「App:Library:LVGL:docs:Overview:File system」の版間の差分

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LVGL has a 'File system' abstraction module that enables you to attach any type of file system. A file system is identified by an assigned drive letter. For example, if an SD card is associated with the letter <code style="color: #bb0000;">'S'</code>, a file can be reached using <code style="color: #bb0000;">"S:path/to/file.txt"</code>.
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LVGL has a 'File system' abstraction module that enables you to attach any type of file system.  
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A file system is identified by an assigned drive letter.  
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 +
For example, if an SD card is associated with the letter <code style="color: #bb0000;">'S'</code>, a file can be reached using <code style="color: #bb0000;">"S:path/to/file.txt"</code>.
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|LVGL has a 'File system' abstraction module that enables you to attach any type of file system.
 +
 
 +
A file system is identified by an assigned drive letter.
 +
 
 +
For example, if an SD card is associated with the letter <code style="color: #bb0000;">'S'</code>, a file can be reached using <code style="color: #bb0000;">"S:path/to/file.txt"</code>.
 
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The lv_fs_if repository contains prepared drivers using POSIX, standard C and the FATFS API. See its README for the details.
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The lv_fs_if repository contains prepared drivers using POSIX, standard C and the FATFS API.  
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See its README for the details.
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|The lv_fs_if repository contains prepared drivers using POSIX, standard C and the FATFS API.
 +
 
 +
See its README for the details.
 
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To add a driver, a <code style="color: #bb0000;">lv_fs_drv_t</code> needs to be initialized like below. The <code style="color: #bb0000;">lv_fs_drv_t</code> needs to be static, global or dynamically allocated and not a local variable.
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To add a driver, a <code style="color: #bb0000;">lv_fs_drv_t</code> needs to be initialized like below.  
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 +
The <code style="color: #bb0000;">lv_fs_drv_t</code> needs to be static, global or dynamically allocated and not a local variable.
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<syntaxhighlight lang="C++" style="border:1px dashed gray;">
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static lv_fs_drv_t drv;                  /*Needs to be static or global*/
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lv_fs_drv_init(&drv);                    /*Basic initialization*/
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 +
drv.letter = 'S';                        /*An uppercase letter to identify the drive */
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drv.cache_size = my_cahce_size;          /*Cache size for reading in bytes. 0 to not cache.*/
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drv.ready_cb = my_ready_cb;              /*Callback to tell if the drive is ready to use */
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drv.open_cb = my_open_cb;                /*Callback to open a file */
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drv.close_cb = my_close_cb;              /*Callback to close a file */
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drv.read_cb = my_read_cb;                /*Callback to read a file */
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drv.write_cb = my_write_cb;              /*Callback to write a file */
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drv.seek_cb = my_seek_cb;                /*Callback to seek in a file (Move cursor) */
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drv.tell_cb = my_tell_cb;                /*Callback to tell the cursor position  */
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drv.dir_open_cb = my_dir_open_cb;        /*Callback to open directory to read its content */
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drv.dir_read_cb = my_dir_read_cb;        /*Callback to read a directory's content */
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drv.dir_close_cb = my_dir_close_cb;      /*Callback to close a directory */
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drv.user_data = my_user_data;            /*Any custom data if required*/
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lv_fs_drv_register(&drv);                /*Finally register the drive*/
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</syntaxhighlight>
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Any of the callbacks can be <code style="color: #bb0000;">NULL</code> to indicate that operation is not supported.
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|To add a driver, a <code style="color: #bb0000;">lv_fs_drv_t</code> needs to be initialized like below.
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The <code style="color: #bb0000;">lv_fs_drv_t</code> needs to be static, global or dynamically allocated and not a local variable.
 
<syntaxhighlight lang="C++" style="border:1px dashed gray;">
 
<syntaxhighlight lang="C++" style="border:1px dashed gray;">
 
  static lv_fs_drv_t drv;                  /*Needs to be static or global*/
 
  static lv_fs_drv_t drv;                  /*Needs to be static or global*/
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</syntaxhighlight>
 
</syntaxhighlight>
 
Any of the callbacks can be <code style="color: #bb0000;">NULL</code> to indicate that operation is not supported.
 
Any of the callbacks can be <code style="color: #bb0000;">NULL</code> to indicate that operation is not supported.
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The prototype of <code style="color: #bb0000;">open_cb</code> looks like this:
 
The prototype of <code style="color: #bb0000;">open_cb</code> looks like this:
 
  void * (*open_cb)(lv_fs_drv_t * drv, const char * path, lv_fs_mode_t mode);
 
  void * (*open_cb)(lv_fs_drv_t * drv, const char * path, lv_fs_mode_t mode);
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<code style="color: #bb0000;">path</code> is the path after the drive letter (e.g. "S:path/to/file.txt" -> "path/to/file.txt"). <code style="color: #bb0000;">mode</code> can be <code style="color: #bb0000;">LV_FS_MODE_WR</code> or <code style="color: #bb0000;">LV_FS_MODE_RD</code> to open for writes or reads.
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<code style="color: #bb0000;">path</code> is the path after the drive letter (e.g. "S:path/to/file.txt" -> "path/to/file.txt").  
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<code style="color: #bb0000;">mode</code> can be <code style="color: #bb0000;">LV_FS_MODE_WR</code> or <code style="color: #bb0000;">LV_FS_MODE_RD</code> to open for writes or reads.
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The return value is a pointer to a ''file object'' that describes the opened file or <code style="color: #bb0000;">NULL</code> if there were any issues (e.g. the file wasn't found).
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 +
The returned file object will be passed to other file system related callbacks. (see below)
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|The prototype of <code style="color: #bb0000;">open_cb</code> looks like this:
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void * (*open_cb)(lv_fs_drv_t * drv, const char * path, lv_fs_mode_t mode);
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<code style="color: #bb0000;">path</code> is the path after the drive letter (e.g. "S:path/to/file.txt" -> "path/to/file.txt").  
  
