2014-06-18 06:01 AM
Dear All,
I am implementing a solution where I have to read file when device is in usb mass storage mode and after reading I have to delete the file. I have implemented USB Mass Storage device based on STM32F105 and I am using emfile - emb OS from segger. When device in MSC, I am stuck at SD_Readbyte flag. My doubts are : 1. Is USB blocking access to SD Card/SPI lock? 2. At what point I should be able to access the SD Card? - After completion of USB MSC Initialization? Please revert ASAP. Thanking you in anticipation. Best Regards, hgaurav2014-06-18 08:06 AM
You have to disconnect the USB, or have it present that the media is ejected, changed, not present, and/or not ready. If you don't do this the contention/coherency issues are practically impossible to overcome, as you don't control enough of the software in the system.
2014-06-24 12:35 AM
2014-06-24 07:10 AM
The card reader will basically take the read, write, control functions passed as MSC/SCSI commands, and turn them into card access commands. It does this at a sector/block level.
If you have code on the STM32 that you want to access the card and files on it, you need an access layer/driver, and a file system, like FatFs. What is very difficult to do is allow a PC and STM32 access the card at the same time, you are likely to corrupt the content of the card as you have different views on what is current.