uint16_t len)
 {
 	if (file->cur_abs == 0xFFFF)
-		return false; // file at the end already
+		return 0; // file at the end already
 
 	if (file->cur_rel + len > file->size)
-		return false; // Attempt to read more than what is available
+	{
+		if (file->cur_rel > file->size) return 0;
+		len = file->size - file->cur_rel;
+		//return false; // Attempt to read more than what is available
+	}
+
+	const uint16_t len_orig = len;
 
 	const FAT16* fat = file->fat;
 	const BLOCKDEV* dev = fat->dev;
@@ -562,7 +576,7 @@ bool fat16_read(FAT16_FILE* file, void* target, uint32_t len)
 		len -= chunk;
 	}
 
-	return true;
+	return len_orig;
 }
 
 
@@ -1000,6 +1014,23 @@ char* fat16_rawname(const char* disp_in, char* raw_out)
 }
 
 
+FSAVEPOS fat16_savepos(const FAT16_FILE* file)
+{
+	FSAVEPOS fsp;
+	fsp.clu = file->clu;
+	fsp.num = file->num;
+	fsp.cur_rel = file->cur_rel;
+	return fsp;
+}
+
+
+void fat16_reopen(FAT16_FILE* file, const FSAVEPOS* pos)
+{
+	open_file(file->fat, file, pos->clu, pos->num);
+	fat16_seek(file, pos->cur_rel);
+}
+
+
 /** Write new file size (also to the disk). Does not allocate clusters. */
 void fat16_resize(FAT16_FILE* file, uint32_t size)
 {
@@ -1073,11 +1104,7 @@ bool fat16_rmdir(FAT16_FILE* file)
 	if (file->type != FT_SUBDIR)
 		return false; // not a subdirectory entry
 
-	const FAT16* fat = file->fat;
-
-	const uint16_t clu1 = file->clu;
-	const uint16_t num1 = file->num;
-
+	const FSAVEPOS orig = fat16_savepos(file);
 
 	// Open the subdir
 	if (!fat16_opendir(file))
@@ -1097,7 +1124,7 @@ bool fat16_rmdir(FAT16_FILE* file)
 		{
 			// Valid child file was found, aborting.
 			// reopen original file
-			open_file(fat, file, clu1, num1);
+			fat16_reopen(file, &orig);
 			return false;
 		}
 
@@ -1106,7 +1133,7 @@ bool fat16_rmdir(FAT16_FILE* file)
 	while (fat16_next(file));
 
 	// reopen original file
-	open_file(fat, file, clu1, num1);
+	fat16_reopen(file, &orig);
 
 	// and delete as ordinary file
 	delete_file_do(file);
@@ -1126,8 +1153,7 @@ bool fat16_delete(FAT16_FILE* file)
 		case FT_SUBDIR:; // semicolon needed to allow declaration after "case"
 
 			// store original file location
-			const uint16_t clu1 = file->clu;
-			const uint16_t num1 = file->num;
+			const FSAVEPOS orig = fat16_savepos(file);
 
 			// open the directory (skip "." and "..")
 			open_file(file->fat, file, file->clu_start, 2);
@@ -1139,14 +1165,14 @@ bool fat16_delete(FAT16_FILE* file)
 				{
 					// failure
 					// reopen original file
-					open_file(file->fat, file, clu1, num1);
+					fat16_reopen(file, &orig);
 					return false;
 				}
 			}
 			while (fat16_next(file));
 
 			// go up and delete the dir
-			open_file(file->fat, file, clu1, num1);
+			fat16_reopen(file, &orig);
 			return fat16_rmdir(file);
 
 		default:
@@ -1158,11 +1184,9 @@ bool fat16_delete(FAT16_FILE* file)
 
 bool fat16_parent(FAT16_FILE* file)
 {
-	const uint16_t clu1 = file->clu;
-	const uint16_t num1 = file->num;
-
 	// open second entry of the directory
 	open_file(file->fat, file, file->clu, 1);
+	const FSAVEPOS orig = fat16_savepos(file);
 