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The return value is a pointer to a ''file object'' that describes the opened file or <code style="color: #bb0000;">NULL</code> if there were any issues (e.g. the file wasn't found). The returned file object will be passed to other file system related callbacks. (see below)
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<code style="color: #bb0000;">mode</code> can be <code style="color: #bb0000;">LV_FS_MODE_WR</code> or <code style="color: #bb0000;">LV_FS_MODE_RD</code> to open for writes or reads.
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The return value is a pointer to a ''file object'' that describes the opened file or <code style="color: #bb0000;">NULL</code> if there were any issues (e.g. the file wasn't found).  
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 +
The returned file object will be passed to other file system related callbacks. (see below)
 
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The other callbacks are quite similar. For example <code style="color: #bb0000;">write_cb</code> looks like this:
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The other callbacks are quite similar.  
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For example <code style="color: #bb0000;">write_cb</code> looks like this:
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<syntaxhighlight lang="C++" style="border:1px dashed gray;">
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lv_fs_res_t (*write_cb)(lv_fs_drv_t * drv, void * file_p, const void * buf, uint32_t btw, uint32_t * bw);
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</syntaxhighlight>
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For <code style="color: #bb0000;">file_p</code>, LVGL passes the return value of <code style="color: #bb0000;">open_cb</code>, <code style="color: #bb0000;">buf</code> is the data to write, <code style="color: #bb0000;">btw</code> is the Bytes To Write, <code style="color: #bb0000;">bw</code> is the actually written bytes.
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For a template of these callbacks see lv_fs_template.c.
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|The other callbacks are quite similar.
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For example <code style="color: #bb0000;">write_cb</code> looks like this:
 
<syntaxhighlight lang="C++" style="border:1px dashed gray;">
 
<syntaxhighlight lang="C++" style="border:1px dashed gray;">
 
  lv_fs_res_t (*write_cb)(lv_fs_drv_t * drv, void * file_p, const void * buf, uint32_t btw, uint32_t * bw);
 
  lv_fs_res_t (*write_cb)(lv_fs_drv_t * drv, void * file_p, const void * buf, uint32_t btw, uint32_t * bw);
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For a template of these callbacks see lv_fs_template.c.
 
For a template of these callbacks see lv_fs_template.c.
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''The mode in <code style="color: #bb0000;">lv_fs_open</code> can be <code style="color: #bb0000;">LV_FS_MODE_WR</code> to open for writes only or <code style="color: #bb0000;">LV_FS_MODE_RD | LV_FS_MODE_WR</code> for both''
 
''The mode in <code style="color: #bb0000;">lv_fs_open</code> can be <code style="color: #bb0000;">LV_FS_MODE_WR</code> to open for writes only or <code style="color: #bb0000;">LV_FS_MODE_RD | LV_FS_MODE_WR</code> for both''
  
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This example shows how to read a directory's content. It's up to the driver how to mark directories in the result but it can be a good practice to insert a <code style="color: #bb0000;">'/'</code> in front of each directory name.
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This example shows how to read a directory's content.  
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It's up to the driver how to mark directories in the result but it can be a good practice to insert a <code style="color: #bb0000;">'/'</code> in front of each directory name.
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<syntaxhighlight lang="C++" style="border:1px dashed gray;">
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lv_fs_dir_t dir;
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lv_fs_res_t res;
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res = lv_fs_dir_open(&dir, "S:/folder");
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if(res != LV_FS_RES_OK) my_error_handling();
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char fn[256];
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while(1) {
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    res = lv_fs_dir_read(&dir, fn);
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    if(res != LV_FS_RES_OK) {
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        my_error_handling();
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        break;
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    }
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    /*fn is empty, if not more files to read*/
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    if(strlen(fn) == 0) {
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        break;
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    }
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    printf("%s\n", fn);
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}
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lv_fs_dir_close(&dir);
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</syntaxhighlight>
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|The example below shows how to read from a file:
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<syntaxhighlight lang="C++" style="border:1px dashed gray;">
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lv_fs_file_t f;
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lv_fs_res_t res;
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res = lv_fs_open(&f, "S:folder/file.txt", LV_FS_MODE_RD);
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if(res != LV_FS_RES_OK) my_error_handling();
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uint32_t read_num;
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uint8_t buf[8];
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res = lv_fs_read(&f, buf, 8, &read_num);
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if(res != LV_FS_RES_OK || read_num != 8) my_error_handling();
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lv_fs_close(&f);
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</syntaxhighlight>
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''The mode in <code style="color: #bb0000;">lv_fs_open</code> can be <code style="color: #bb0000;">LV_FS_MODE_WR</code> to open for writes only or <code style="color: #bb0000;">LV_FS_MODE_RD | LV_FS_MODE_WR</code> for both''
 +
 
 +
This example shows how to read a directory's content.
 +
 
 +
It's up to the driver how to mark directories in the result but it can be a good practice to insert a <code style="color: #bb0000;">'/'</code> in front of each directory name.
 
