LPC1754 usb mass storage

jalilisahar — Wed, 10 Dec 2025 05:04:51 GMT

I have designed a board with LPC1754 and connected a nor flash W25Q64 to it via spi. As the nor flash is not formatable to FAT16 with cmsis FileSystem, I used chan's FatFs in my project and added keil mdk usb device mass storage with cmsis driver. While connecting to pc shows device descriptor correctly and Ii is recognized as a mass storage device but windows can not specify number of disk sectors correctly. Formating and exploring it is not possible.

I have formatted it within a firmware with f_mkfs function and I am almost sure that chan's FatFs works correctly in my project.

I wonder to know if someone have any related experience?

Re: LPC1754 usb mass storage

Alice_Yang — Thu, 11 Dec 2025 03:51:06 GMT

Hello @jalilisahar

Maybe the following is one possible reason. Please check.

Windows USB Mass Storage Class (MSC) expects the logical block size to be 512 bytes by default.

Your W25Q64 is a NOR Flash (64 Mbit = 8 MB) with the following physical characteristics:

Page = 256 bytes Erase Sector = 4 KB

If the SCSI READ CAPACITY (10) command in USB MSC does not return a block length of 512 bytes, or if the FatFs diskio layer does not abstract the media as 512-byte sectors, Windows will not be able to calculate the total number of disk sectors correctly.

Alice

HardwareのトピックLPC1754 usb mass storage

LPC1754 usb mass storage

Re: LPC1754 usb mass storage