 	// if it's a valid PARENT link, follow it.
 	if (file->type == FT_PARENT)
@@ -1174,7 +1198,7 @@ bool fat16_parent(FAT16_FILE* file)
 	{
 		// in root already?
 		// reopen original file
-		open_file(file->fat, file, clu1, num1);
+		fat16_reopen(file, &orig);
 		return false;
 	}
 }

lib/fat16.h

@@ -10,26 +10,7 @@
 #include <stdint.h>
 #include <stdbool.h>
 
-/**
- * Abstract block device interface
- *
- * Populate this with pointers to your I/O functions.
- */
-typedef struct
-{
-	// Sequential read
-	void (*load)(void* dest, const uint16_t len);
-	// Sequential write
-	void (*store)(const void* src, const uint16_t len);
-	// Sequential byte write
-	void (*write)(const uint8_t b);
-	// Sequential byte read
-	uint8_t (*read)(void);
-	// Absolute seek
-	void (*seek)(const uint32_t);
-	// Relative seek
-	void (*rseek)(const int16_t);
-} BLOCKDEV;
+#include "blockdev.h"
 
 
 // -------------------------------
@@ -52,6 +33,15 @@ typedef enum
 } FAT16_FT;
 
 
+/** "File address" for saving and restoring file */
+typedef struct
+{
+	uint16_t clu;
+	uint16_t num;
+	uint32_t cur_rel;
+} FSAVEPOS;
+
+
 // Include definitions of fully internal structs
 #include "fat16_internal.h"
 
@@ -111,9 +101,22 @@ typedef struct __attribute__((packed))
 }
 FAT16_FILE;
 
+/**
+ * Save a file "position" into a struct, for later restoration.
+ * Cursor is also saved.
+ */
+FSAVEPOS fat16_savepos(const FAT16_FILE* file);
 
-/** Initialize the file system - store into "fat" */
-void fat16_init(const BLOCKDEV* dev, FAT16* fat);
+/**
+ * Restore a file from a saved position.
+ */
+void fat16_reopen(FAT16_FILE* file, const FSAVEPOS* pos);
+
+
+/**
+ * Initialize the file system - store into "fat"
+ */
+bool fat16_init(const BLOCKDEV* dev, FAT16* fat);
 
 
 /**
@@ -127,6 +130,9 @@ void fat16_root(const FAT16* fat, FAT16_FILE* file);
 /**
  * Resolve the disk label.
  * That can be in the Boot Sector, or in the first root directory entry.
+ *
+ * @param fat       the FAT handle
+ * @param label_out string to store the label in. Should have at least 12 bytes.
  */
 char* fat16_disk_label(const FAT16* fat, char* label_out);
 
@@ -143,9 +149,9 @@ bool fat16_seek(FAT16_FILE* file, uint32_t addr);
 
 /**
  * Read bytes from file into memory
- * Returns false on I/O error (bad file, out of range...)
+ * Returns number of bytes read, 0 on error.
  */
-bool fat16_read(FAT16_FILE* file, void* target, uint32_t len);
+uint16_t fat16_read(FAT16_FILE* file, void* target, uint16_t len);
 
 
 /**

lib/fat16_internal.h

@@ -9,7 +9,6 @@
 /** Boot Sector structure */
 typedef struct __attribute__((packed))
 {
-
 	// Fields loaded directly from disk:
 
 	// 13 bytes skipped

lib/sd.c

@@ -1,5 +1,4 @@
 #include <avr/io.h>
-#include <avr/pgmspace.h>
 #include <util/delay.h>
 #include <stdint.h>
 #include <stdbool.h>
@@ -15,8 +14,13 @@
 #define SD_WRITE_BLOCK 0x58 // write single block
 
 
+bool sd_inited = false;
+
 bool sd_init()
 {
+	if (sd_inited) return true;
+	sd_inited = true;
+
 	uint8_t i;
 	spi_init();
 

lib/sd.h

@@ -29,7 +29,7 @@ bool sd_init();
  * @param arg command argument
  * @return return value on success, 0xFF if nothing received back.
  */
-uint8_t sd_command(const uint8_t cmd, const uint32_t arg);
+uint8_t sd_command(uint8_t cmd, uint32_t arg);
 