<syntaxhighlight lang="C++" style="border:1px dashed gray;">
 
<syntaxhighlight lang="C++" style="border:1px dashed gray;">
 
  lv_fs_dir_t dir;
 
  lv_fs_dir_t dir;
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  lv_fs_dir_close(&dir);
 
  lv_fs_dir_close(&dir);
 
</syntaxhighlight>
 
</syntaxhighlight>
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* seek
 
* seek
 
* tell
 
* tell
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|Image objects can be opened from files too (besides variables stored in the compiled program).
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To use files in image widgets the following callbacks are required:
 +
 
 +
* open
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* close
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* read
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* seek
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* tell
 
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Typedefs
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'''Typedefs'''
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">typedef uint8_t lv_fs_res_t </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">typedef uint8_t lv_fs_res_t </span>
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:
 
:
  
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Enums
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'''Enums'''
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">enum [anonymous] </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">enum [anonymous] </span>
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: Errors in the file system module.  ''Values:''
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: Errors in the file system module.   
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: '''''Values:'''''
 
: <span style="background-color: #eeeeee;">enumerator LV_FS_RES_OK </span>
 
: <span style="background-color: #eeeeee;">enumerator LV_FS_RES_OK </span>
 
::
 
::
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<span style="background-color:#e7f2fa;color:#2980b9;">enum [anonymous] </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">enum [anonymous] </span>
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: File open mode.  ''Values:''
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: File open mode.   
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: '''''Values:'''''
 
: <span style="background-color: #eeeeee;">enumerator LV_FS_MODE_WR </span>
 
: <span style="background-color: #eeeeee;">enumerator LV_FS_MODE_WR </span>
 
::
 
::
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<span style="background-color:#e7f2fa;color:#2980b9;">enum lv_fs_whence_t </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">enum lv_fs_whence_t </span>
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: Seek modes.  ''Va''''lues:''
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: Seek modes.   
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: '''''Values:'''''
 
: <span style="background-color: #eeeeee;">enumerator LV_FS_SEEK_SET </span>
 
: <span style="background-color: #eeeeee;">enumerator LV_FS_SEEK_SET </span>
 
:: Set the position from absolutely (from the start of file)
 
:: Set the position from absolutely (from the start of file)
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<span style="background-color:#e7f2fa;color:#2980b9;">void lv_fs_drv_init(lv_fs_drv_t *drv) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">void lv_fs_drv_init(lv_fs_drv_t *drv) </span>
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: Initialize a file system driver with default values. It is used to surly have known values in the fields ant not memory junk. After it you can set the fields.
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: Initialize a file system driver with default values.  
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: '''Parameters'''
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: It is used to surly have known values in the fields ant not memory junk.  
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:: drv -- pointer to driver variable to initialize
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: After it you can set the fields.
 +
:
 +
:'''Parameters'''
 +
:: '''drv''' -- pointer to driver variable to initialize
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">void lv_fs_drv_register(lv_fs_drv_t *drv) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">void lv_fs_drv_register(lv_fs_drv_t *drv) </span>
 
: Add a new drive
 
: Add a new drive
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: Parameters
+
: '''Parameters'''
−
:: drv -- pointer to an lv_fs_drv_t structure which is inited with the corresponding function pointers. Only pointer is saved, so the driver should be static or dynamically allocated.
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:: '''drv''' -- pointer to an lv_fs_drv_t structure which is inited with the corresponding function pointers.  
 +
:: Only pointer is saved, so the driver should be static or dynamically allocated.
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_drv_t *lv_fs_get_drv(char letter) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_drv_t *lv_fs_get_drv(char letter) </span>
 
: Give a pointer to a driver from its letter
 
: Give a pointer to a driver from its letter
−
: Parameters
+
: '''Parameters'''
−
:: letter -- the driver letter
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:: '''letter''' -- the driver letter
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: Returns
+
: '''Returns'''
 
:: pointer to a driver or NULL if not found
 
:: pointer to a driver or NULL if not found
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">bool lv_fs_is_ready(char letter) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">bool lv_fs_is_ready(char letter) </span>
 
: Test if a drive is ready or not. If the <code style="color: #bb0000;">ready</code> function was not initialized <code style="color: #bb0000;">true</code> will be returned.
 
