stmhal: Add fatfs support, working with flash and SD card.

stmhal/Makefile

@@ -10,7 +10,7 @@ CMSIS_DIR=cmsis
 HAL_DIR=hal
 USBDEV_DIR=usbdev
 #USBHOST_DIR=usbhost
-#FATFS_DIR=fatfs
+FATFS_DIR=fatfs
 #CC3K_DIR=cc3k
 DFU=../tools/dfu.py
 
@@ -23,7 +23,7 @@ INC += -I$(CMSIS_DIR)/devinc
 INC += -I$(HAL_DIR)/inc
 INC += -I$(USBDEV_DIR)/core/inc -I$(USBDEV_DIR)/class/cdc/inc
 #INC += -I$(USBHOST_DIR)
-#INC += -I$(FATFS_DIR)
+INC += -I$(FATFS_DIR)/src
 #INC += -I$(CC3K_DIR)
 
 CFLAGS_CORTEX_M4 = -mthumb -mtune=cortex-m4 -mabi=aapcs-linux -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard -fsingle-precision-constant -Wdouble-promotion
@@ -80,7 +80,9 @@ SRC_C = \
 	rtc.c \
 	flash.c \
 	storage.c \
+	file.c \
 	sdcard.c \
+	diskio.c \
 
 #	lcd.c \
 #	servo.c \
@@ -89,7 +91,6 @@ SRC_C = \
 #	audio.c \
 #	i2c.c \
 #	adc.c \
-#	file.c \
 #	pybwlan.c \
 
 SRC_S = \
@@ -137,10 +138,9 @@ SRC_USBDEV = $(addprefix $(USBDEV_DIR)/,\
 	usbd_storage_msd.c \
 	)
 
-SRC_FATFS = $(addprefix $(FATFS_DIR)/,\
+SRC_FATFS = $(addprefix $(FATFS_DIR)/src/,\
 	ff.c \
-	diskio.c \
-	ccsbcs.c \
+	option/ccsbcs.c \
 	)
 
 SRC_CC3K = $(addprefix $(CC3K_DIR)/,\
@@ -162,9 +162,7 @@ OBJ += $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_S:.s=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_HAL:.c=.o))
 OBJ += $(addprefix $(BUILD)/, $(SRC_USBDEV:.c=.o))
-#OBJ += $(addprefix $(BUILD)/, $(SRC_STMUSBD:.c=.o))
-#OBJ += $(addprefix $(BUILD)/, $(SRC_STMUSBH:.c=.o))
-#OBJ += $(addprefix $(BUILD)/, $(SRC_FATFS:.c=.o))
+OBJ += $(addprefix $(BUILD)/, $(SRC_FATFS:.c=.o))
 #OBJ += $(addprefix $(BUILD)/, $(SRC_CC3K:.c=.o))
 OBJ += $(BUILD)/pins_$(BOARD).o
 