 
 /**
@@ -42,7 +42,7 @@ uint8_t sd_command(const uint8_t cmd, const uint32_t arg);
  * @param len      number of bytes to read
  * @return true on success
  */
-bool sd_read(const uint32_t sector, const uint16_t read_at, uint8_t * buffer, const uint16_t write_at, const uint16_t len);
+bool sd_read(uint32_t sector, uint16_t read_at, uint8_t * buffer, uint16_t write_at, uint16_t len);
 
 
 /**
@@ -52,4 +52,4 @@ bool sd_read(const uint32_t sector, const uint16_t read_at, uint8_t * buffer, co
  * @param buffer512 source buffer
  * @return true on success
  */
-bool sd_write(const uint32_t sector, const uint8_t * buffer512);
+bool sd_write(uint32_t sector, const uint8_t * buffer512);

lib/sd_blockdev.c

@@ -0,0 +1,172 @@
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "sd_blockdev.h"
+#include "sd.h"
+
+// helpers
+void load_sector(const uint32_t addr);
+void store_sector();
+void handle_cursor_ov();
+
+// blockdev methods
+void dev_load(void* dest, const uint16_t len);
+void dev_store(const void* src, const uint16_t len);
+uint8_t dev_read();
+void dev_write(const uint8_t b);
+void dev_seek(const uint32_t addr);
+void dev_rseek(const int16_t offset);
+
+
+/** Sector buffer */
+uint8_t buff[512];
+
+/** Address of the buffered sector */
+uint32_t buff_addr;
+
+/** Buffer needs to be flushed before next read */
+bool buff_dirty = false;
+
+/** Buffer holds a valid sector */
+bool buff_valid = false;
+
+/** seek cursor */
+uint32_t cursor_sec;
+uint16_t cursor_offs;
+
+
+/** Flush the buffer, if it's dirty */
+void sdb_flush()
+{
+	if (buff_dirty)
+	{
+		store_sector();
+		buff_dirty = false;
+	}
+}
+
+
+void load_sector(const uint32_t addr)
+{
+	// do not load if already loaded
+	if (buff_valid && buff_addr == addr) {
+		return;
+	}
+
+	sdb_flush();
+
+	// read entire sector
+	sd_read(addr, 0, buff, 0, 512);
+	buff_valid = true;
+	buff_addr = addr;
+}
+
+
+void store_sector()
+{
+	// Do not store if not laoded.
+	if (!buff_dirty) return;
+	if (!buff_valid) return;
+
+	sd_write(buff_addr, buff);
+}
+
+
+/**
+ * Handle cursor overflow.
+ * MUST ABSOLUTELY NOT load/store buffer or change buffer addr!
+*/
+inline void handle_cursor_ov()
+{
+	if (cursor_offs >= 512)
+	{
+		cursor_sec++;
+		cursor_offs = 0;
+	}
+}
+
+
+
+void dev_write(const uint8_t b)
+{
+	load_sector(cursor_sec);
+	buff[cursor_offs++] = b;
+	buff_dirty = true;
+
+	handle_cursor_ov();
+}
+
+
+uint8_t dev_read()
+{
+	load_sector(cursor_sec);
+	const uint8_t b = buff[cursor_offs++];
+
+	handle_cursor_ov();
+
+	return b;
+}
+
+
+void dev_load(void* dest, const uint16_t len)
+{
+	for (uint16_t a = 0; a < len; a++)
+	{
+		*((uint8_t*)dest++) = dev_read();
+	}
+}
+
+
+void dev_store(const void* src, const uint16_t len)
+{
+	for (uint16_t a = 0; a < len; a++)
+	{
+		dev_write(*((uint8_t*)src++));
+	}
+}
+
+
+void dev_seek(const uint32_t addr)
+{
+	// compute sector and offset counters
+	cursor_sec = addr >> 9;
+	cursor_offs = addr & 0x1FF;
+}
+
+
+void dev_rseek(const int16_t offset)
+{
+	// add WITHIN the same sector
+	if (offset > 0 && cursor_offs + offset < 512)
+	{
+		cursor_offs += offset;
+		return;
+	}
+
+	// subtract WITHIN the same sector
+	if (offset < 0 && ((uint16_t)(-offset) <= cursor_offs))
+	{
+		cursor_offs += offset;
+		return;
+	}
+
+	// abs addr change
+	dev_seek(((cursor_sec << 9) + cursor_offs) + offset);
+}
+
+
+/** Init SD card block device */
+bool sdb_init(BLOCKDEV* dev)
+{
+	if(!sd_init()) return false;
+
+	dev->load = &dev_load;
+	dev->store = &dev_store;
+	dev->read = &dev_read;
+	dev->write = &dev_write;
+	dev->seek = &dev_seek;
+	dev->rseek = &dev_rseek;
+
+	return true;
+}
+