: Test if a drive is ready or not. If the <code style="color: #bb0000;">ready</code> function was not initialized <code style="color: #bb0000;">true</code> will be returned.
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: Parameters
+
: '''Parameters'''
−
:: letter -- letter of the drive
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:: '''letter''' -- letter of the drive
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: Returns
+
: '''Returns'''
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:: true: drive is ready; false: drive is not ready
+
:: '''true''': drive is ready; false: drive is not ready
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_open(lv_fs_file_t *file_p, const char *path, lv_fs_mode_t mode) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_open(lv_fs_file_t *file_p, const char *path, lv_fs_mode_t mode) </span>
 
: Open a file
 
: Open a file
−
: Parameters
+
: '''Parameters'''
−
::* file_p -- pointer to a lv_fs_file_t variable
+
::* '''file_p''' -- pointer to a lv_fs_file_t variable
  
−
::* path -- path to the file beginning with the driver letter (e.g. S:/folder/file.txt)
+
::* '''path''' -- path to the file beginning with the driver letter (e.g. S:/folder/file.txt)
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::* mode -- read: FS_MODE_RD, write: FS_MODE_WR, both: FS_MODE_RD | FS_MODE_WR
+
::* '''mode''' -- read: FS_MODE_RD, write: FS_MODE_WR, both: FS_MODE_RD | FS_MODE_WR
−
: Returns
+
: '''Returns'''
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_close(lv_fs_file_t *file_p) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_close(lv_fs_file_t *file_p) </span>
 
: Close an already opened file
 
: Close an already opened file
−
: Parameters
+
: '''Parameters'''
−
:: file_p -- pointer to a lv_fs_file_t variable
+
:: '''file_p''' -- pointer to a lv_fs_file_t variable
−
: Returns
+
: '''Returns'''
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_read(lv_fs_file_t *file_p, void *buf, uint32_t btr, uint32_t *br) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_read(lv_fs_file_t *file_p, void *buf, uint32_t btr, uint32_t *br) </span>
 
: Read from a file
 
: Read from a file
−
: Parameters
+
: '''Parameters'''
−
::* file_p -- pointer to a lv_fs_file_t variable
+
::* '''file_p''' -- pointer to a lv_fs_file_t variable
−
::* buf -- pointer to a buffer where the read bytes are stored
+
::* '''buf''' -- pointer to a buffer where the read bytes are stored
−
::* btr -- Bytes To Read
+
::* '''btr''' -- Bytes To Read
−
::* br -- the number of real read bytes (Bytes Read). NULL if unused.
+
::* '''br''' -- the number of real read bytes (Bytes Read). NULL if unused.
−
: Returns
+
: '''Returns'''
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_write(lv_fs_file_t *file_p, const void *buf, uint32_t btw, uint32_t *bw) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_write(lv_fs_file_t *file_p, const void *buf, uint32_t btw, uint32_t *bw) </span>
 
: Write into a file
 
: Write into a file
−
: Parameters
+
: '''Parameters'''
−
::* file_p -- pointer to a lv_fs_file_t variable
+
::* '''file_p''' -- pointer to a lv_fs_file_t variable
−
::* buf -- pointer to a buffer with the bytes to write
+
::* '''buf''' -- pointer to a buffer with the bytes to write
−
::* btr -- Bytes To Write
+
::* '''btr''' -- Bytes To Write
−
::* br -- the number of real written bytes (Bytes Written). NULL if unused.
+
::* '''br''' -- the number of real written bytes (Bytes Written). NULL if unused.
−
: Returns
+
: '''Returns'''
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_seek(lv_fs_file_t *file_p, uint32_t pos, lv_fs_whence_t whence) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_seek(lv_fs_file_t *file_p, uint32_t pos, lv_fs_whence_t whence) </span>
 
: Set the position of the 'cursor' (read write pointer) in a file
 
: Set the position of the 'cursor' (read write pointer) in a file
−
: Parameters
+
: '''Parameters'''
−
::* file_p -- pointer to a lv_fs_file_t variable
+
::* '''file_p''' -- pointer to a lv_fs_file_t variable
−
::* pos -- the new position expressed in bytes index (0: start of file)
+
::* '''pos''' -- the new position expressed in bytes index (0: start of file)
−
::* whence -- tells from where set the position. See @lv_fs_whence_t
+
::* '''whence''' -- tells from where set the position. See @lv_fs_whence_t
−
: Returns
+
: '''Returns'''
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_tell(lv_fs_file_t *file_p, uint32_t *pos) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_tell(lv_fs_file_t *file_p, uint32_t *pos) </span>
 
: Give the position of the read write pointer
 
: Give the position of the read write pointer
−
: Parameters
+
: '''Parameters'''
−
::* file_p -- pointer to a lv_fs_file_t variable
+
::* '''file_p''' -- pointer to a lv_fs_file_t variable
−
::* pos_p -- pointer to store the position of the read write pointer
+
::* '''pos_p''' -- pointer to store the position of the read write pointer
−
: Returns
+
: '''Returns'''
 
:: LV_FS_RES_OK or any error from 'fs_res_t'
 
:: LV_FS_RES_OK or any error from 'fs_res_t'
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_dir_open(lv_fs_dir_t *rddir_p, const char *path) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_dir_open(lv_fs_dir_t *rddir_p, const char *path) </span>
 
: Initialize a 'fs_dir_t' variable for directory reading
 
: Initialize a 'fs_dir_t' variable for directory reading
−
: Parameters
+
: '''Parameters'''
−
::* rddir_p -- pointer to a 'lv_fs_dir_t' variable
+
::* '''rddir_p''' -- pointer to a 'lv_fs_dir_t' variable
−
::* path -- path to a directory
+
::* '''path''' -- path to a directory
−
: Returns
+
: '''Returns'''
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_dir_read(lv_fs_dir_t *rddir_p, char *fn) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_dir_read(lv_fs_dir_t *rddir_p, char *fn) </span>
 