stmhal/diskio.c

+/*-----------------------------------------------------------------------*/
+/* Low level disk I/O module skeleton for FatFs     (C)ChaN, 2013        */
+/*-----------------------------------------------------------------------*/
+/* If a working storage control module is available, it should be        */
+/* attached to the FatFs via a glue function rather than modifying it.   */
+/* This is an example of glue functions to attach various exsisting      */
+/* storage control module to the FatFs module with a defined API.        */
+/*-----------------------------------------------------------------------*/
+
+#include <stdint.h>
+#include <stdio.h>
+#include "ff.h"        /* FatFs lower layer API */
+#include "diskio.h"        /* FatFs lower layer API */
+#include "misc.h"
+#include "storage.h"
+#include "sdcard.h"
+
+PARTITION VolToPart[] = {
+    {0, 1},     // Logical drive 0 ==> Physical drive 0, 1st partition
+    {1, 0},     // Logical drive 1 ==> Physical drive 1 (auto detection)
+    /*
+    {0, 2},     // Logical drive 2 ==> Physical drive 0, 2nd partition
+    {0, 3},     // Logical drive 3 ==> Physical drive 0, 3rd partition
+    */
+};
+
+/* Definitions of physical drive number for each media */
+#define PD_FLASH (0)
+#define PD_SDCARD (1)
+
+/*-----------------------------------------------------------------------*/
+/* Initialize a Drive                                                    */
+/*-----------------------------------------------------------------------*/
+
+DSTATUS disk_initialize (
+    BYTE pdrv                /* Physical drive nmuber (0..) */
+)
+{
+    switch (pdrv) {
+        case PD_FLASH:
+            storage_init();
+            return 0;
+
+        case PD_SDCARD:
+            if (!sdcard_power_on()) {
+                return STA_NODISK;
+            }
+            // TODO return STA_PROTECT if SD card is read only
+            return 0;
+    }
+
+    return STA_NOINIT;
+}
+
+/*-----------------------------------------------------------------------*/
+/* Get Disk Status                                                       */
+/*-----------------------------------------------------------------------*/
+
+DSTATUS disk_status (
+    BYTE pdrv        /* Physical drive nmuber (0..) */
+)
+{
+    switch (pdrv) {
+        case PD_FLASH :
+            // flash is ready
+            return 0;
+
+        case PD_SDCARD:
+            // TODO return STA_PROTECT if SD card is read only
+            return 0;
+    }
+
+    return STA_NOINIT;
+}
+
+/*-----------------------------------------------------------------------*/
+/* Read Sector(s)                                                        */
+/*-----------------------------------------------------------------------*/
+
+DRESULT disk_read (
+    BYTE pdrv,        /* Physical drive nmuber (0..) */
+    BYTE *buff,        /* Data buffer to store read data */
+    DWORD sector,    /* Sector address (LBA) */
+    UINT count        /* Number of sectors to read (1..128) */
+)
+{
+    switch (pdrv) {
+        case PD_FLASH:
+            for (int i = 0; i < count; i++) {
+                if (!storage_read_block(buff + i * FLASH_BLOCK_SIZE, sector + i)) {
+                    return RES_ERROR;
+                }
+            }
+            return RES_OK;
+
+        case PD_SDCARD:
+            if (!sdcard_read_blocks(buff, sector, count)) {
+                return RES_ERROR;
+            }
+            return RES_OK;
+    }
+
+    return RES_PARERR;
+}
+
+/*-----------------------------------------------------------------------*/
+/* Write Sector(s)                                                       */
+/*-----------------------------------------------------------------------*/
+
+#if _USE_WRITE
+DRESULT disk_write (
+    BYTE pdrv,            /* Physical drive nmuber (0..) */
+    const BYTE *buff,    /* Data to be written */
+    DWORD sector,        /* Sector address (LBA) */
+    UINT count            /* Number of sectors to write (1..128) */
+)
+{
+    switch (pdrv) {
+        case PD_FLASH:
+            for (int i = 0; i < count; i++) {
+                if (!storage_write_block(buff + i * FLASH_BLOCK_SIZE, sector + i)) {
+                    return RES_ERROR;
+                }
+            }
+            return RES_OK;
+
+        case PD_SDCARD:
+            if (!sdcard_write_blocks(buff, sector, count)) {
+                return RES_ERROR;
+            }
+            return RES_OK;
+    }
+
+    return RES_PARERR;
+}
+#endif
+
+
+/*-----------------------------------------------------------------------*/
+/* Miscellaneous Functions                                               */
+/*-----------------------------------------------------------------------*/
+
+#if _USE_IOCTL
+DRESULT disk_ioctl (
+    BYTE pdrv,        /* Physical drive nmuber (0..) */
+    BYTE cmd,        /* Control code */
+    void *buff        /* Buffer to send/receive control data */
+)
+{
+    switch (pdrv) {
+        case PD_FLASH:
+            switch (cmd) {
+                case CTRL_SYNC:
+                    storage_flush();
+                    return RES_OK;
+
+                case GET_BLOCK_SIZE:
+                    *((DWORD*)buff) = 1; // high-level sector erase size in units of the small (512) block size
+                    return RES_OK;
+            }
+            break;
+
+        case PD_SDCARD:
+            switch (cmd) {
+                case CTRL_SYNC:
+                    return RES_OK;
+
+                case GET_BLOCK_SIZE:
+                    *((DWORD*)buff) = 1; // high-level sector erase size in units of the small (512) block size
+                    return RES_OK;
+            }
+            break;
+    }
+
+    return RES_PARERR;
+}
+#endif
+
+DWORD get_fattime (
+    void
+)
+{
+    // TODO replace with call to RTC
+    int year = 2013;
+    int month = 10;
+    int day = 12;
+    int hour = 21;
+    int minute = 42;
+    int second = 13;
+    return ((year - 1980) << 25) | ((month) << 21) | ((day) << 16) | ((hour) << 11) | ((minute) << 5) | (second / 2);
+}