lib/sd_blockdev.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include "blockdev.h"
+
+/**
+ * Flush the sector buffer if it's dirty.
+ *
+ * Should be called after each sequence of writes,
+ * to avoid data loss.
+ */
+void sdb_flush();
+
+/** Initialize the SD card block device */
+bool sdb_init(BLOCKDEV* dev);

lib/sd_fat.c

@@ -0,0 +1,34 @@
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "sd_blockdev.h"
+#include "sd_fat.h"
+#include "fat16.h"
+
+FAT16 _fat;
+BLOCKDEV _dev;
+
+bool sdfat_inited = false;
+
+bool sdfat_init()
+{
+	if (sdfat_inited) return true;
+	sdfat_inited = true;
+
+	if (!sdb_init(&_dev)) return false;
+	if (!fat16_init(&_dev, &_fat)) return false;
+
+	return true;
+}
+
+
+void sdfat_root(FAT16_FILE* file)
+{
+	fat16_root(&_fat, file);
+}
+
+
+void sdfat_disk_label(char* str)
+{
+	fat16_disk_label(&_fat, str);
+}

lib/sd_fat.h

@@ -0,0 +1,19 @@
+#pragma once
+
+//
+// FAT-on-SD helpers
+//
+
+#include "fat16.h"
+
+/** Initialize FAT16 filesystem on a SPI-connected SD card */
+bool sdfat_init();
+
+/** Get first file of the root folder. */
+void sdfat_root(FAT16_FILE* file);
+
+/** Get a disk label. Str should have 12 chars. */
+void sdfat_disk_label(char* str);
+
+/** Flush the SD buffer (alis of sdb_flush()) */
+#define sdfat_flush() sdb_flush()

lib/spi.c

@@ -5,9 +5,14 @@
 #include "iopins.h"
 #include "spi.h"
 
+bool spi_inited = false;
+
 /** Init SPI (for SD card communication) */
 void spi_init()
 {
+	if (spi_inited) return;
+	spi_inited = true;
+
 	// Pin configuration
 	as_output(PIN_SS);
 	as_output(PIN_MOSI);
@@ -20,7 +25,7 @@ void spi_init()
 
 
 /** Write a byte to SPI. Returns received byte. */
-uint8_t spi_write(const uint8_t b)
+uint8_t spi_write(uint8_t b)
 {
 	SPDR = b;
 	while (!(SPSR & _BV(SPIF)));

lib/spi.h

@@ -26,5 +26,5 @@ void spi_init();
  * @param ch the written byte
  * @return received byte
  */
-uint8_t spi_write(const uint8_t b);
+uint8_t spi_write(uint8_t b);
 

lib/stream.c

@@ -6,7 +6,7 @@
 #include "calc.h"
 
 
-static char tmpstr[12]; // buffer for number rendering
+static char tmpstr[16]; // buffer for number rendering
 
 
 void put_bytes(const STREAM *p, const uint8_t* str, const uint16_t len)

lib/uart.c

@@ -11,7 +11,7 @@
 
 // Shared stream instance
 static STREAM _uart_singleton;
-STREAM* uart;
+STREAM* uart = &_uart_singleton;
 
 
 void _uart_init_do(uint16_t ubrr)
@@ -28,8 +28,6 @@ void _uart_init_do(uint16_t ubrr)
 
 	_uart_singleton.tx = &uart_tx;
 	_uart_singleton.rx = &uart_rx;
-
-	uart = &_uart_singleton;
 }