: Read the next filename form a directory. The name of the directories will begin with '/'
 
: Read the next filename form a directory. The name of the directories will begin with '/'
−
: Parameters
+
: '''Parameters'''
−
::* rddir_p -- pointer to an initialized 'fs_dir_t' variable
+
::* '''rddir_p''' -- pointer to an initialized 'fs_dir_t' variable
−
::* fn -- pointer to a buffer to store the filename
+
::* '''fn''' -- pointer to a buffer to store the filename
−
: Returns
+
: '''Returns'''
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_dir_close(lv_fs_dir_t *rddir_p) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">lv_fs_res_t lv_fs_dir_close(lv_fs_dir_t *rddir_p) </span>
 
: Close the directory reading
 
: Close the directory reading
−
: Parameters
+
: '''Parameters'''
−
:: rddir_p -- pointer to an initialized 'fs_dir_t' variable
+
:: '''rddir_p''' -- pointer to an initialized 'fs_dir_t' variable
−
: Returns
+
: '''Returns'''
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
 
:: LV_FS_RES_OK or any error from lv_fs_res_t enum
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">char *lv_fs_get_letters(char *buf) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">char *lv_fs_get_letters(char *buf) </span>
 
: Fill a buffer with the letters of existing drivers
 
: Fill a buffer with the letters of existing drivers
−
: Parameters
+
: '''Parameters'''
−
:: buf -- buffer to store the letters ('\0' added after the last letter)
+
:: '''buf''' -- buffer to store the letters ('\0' added after the last letter)
−
: Returns
+
: '''Returns'''
 
:: the buffer
 
:: the buffer
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">const char *lv_fs_get_ext(const char *fn) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">const char *lv_fs_get_ext(const char *fn) </span>
 
: Return with the extension of the filename
 
: Return with the extension of the filename
−
: Parameters
+
: '''Parameters'''
−
:: fn -- string with a filename
+
:: '''fn''' -- string with a filename
−
: Returns
+
: '''Returns'''
 
:: pointer to the beginning extension or empty string if no extension
 
:: pointer to the beginning extension or empty string if no extension
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">char *lv_fs_up(char *path) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">char *lv_fs_up(char *path) </span>
 
: Step up one level
 
: Step up one level
−
: Parameters
+
: '''Parameters'''
−
:: path -- pointer to a file name
+
:: '''path''' -- pointer to a file name
−
: Returns
+
: '''Returns'''
 
:: the truncated file name
 
:: the truncated file name
  
 
<span style="background-color:#e7f2fa;color:#2980b9;">const char *lv_fs_get_last(const char *path) </span>
 
<span style="background-color:#e7f2fa;color:#2980b9;">const char *lv_fs_get_last(const char *path) </span>
 
: Get the last element of a path (e.g. U:/folder/file -> file)
 
: Get the last element of a path (e.g. U:/folder/file -> file)
−
: Parameters
+
: '''Parameters'''
−
:: path -- pointer to a file name
+
:: '''path''' -- pointer to a file name
−
: Returns
+
: '''Returns'''
 
:: pointer to the beginning of the last element in the path
 
:: pointer to the beginning of the last element in the path
  

2022年7月2日 (土) 10:36時点における版

https://docs.lvgl.io/8.2/overview/file-system.html

File system

英文 自動翻訳

LVGL has a 'File system' abstraction module that enables you to attach any type of file system.

A file system is identified by an assigned drive letter.

For example, if an SD card is associated with the letter 'S', a file can be reached using "S:path/to/file.txt".

LVGL has a 'File system' abstraction module that enables you to attach any type of file system.

A file system is identified by an assigned drive letter.

For example, if an SD card is associated with the letter 'S', a file can be reached using "S:path/to/file.txt".

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Ready to use drivers

英文 自動翻訳

The lv_fs_if repository contains prepared drivers using POSIX, standard C and the FATFS API.

See its README for the details.

The lv_fs_if repository contains prepared drivers using POSIX, standard C and the FATFS API.

See its README for the details.

戻る : Previous


Adding a driver

Registering a driver

英文 自動翻訳

To add a driver, a lv_fs_drv_t needs to be initialized like below.

The lv_fs_drv_t needs to be static, global or dynamically allocated and not a local variable. 

 static lv_fs_drv_t drv;                   /*Needs to be static or global*/
 lv_fs_drv_init(&drv);                     /*Basic initialization*/
 
 drv.letter = 'S';                         /*An uppercase letter to identify the drive */
 drv.cache_size = my_cahce_size;           /*Cache size for reading in bytes. 0 to not cache.*/
 
 drv.ready_cb = my_ready_cb;               /*Callback to tell if the drive is ready to use */
 drv.open_cb = my_open_cb;                 /*Callback to open a file */
 drv.close_cb = my_close_cb;               /*Callback to close a file */
 drv.read_cb = my_read_cb;                 /*Callback to read a file */
 drv.write_cb = my_write_cb;               /*Callback to write a file */
 drv.seek_cb = my_seek_cb;                 /*Callback to seek in a file (Move cursor) */
 drv.tell_cb = my_tell_cb;                 /*Callback to tell the cursor position  */
 
 drv.dir_open_cb = my_dir_open_cb;         /*Callback to open directory to read its content */
 drv.dir_read_cb = my_dir_read_cb;         /*Callback to read a directory's content */
 drv.dir_close_cb = my_dir_close_cb;       /*Callback to close a directory */
 
 drv.user_data = my_user_data;             /*Any custom data if required*/
 
 lv_fs_drv_register(&drv);                 /*Finally register the drive*/

Any of the callbacks can be NULL to indicate that operation is not supported.