stmhal/diskio.h

+/*-----------------------------------------------------------------------
+/  Low level disk interface modlue include file   (C)ChaN, 2013
+/-----------------------------------------------------------------------*/
+
+#ifndef _DISKIO_DEFINED
+#define _DISKIO_DEFINED
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define _USE_WRITE	1	/* 1: Enable disk_write function */
+#define _USE_IOCTL	1	/* 1: Enable disk_ioctl fucntion */
+
+#include "integer.h"
+
+
+/* Status of Disk Functions */
+typedef BYTE	DSTATUS;
+
+/* Results of Disk Functions */
+typedef enum {
+	RES_OK = 0,		/* 0: Successful */
+	RES_ERROR,		/* 1: R/W Error */
+	RES_WRPRT,		/* 2: Write Protected */
+	RES_NOTRDY,		/* 3: Not Ready */
+	RES_PARERR		/* 4: Invalid Parameter */
+} DRESULT;
+
+
+/*---------------------------------------*/
+/* Prototypes for disk control functions */
+
+
+DSTATUS disk_initialize (BYTE pdrv);
+DSTATUS disk_status (BYTE pdrv);
+DRESULT disk_read (BYTE pdrv, BYTE*buff, DWORD sector, UINT count);
+DRESULT disk_write (BYTE pdrv, const BYTE* buff, DWORD sector, UINT count);
+DRESULT disk_ioctl (BYTE pdrv, BYTE cmd, void* buff);
+
+DWORD get_fattime (void);
+
+/* Disk Status Bits (DSTATUS) */
+#define STA_NOINIT		0x01	/* Drive not initialized */
+#define STA_NODISK		0x02	/* No medium in the drive */
+#define STA_PROTECT		0x04	/* Write protected */
+
+
+/* Command code for disk_ioctrl fucntion */
+
+/* Generic command (used by FatFs) */
+#define CTRL_SYNC			0	/* Flush disk cache (for write functions) */
+#define GET_SECTOR_COUNT	1	/* Get media size (for only f_mkfs()) */
+#define GET_SECTOR_SIZE		2	/* Get sector size (for multiple sector size (_MAX_SS >= 1024)) */
+#define GET_BLOCK_SIZE		3	/* Get erase block size (for only f_mkfs()) */
+#define CTRL_ERASE_SECTOR	4	/* Force erased a block of sectors (for only _USE_ERASE) */
+
+/* Generic command (not used by FatFs) */
+#define CTRL_POWER			5	/* Get/Set power status */
+#define CTRL_LOCK			6	/* Lock/Unlock media removal */
+#define CTRL_EJECT			7	/* Eject media */
+#define CTRL_FORMAT			8	/* Create physical format on the media */
+
+/* MMC/SDC specific ioctl command */
+#define MMC_GET_TYPE		10	/* Get card type */
+#define MMC_GET_CSD			11	/* Get CSD */
+#define MMC_GET_CID			12	/* Get CID */
+#define MMC_GET_OCR			13	/* Get OCR */
+#define MMC_GET_SDSTAT		14	/* Get SD status */
+
+/* ATA/CF specific ioctl command */
+#define ATA_GET_REV			20	/* Get F/W revision */
+#define ATA_GET_MODEL		21	/* Get model name */
+#define ATA_GET_SN			22	/* Get serial number */
+
+
+/* MMC card type flags (MMC_GET_TYPE) */
+#define CT_MMC		0x01		/* MMC ver 3 */
+#define CT_SD1		0x02		/* SD ver 1 */
+#define CT_SD2		0x04		/* SD ver 2 */
+#define CT_SDC		(CT_SD1|CT_SD2)	/* SD */
+#define CT_BLOCK	0x08		/* Block addressing */
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

