Skip to main content

STM32 USB MSD with SD Card

Build a low level driver for SD card, then the glue logic for FatFs and USB MSD is pretty much the same as Flash memory case posed before. In case of SD card, sector size is 512 in most of the cases. Thus the memory requirement is much relaxed. You can even allocate a file buffer that is bigger than the sector size.

FatFs site has a dedicated page for MMC/SDC, on which you can find fairly detailed explanation about how to interface MMC/SDC via SPI bus. Implementation should be straightforward until you encounter with cheap SD cards that do not behave very well.

In such cases, you either have to protect your code with redundancy or just stick with quality devices. If you choose SanDisk or Kingston brand, you will be safe. ADATA on the other hand, frequently generates timeout error at first try.

Most of the SD card sockets have a pin to detect the presence of the card. This pin is usually connected to GND pin or some other pin. You can use this to generate interrupt whenever a card is inserted or removed.

When inserted, run card initialization sequence followed by FATFS_LinkDriver() and f_mount. When removed, you need to call FATFS_UnLinkDriver() to clear the disk state.


This hot-plugging does not work however for USB MSD interface. You have to insert the card before you plug the device to the USB port of the host system. And do not remove the card during USB operation.

>> source code <<

Labels:

Comments

  1. kaceejaelea5 March 2022 at 04:33

    Tips to Improve Your Smoky Habanero - TITNIA
    You ford titanium ecosport can't titanium banger get titanium body armor enough of a titanium or ceramic flat iron spicy habanero that's a scorching hot pepper. Just titanium wheels let it burn like it's a ghost pepper!

    ReplyDelete

Post a Comment

Popular posts from this blog

A Simple STM32 Example Project

Most of the embedded projects share certain initial steps. You need to confirm the clock settings before doing anything, then you want to have debug connection via a UART channel since it is cheap  but still it can provide useful information for debugging. Let us start with CubeMX. You select a device/board of your choice, set up the pinouts for one GPIO output and one UART port. Configure the clock if necessary then create a project. Clock Checking using SysTick The sanity of the clock setting can be done by checking the SysTick interval. All Cortex-M series core have SysTick timer by default, which should fire at 1msec interval while the MCU is active. In the STM32Cube, the SysTick is initialized by HAL_Init() call, which in turn calls SysTick_Config() in CMSIS. Once the SysTick is initialized, it generates 1 msec interrupt and this interrupt is handled by SysTick_Handler() according to the Cube framework. Source file 1 /** 2 * @brief This function handles
Post a Comment
Read more

STM32 USB MSC Device with FLASH memory

USB Mass Storage Class framework implements bulk-only-transfer (BOT) with SCSI protocol. USB packets from the host eventually converted SCSI transport commands by the middleware, in which data is exchanged (read / write) in the unit of logical block, typically 512 bytes. This SCSI commands works well with SD card system where a dedicated controller does the job of managing the actual memory elements. If you want to use a FLASH chip as a memory unit instead, you need to handle read / write operation directly. Fortunately, most of flash memory support 4KB block erase. This makes the 4096 bytes as a natural choice for the size of the logical block in the file usbd_storage_if.c. In this case, 8Mbit Flash memory was used. During initial enumeration, this information is registered to the host. The middleware maintains one logical block size of buffer and handles USB transaction where each payload is only 64 bytes. It then calls SCSI requests to store / retrieve data to / from physical
Post a Comment
Read more