To add a driver, a lv_fs_drv_t needs to be initialized like below.

The lv_fs_drv_t needs to be static, global or dynamically allocated and not a local variable. 

 static lv_fs_drv_t drv;                   /*Needs to be static or global*/
 lv_fs_drv_init(&drv);                     /*Basic initialization*/
 
 drv.letter = 'S';                         /*An uppercase letter to identify the drive */
 drv.cache_size = my_cahce_size;           /*Cache size for reading in bytes. 0 to not cache.*/
 
 drv.ready_cb = my_ready_cb;               /*Callback to tell if the drive is ready to use */
 drv.open_cb = my_open_cb;                 /*Callback to open a file */
 drv.close_cb = my_close_cb;               /*Callback to close a file */
 drv.read_cb = my_read_cb;                 /*Callback to read a file */
 drv.write_cb = my_write_cb;               /*Callback to write a file */
 drv.seek_cb = my_seek_cb;                 /*Callback to seek in a file (Move cursor) */
 drv.tell_cb = my_tell_cb;                 /*Callback to tell the cursor position  */
 
 drv.dir_open_cb = my_dir_open_cb;         /*Callback to open directory to read its content */
 drv.dir_read_cb = my_dir_read_cb;         /*Callback to read a directory's content */
 drv.dir_close_cb = my_dir_close_cb;       /*Callback to close a directory */
 
 drv.user_data = my_user_data;             /*Any custom data if required*/
 
 lv_fs_drv_register(&drv);                 /*Finally register the drive*/

Any of the callbacks can be NULL to indicate that operation is not supported.

戻る : Previous


Implementing the callbacks

Open callback

英文 自動翻訳

The prototype of open_cb looks like this: 

void * (*open_cb)(lv_fs_drv_t * drv, const char * path, lv_fs_mode_t mode);

path is the path after the drive letter (e.g. "S:path/to/file.txt" -> "path/to/file.txt").

mode can be LV_FS_MODE_WR or LV_FS_MODE_RD to open for writes or reads.

The return value is a pointer to a file object that describes the opened file or NULL if there were any issues (e.g. the file wasn't found).

The returned file object will be passed to other file system related callbacks. (see below)

The prototype of open_cb looks like this: 
void * (*open_cb)(lv_fs_drv_t * drv, const char * path, lv_fs_mode_t mode);

path is the path after the drive letter (e.g. "S:path/to/file.txt" -> "path/to/file.txt").

mode can be LV_FS_MODE_WR or LV_FS_MODE_RD to open for writes or reads.

The return value is a pointer to a file object that describes the opened file or NULL if there were any issues (e.g. the file wasn't found).

The returned file object will be passed to other file system related callbacks. (see below)

戻る : Previous


Other callbacks

英文 自動翻訳

The other callbacks are quite similar.

For example write_cb looks like this: 

 lv_fs_res_t (*write_cb)(lv_fs_drv_t * drv, void * file_p, const void * buf, uint32_t btw, uint32_t * bw);

For file_p, LVGL passes the return value of open_cb, buf is the data to write, btw is the Bytes To Write, bw is the actually written bytes.

For a template of these callbacks see lv_fs_template.c.

The other callbacks are quite similar.

For example write_cb looks like this: 

 lv_fs_res_t (*write_cb)(lv_fs_drv_t * drv, void * file_p, const void * buf, uint32_t btw, uint32_t * bw);

For file_p, LVGL passes the return value of open_cb, buf is the data to write, btw is the Bytes To Write, bw is the actually written bytes.

For a template of these callbacks see lv_fs_template.c.

戻る : Previous


Usage example

英文 自動翻訳

The example below shows how to read from a file: 

 lv_fs_file_t f;
 lv_fs_res_t res;
 res = lv_fs_open(&f, "S:folder/file.txt", LV_FS_MODE_RD);
 if(res != LV_FS_RES_OK) my_error_handling();
 
 uint32_t read_num;
 uint8_t buf[8];
 res = lv_fs_read(&f, buf, 8, &read_num);
 if(res != LV_FS_RES_OK || read_num != 8) my_error_handling();
 
 lv_fs_close(&f);

The mode in lv_fs_open can be LV_FS_MODE_WR to open for writes only or LV_FS_MODE_RD | LV_FS_MODE_WR for both

This example shows how to read a directory's content.