stmhal/ffconf.h

+/*---------------------------------------------------------------------------/
+/  FatFs - FAT file system module configuration file  R0.10  (C)ChaN, 2013
+/----------------------------------------------------------------------------/
+/
+/ CAUTION! Do not forget to make clean the project after any changes to
+/ the configuration options.
+/
+/----------------------------------------------------------------------------*/
+#ifndef _FFCONF
+#define _FFCONF 80960	/* Revision ID */
+
+#include "mpconfigport.h"
+
+/*---------------------------------------------------------------------------/
+/ Functions and Buffer Configurations
+/----------------------------------------------------------------------------*/
+
+#define	_FS_TINY		1	/* 0:Normal or 1:Tiny */
+/* When _FS_TINY is set to 1, FatFs uses the sector buffer in the file system
+/  object instead of the sector buffer in the individual file object for file
+/  data transfer. This reduces memory consumption 512 bytes each file object. */
+
+
+#define _FS_READONLY	0	/* 0:Read/Write or 1:Read only */
+/* Setting _FS_READONLY to 1 defines read only configuration. This removes
+/  writing functions, f_write(), f_sync(), f_unlink(), f_mkdir(), f_chmod(),
+/  f_rename(), f_truncate() and useless f_getfree(). */
+
+
+#define _FS_MINIMIZE	0	/* 0 to 3 */
+/* The _FS_MINIMIZE option defines minimization level to remove API functions.
+/
+/   0: All basic functions are enabled.
+/   1: f_stat(), f_getfree(), f_unlink(), f_mkdir(), f_chmod(), f_utime(),
+/      f_truncate() and f_rename() function are removed.
+/   2: f_opendir(), f_readdir() and f_closedir() are removed in addition to 1.
+/   3: f_lseek() function is removed in addition to 2. */
+
+
+#define	_USE_STRFUNC	0	/* 0:Disable or 1-2:Enable */
+/* To enable string functions, set _USE_STRFUNC to 1 or 2. */
+
+
+#define	_USE_MKFS		1	/* 0:Disable or 1:Enable */
+/* To enable f_mkfs() function, set _USE_MKFS to 1 and set _FS_READONLY to 0 */
+
+
+#define	_USE_FASTSEEK	0	/* 0:Disable or 1:Enable */
+/* To enable fast seek feature, set _USE_FASTSEEK to 1. */
+
+
+#define _USE_LABEL		0	/* 0:Disable or 1:Enable */
+/* To enable volume label functions, set _USE_LAVEL to 1 */
+
+
+#define	_USE_FORWARD	0	/* 0:Disable or 1:Enable */
+/* To enable f_forward() function, set _USE_FORWARD to 1 and set _FS_TINY to 1. */
+
+
+/*---------------------------------------------------------------------------/
+/ Locale and Namespace Configurations
+/----------------------------------------------------------------------------*/
+
+#define _CODE_PAGE	(MICROPY_LFN_CODE_PAGE)
+/* The _CODE_PAGE specifies the OEM code page to be used on the target system.
+/  Incorrect setting of the code page can cause a file open failure.
+/
+/   932  - Japanese Shift-JIS (DBCS, OEM, Windows)
+/   936  - Simplified Chinese GBK (DBCS, OEM, Windows)
+/   949  - Korean (DBCS, OEM, Windows)
+/   950  - Traditional Chinese Big5 (DBCS, OEM, Windows)
+/   1250 - Central Europe (Windows)
+/   1251 - Cyrillic (Windows)
+/   1252 - Latin 1 (Windows)
+/   1253 - Greek (Windows)
+/   1254 - Turkish (Windows)
+/   1255 - Hebrew (Windows)
+/   1256 - Arabic (Windows)
+/   1257 - Baltic (Windows)
+/   1258 - Vietnam (OEM, Windows)
+/   437  - U.S. (OEM)
+/   720  - Arabic (OEM)
+/   737  - Greek (OEM)
+/   775  - Baltic (OEM)
+/   850  - Multilingual Latin 1 (OEM)
+/   858  - Multilingual Latin 1 + Euro (OEM)
+/   852  - Latin 2 (OEM)
+/   855  - Cyrillic (OEM)
+/   866  - Russian (OEM)
+/   857  - Turkish (OEM)
+/   862  - Hebrew (OEM)
+/   874  - Thai (OEM, Windows)
+/   1    - ASCII (Valid for only non-LFN cfg.)
+*/
+
+#define	_USE_LFN	(MICROPY_ENABLE_LFN)		/* 0 to 3 */
+#define	_MAX_LFN	255		/* Maximum LFN length to handle (12 to 255) */
+/* The _USE_LFN option switches the LFN feature.
+/
+/   0: Disable LFN feature. _MAX_LFN has no effect.
+/   1: Enable LFN with static working buffer on the BSS. Always NOT reentrant.
+/   2: Enable LFN with dynamic working buffer on the STACK.
+/   3: Enable LFN with dynamic working buffer on the HEAP.
+/
+/  To enable LFN feature, Unicode handling functions ff_convert() and ff_wtoupper()
+/  function must be added to the project.
+/  The LFN working buffer occupies (_MAX_LFN + 1) * 2 bytes. When use stack for the
+/  working buffer, take care on stack overflow. When use heap memory for the working
