To use the RAM disk driver, two files, in addition to the generic FS files, must be included in the build:
fs_dev_ramdisk.c.fs_dev_ramdisk.h.
The file fs_dev_ramdisk.h must also be #included in any application or header files that directly reference the driver (for example, by registering the device driver). The following directory must be on the project include path:
\Micrium\Software\uC-FS\Dev\RAMDisk
A single RAM disk is opened as shown in Listing - Opening a RAM disk volume. The file system initialization (FS_Init()) function must have previously been called.
ROM/RAM characteristics and performance benchmarks of the RAM disk driver can be found in section 11-1-1 “Driver Characterization” Driver Characterization. For more information about the FS_DEV_RAM_CFG structure, see section D-4 “FSFS_DEV_RAM_CFG”.CFG.
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#define APP_CFG_FS_RAM_SEC_SIZE 512 (1)
#define APP_CFG_FS_RAM_NBR_SECS (48 * 1024)
static CPU_INT32U App_FS_RAM_Disk[APP_CFG_FS_RAM_SEC_SIZE * APP_CFG_FS_RAM_NBR_SECS / 4];
CPU_BOOLEAN App_FS_AddRAM (void)
{
FS_ERR err;
FS_DEV_RAM_CFG cfg;
FS_DevDrvAdd((FS_DEV_API *)&FSDev_RAM, (2)
(FS_ERR *)&err);
if ((err != FS_ERR_NONE) && (err != FS_ERR_DEV_DRV_ALREADY_ADDED)) {
return (DEF_FAIL);
}
ram_cfg.SecSize = APP_CFG_FS_RAM_SEC_SIZE; (3)
ram_cfg.Size = APP_CFG_FS_RAM_NBR_SECS;
ram_cfg.DiskPtr = (void *)&App_FS_RAM_Disk[0];
(4)
FSDev_Open((CPU_CHAR *)"ram:0:", (a)
(void *)&ram_cfg, (b)
(FS_ERR *)&err);
if (err != FS_ERR_NONE) {
return (DEF_FAIL);
}
(5)
FSVol_Open((CPU_CHAR *)"ram:0:", (a)
(CPU_CHAR *)"ram:0:", (b)
(FS_PARTITION_NBR ) 0, (c)
(FS_ERR *)&err);
switch (err) {
case FS_ERR_NONE:
APP_TRACE_DBG((" ...opened volume (mounted).\r\n"));
break;
case FS_ERR_PARTITION_NOT_FOUND: /* Volume error. */
APP_TRACE_DBG((" ...opened device (not formatted).\r\n"));
FSVol_Fmt("ram:0:", (void *)0, &err); (6)
if (err != FS_ERR_NONE) {
APP_TRACE_DBG((" ...format failed.\r\n"));
return (DEF_FAIL);
}
break;
default: /* Device error. */
APP_TRACE_DBG((" ...opening volume failed w/err = %d.\r\n\r\n", err));
return (DEF_FAIL);
}
return (DEF_OK);
} |
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(1) The sector size and number of sectors in the RAM disk must be defined. The sector size should be 512, 1024, 2048 or 4096; the number of sectors will be determined by your application requirements. This defines a 24-MB RAM disk (49152 512-B sectors). On most CPUs, it is beneficial to 32-bit align the RAM disk, since this will speed up access. |
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(2) Register the RAM disk driver |
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(3) The RAM disk parameters—sector size, size (in sectors) and pointer to the disk—should be assigned to a |
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(4) |
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4a) and a pointer to a device driver-specific configuration structure ( |
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4b). The device name ( |
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4a) |
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is composed of a device driver name (“ram”), a single colon, an ASCII-formatted integer (the unit number) and another colon. |
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(5) |
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(6) |
If the RAM disk initialization succeeds, the file system will produce the trace output as shown in in Figure 13 - 1RAM disk initialization trace output (if a sufficiently high trace level is configured). See section E-9 “Trace Configuration” Trace Configuration about configuring the trace level.
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