It's up to the driver how to mark directories in the result but it can be a good practice to insert a '/' in front of each directory name. 

 lv_fs_dir_t dir;
 lv_fs_res_t res;
 res = lv_fs_dir_open(&dir, "S:/folder");
 if(res != LV_FS_RES_OK) my_error_handling();
 
 char fn[256];
 while(1) {
     res = lv_fs_dir_read(&dir, fn);
     if(res != LV_FS_RES_OK) {
         my_error_handling();
         break;
     }
 
     /*fn is empty, if not more files to read*/
     if(strlen(fn) == 0) {
         break;
     }
 
     printf("%s\n", fn);
 }
 
 lv_fs_dir_close(&dir);
The example below shows how to read from a file: 
 lv_fs_file_t f;
 lv_fs_res_t res;
 res = lv_fs_open(&f, "S:folder/file.txt", LV_FS_MODE_RD);
 if(res != LV_FS_RES_OK) my_error_handling();
 
 uint32_t read_num;
 uint8_t buf[8];
 res = lv_fs_read(&f, buf, 8, &read_num);
 if(res != LV_FS_RES_OK || read_num != 8) my_error_handling();
 
 lv_fs_close(&f);

The mode in lv_fs_open can be LV_FS_MODE_WR to open for writes only or LV_FS_MODE_RD | LV_FS_MODE_WR for both

This example shows how to read a directory's content.

It's up to the driver how to mark directories in the result but it can be a good practice to insert a '/' in front of each directory name. 

 lv_fs_dir_t dir;
 lv_fs_res_t res;
 res = lv_fs_dir_open(&dir, "S:/folder");
 if(res != LV_FS_RES_OK) my_error_handling();
 
 char fn[256];
 while(1) {
     res = lv_fs_dir_read(&dir, fn);
     if(res != LV_FS_RES_OK) {
         my_error_handling();
         break;
     }
 
     /*fn is empty, if not more files to read*/
     if(strlen(fn) == 0) {
         break;
     }
 
     printf("%s\n", fn);
 }
 
 lv_fs_dir_close(&dir);
戻る : Previous


Use drives for images

英文 自動翻訳

Image objects can be opened from files too (besides variables stored in the compiled program).



To use files in image widgets the following callbacks are required:

  • open
  • close
  • read
  • seek
  • tell
 Image objects can be opened from files too (besides variables stored in the compiled program).



To use files in image widgets the following callbacks are required:

  • open
  • close
  • read
  • seek
  • tell
戻る : Previous


API

英文 自動翻訳

Typedefs

typedef uint8_t lv_fs_res_t

typedef uint8_t lv_fs_mode_t

typedef struct _lv_fs_drv_t lv_fs_drv_t

Enums

enum [anonymous]

Errors in the file system module.
Values:
enumerator LV_FS_RES_OK
enumerator LV_FS_RES_HW_ERR
enumerator LV_FS_RES_FS_ERR
enumerator LV_FS_RES_NOT_EX
enumerator LV_FS_RES_FULL
enumerator LV_FS_RES_LOCKED
enumerator LV_FS_RES_DENIED
enumerator LV_FS_RES_BUSY
enumerator LV_FS_RES_TOUT
enumerator LV_FS_RES_NOT_IMP
enumerator LV_FS_RES_OUT_OF_MEM
enumerator LV_FS_RES_INV_PARAM
enumerator LV_FS_RES_UNKNOWN

enum [anonymous]

File open mode.
Values:
enumerator LV_FS_MODE_WR
enumerator LV_FS_MODE_RD

enum lv_fs_whence_t

Seek modes.
Values:
enumerator LV_FS_SEEK_SET
Set the position from absolutely (from the start of file)
enumerator LV_FS_SEEK_CUR
Set the position from the current position
enumerator LV_FS_SEEK_END
Set the position from the end of the file

Functions

void _lv_fs_init(void)

Initialize the File system interface

void lv_fs_drv_init(lv_fs_drv_t *drv)

Initialize a file system driver with default values.
It is used to surly have known values in the fields ant not memory junk.
After it you can set the fields.
Parameters
drv -- pointer to driver variable to initialize

void lv_fs_drv_register(lv_fs_drv_t *drv)

Add a new drive
Parameters
drv -- pointer to an lv_fs_drv_t structure which is inited with the corresponding function pointers.
Only pointer is saved, so the driver should be static or dynamically allocated.

lv_fs_drv_t *lv_fs_get_drv(char letter)

Give a pointer to a driver from its letter
Parameters
letter -- the driver letter
Returns
pointer to a driver or NULL if not found

bool lv_fs_is_ready(char letter)

Test if a drive is ready or not. If the ready function was not initialized true will be returned.
Parameters
letter -- letter of the drive
Returns
true: drive is ready; false: drive is not ready

lv_fs_res_t lv_fs_open(lv_fs_file_t *file_p, const char *path, lv_fs_mode_t mode)

Open a file
Parameters
  • file_p -- pointer to a lv_fs_file_t variable
  • path -- path to the file beginning with the driver letter (e.g. S:/folder/file.txt)
  • mode -- read: FS_MODE_RD, write: FS_MODE_WR, both: FS_MODE_RD | FS_MODE_WR
Returns
LV_FS_RES_OK or any error from lv_fs_res_t enum

lv_fs_res_t lv_fs_close(lv_fs_file_t *file_p)