+/  buffer, memory management functions, ff_memalloc() and ff_memfree(), must be added
+/  to the project. */
+
+
+#define	_LFN_UNICODE	0	/* 0:ANSI/OEM or 1:Unicode */
+/* To switch the character encoding on the FatFs API to Unicode, enable LFN feature
+/  and set _LFN_UNICODE to 1. */
+
+
+#define _STRF_ENCODE	3	/* 0:ANSI/OEM, 1:UTF-16LE, 2:UTF-16BE, 3:UTF-8 */
+/* When Unicode API is enabled, character encoding on the all FatFs API is switched
+/  to Unicode. This option selects the character encoding on the file to be read/written
+/  via string functions, f_gets(), f_putc(), f_puts and f_printf().
+/  This option has no effect when _LFN_UNICODE is 0. */
+
+
+#define _FS_RPATH		0	/* 0 to 2 */
+/* The _FS_RPATH option configures relative path feature.
+/
+/   0: Disable relative path feature and remove related functions.
+/   1: Enable relative path. f_chdrive() and f_chdir() function are available.
+/   2: f_getcwd() function is available in addition to 1.
+/
+/  Note that output of the f_readdir() fnction is affected by this option. */
+
+
+/*---------------------------------------------------------------------------/
+/ Drive/Volume Configurations
+/----------------------------------------------------------------------------*/
+
+#define _VOLUMES	2
+/* Number of volumes (logical drives) to be used. */
+
+
+#define	_MULTI_PARTITION	1	/* 0:Single partition, 1:Enable multiple partition */
+/* When set to 0, each volume is bound to the same physical drive number and
+/ it can mount only first primaly partition. When it is set to 1, each volume
+/ is tied to the partitions listed in VolToPart[]. */
+
+
+#define	_MAX_SS		512		/* 512, 1024, 2048 or 4096 */
+/* Maximum sector size to be handled.
+/  Always set 512 for memory card and hard disk but a larger value may be
+/  required for on-board flash memory, floppy disk and optical disk.
+/  When _MAX_SS is larger than 512, it configures FatFs to variable sector size
+/  and GET_SECTOR_SIZE command must be implemented to the disk_ioctl() function. */
+
+
+#define	_USE_ERASE	0	/* 0:Disable or 1:Enable */
+/* To enable sector erase feature, set _USE_ERASE to 1. Also CTRL_ERASE_SECTOR command
+/  should be added to the disk_ioctl() function. */
+
+
+#define _FS_NOFSINFO	0	/* 0 or 1 */
+/* If you need to know the correct free space on the FAT32 volume, set this
+/  option to 1 and f_getfree() function at first time after volume mount will
+/  force a full FAT scan.
+/
+/  0: Load all informations in the FSINFO if available.
+/  1: Do not trust free cluster count in the FSINFO.
+*/
+
+
+
+/*---------------------------------------------------------------------------/
+/ System Configurations
+/----------------------------------------------------------------------------*/
+
+#define _WORD_ACCESS	0	/* 0 or 1 */
+/* The _WORD_ACCESS option is an only platform dependent option. It defines
+/  which access method is used to the word data on the FAT volume.
+/
+/   0: Byte-by-byte access. Always compatible with all platforms.
+/   1: Word access. Do not choose this unless under both the following conditions.
+/
+/  * Byte order on the memory is little-endian.
+/  * Address miss-aligned word access is always allowed for all instructions.
+/
+/  If it is the case, _WORD_ACCESS can also be set to 1 to improve performance
+/  and reduce code size.
+*/
+
+
+/* A header file that defines sync object types on the O/S, such as
+/  windows.h, ucos_ii.h and semphr.h, must be included prior to ff.h. */
+
+#define _FS_REENTRANT	0		/* 0:Disable or 1:Enable */
+#define _FS_TIMEOUT		1000	/* Timeout period in unit of time ticks */
+#define	_SYNC_t			HANDLE	/* O/S dependent type of sync object. e.g. HANDLE, OS_EVENT*, ID and etc.. */
+
+/* The _FS_REENTRANT option switches the re-entrancy (thread safe) of the FatFs module.
+/
+/   0: Disable re-entrancy. _SYNC_t and _FS_TIMEOUT have no effect.
+/   1: Enable re-entrancy. Also user provided synchronization handlers,
+/      ff_req_grant(), ff_rel_grant(), ff_del_syncobj() and ff_cre_syncobj()
+/      function must be added to the project. */
+
+
+#define	_FS_LOCK	0	/* 0:Disable or >=1:Enable */
+/* To enable file lock control feature, set _FS_LOCK to 1 or greater.
+   The value defines how many files can be opened simultaneously. */
+
+
+#endif /* _FFCONFIG */