Close an already opened file
Parameters
file_p -- pointer to a lv_fs_file_t variable
Returns
LV_FS_RES_OK or any error from lv_fs_res_t enum

lv_fs_res_t lv_fs_read(lv_fs_file_t *file_p, void *buf, uint32_t btr, uint32_t *br)

Read from a file
Parameters
  • file_p -- pointer to a lv_fs_file_t variable
  • buf -- pointer to a buffer where the read bytes are stored
  • btr -- Bytes To Read
  • br -- the number of real read bytes (Bytes Read). NULL if unused.
Returns
LV_FS_RES_OK or any error from lv_fs_res_t enum

lv_fs_res_t lv_fs_write(lv_fs_file_t *file_p, const void *buf, uint32_t btw, uint32_t *bw)

Write into a file
Parameters
  • file_p -- pointer to a lv_fs_file_t variable
  • buf -- pointer to a buffer with the bytes to write
  • btr -- Bytes To Write
  • br -- the number of real written bytes (Bytes Written). NULL if unused.
Returns
LV_FS_RES_OK or any error from lv_fs_res_t enum

lv_fs_res_t lv_fs_seek(lv_fs_file_t *file_p, uint32_t pos, lv_fs_whence_t whence)

Set the position of the 'cursor' (read write pointer) in a file
Parameters
  • file_p -- pointer to a lv_fs_file_t variable
  • pos -- the new position expressed in bytes index (0: start of file)
  • whence -- tells from where set the position. See @lv_fs_whence_t
Returns
LV_FS_RES_OK or any error from lv_fs_res_t enum

lv_fs_res_t lv_fs_tell(lv_fs_file_t *file_p, uint32_t *pos)

Give the position of the read write pointer
Parameters
  • file_p -- pointer to a lv_fs_file_t variable
  • pos_p -- pointer to store the position of the read write pointer
Returns
LV_FS_RES_OK or any error from 'fs_res_t'

lv_fs_res_t lv_fs_dir_open(lv_fs_dir_t *rddir_p, const char *path)

Initialize a 'fs_dir_t' variable for directory reading
Parameters
  • rddir_p -- pointer to a 'lv_fs_dir_t' variable
  • path -- path to a directory
Returns
LV_FS_RES_OK or any error from lv_fs_res_t enum

lv_fs_res_t lv_fs_dir_read(lv_fs_dir_t *rddir_p, char *fn)

Read the next filename form a directory. The name of the directories will begin with '/'
Parameters
  • rddir_p -- pointer to an initialized 'fs_dir_t' variable
  • fn -- pointer to a buffer to store the filename
Returns
LV_FS_RES_OK or any error from lv_fs_res_t enum

lv_fs_res_t lv_fs_dir_close(lv_fs_dir_t *rddir_p)

Close the directory reading
Parameters
rddir_p -- pointer to an initialized 'fs_dir_t' variable
Returns
LV_FS_RES_OK or any error from lv_fs_res_t enum

char *lv_fs_get_letters(char *buf)

Fill a buffer with the letters of existing drivers
Parameters
buf -- buffer to store the letters ('\0' added after the last letter)
Returns
the buffer

const char *lv_fs_get_ext(const char *fn)

Return with the extension of the filename
Parameters
fn -- string with a filename
Returns
pointer to the beginning extension or empty string if no extension

char *lv_fs_up(char *path)

Step up one level
Parameters
path -- pointer to a file name
Returns
the truncated file name

const char *lv_fs_get_last(const char *path)

Get the last element of a path (e.g. U:/folder/file -> file)
Parameters
path -- pointer to a file name
Returns
pointer to the beginning of the last element in the path

struct _lv_fs_drv_t

Public Members
char letter
uint16_t cache_size
bool (*ready_cb)(struct _lv_fs_drv_t *drv)
void *(*open_cb)(struct _lv_fs_drv_t *drv, const char *path, lv_fs_mode_t mode)
lv_fs_res_t (*close_cb)(struct _lv_fs_drv_t *drv, void *file_p)
lv_fs_res_t (*read_cb)(struct _lv_fs_drv_t *drv, void *file_p, void *buf, uint32_t btr, uint32_t *br)
lv_fs_res_t (*write_cb)(struct _lv_fs_drv_t *drv, void *file_p, const void *buf, uint32_t btw, uint32_t *bw)
lv_fs_res_t (*seek_cb)(struct _lv_fs_drv_t *drv, void *file_p, uint32_t pos, lv_fs_whence_t whence)
lv_fs_res_t (*tell_cb)(struct _lv_fs_drv_t *drv, void *file_p, uint32_t *pos_p)
void *(*dir_open_cb)(struct _lv_fs_drv_t *drv, const char *path)
lv_fs_res_t (*dir_read_cb)(struct _lv_fs_drv_t *drv, void *rddir_p, char *fn)
lv_fs_res_t (*dir_close_cb)(struct _lv_fs_drv_t *drv, void *rddir_p)
void *user_data
Custom file user data

struct lv_fs_file_cache_t

Public Members
uint32_t start
uint32_t end
uint32_t file_position
void *buffer

struct lv_fs_file_t

Public Members
void *file_d
lv_fs_drv_t *drv
lv_fs_file_cache_t *cache

struct lv_fs_dir_t

Public Members
void *dir_d
lv_fs_drv_t *drv


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