stmhal/file.c

+#include <stdio.h>
+
+#include "misc.h"
+#include "mpconfig.h"
+#include "qstr.h"
+#include "obj.h"
+#include "file.h"
+#include "ff.h"
+
+typedef struct _pyb_file_obj_t {
+    mp_obj_base_t base;
+    FIL fp;
+} pyb_file_obj_t;
+
+void file_obj_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
+    printf("<file %p>", self_in);
+}
+
+mp_obj_t file_obj_read(mp_obj_t self_in, mp_obj_t arg) {
+    pyb_file_obj_t *self = self_in;
+    int n = mp_obj_get_int(arg);
+    byte *buf = m_new(byte, n);
+    UINT n_out;
+    f_read(&self->fp, buf, n, &n_out);
+    return mp_obj_new_str(buf, n_out, false);
+}
+
+mp_obj_t file_obj_write(mp_obj_t self_in, mp_obj_t arg) {
+    pyb_file_obj_t *self = self_in;
+    uint l;
+    const char *s = mp_obj_str_get_data(arg, &l);
+    UINT n_out;
+    FRESULT res = f_write(&self->fp, s, l, &n_out);
+    if (res != FR_OK) {
+        printf("File error: could not write to file; error code %d\n", res);
+    } else if (n_out != l) {
+        printf("File error: could not write all data to file; wrote %d / %d bytes\n", n_out, l);
+    }
+    return mp_const_none;
+}
+
+mp_obj_t file_obj_close(mp_obj_t self_in) {
+    pyb_file_obj_t *self = self_in;
+    f_close(&self->fp);
+    return mp_const_none;
+}
+
+static MP_DEFINE_CONST_FUN_OBJ_2(file_obj_read_obj, file_obj_read);
+static MP_DEFINE_CONST_FUN_OBJ_2(file_obj_write_obj, file_obj_write);
+static MP_DEFINE_CONST_FUN_OBJ_1(file_obj_close_obj, file_obj_close);
+
+// TODO gc hook to close the file if not already closed
+
+static const mp_method_t file_methods[] = {
+    { "read", &file_obj_read_obj },
+    { "write", &file_obj_write_obj },
+    { "close", &file_obj_close_obj },
+    {NULL, NULL},
+};
+
+static const mp_obj_type_t file_obj_type = {
+    { &mp_type_type },
+    .name = MP_QSTR_File,
+    .print = file_obj_print,
+    .methods = file_methods,
+};
+
+STATIC mp_obj_t pyb_io_open(mp_obj_t o_filename, mp_obj_t o_mode) {
+    const char *filename = mp_obj_str_get_str(o_filename);
+    const char *mode = mp_obj_str_get_str(o_mode);
+    pyb_file_obj_t *self = m_new_obj(pyb_file_obj_t);
+    self->base.type = &file_obj_type;
+    if (mode[0] == 'r') {
+        // open for reading
+        FRESULT res = f_open(&self->fp, filename, FA_READ);
+        if (res != FR_OK) {
+            printf("FileNotFoundError: [Errno 2] No such file or directory: '%s'\n", filename);
+            return mp_const_none;
+        }
+    } else if (mode[0] == 'w') {
+        // open for writing, truncate the file first
+        FRESULT res = f_open(&self->fp, filename, FA_WRITE | FA_CREATE_ALWAYS);
+        if (res != FR_OK) {
+            printf("?FileError: could not create file: '%s'\n", filename);
+            return mp_const_none;
+        }
+    } else {
+        printf("ValueError: invalid mode: '%s'\n", mode);
+        return mp_const_none;