usbd_rom_msc_ram example shows wrong disk size while connecting it to PC

[lpcware]

Content originally posted in LPCWare by Idanba on Tue Feb 10 23:41:11 MST 2015
Hi,

I'm using Keil's MCB4300 eval board and trying to run the above lpcopen example.
I can see in the code that MSC_MEM_DISK_SIZE   is defined to  be ((uint32_t) (32 * 1024)) and while trying to format it ( From the PC) the size shown
is really 32KB, BUT right clicking on the mass storage device and then properties reveals the PC recognize it as 12KB.... Why is that ?
Tried to change the MSC_MEM_DISK_SIZE  but still no change.
I'm using windows 7 and LPCXpresso v7.5.0

Thanks in advance,
Idan

[lpcware]

Content originally posted in LPCWare by Idanba on Wed Feb 25 23:16:49 MST 2015
Thanks mc !

[lpcware]

Content originally posted in LPCWare by mc on Thu Feb 12 09:24:00 MST 2015
Hi Idanba,
You can store data in a buffer in the internal SRAM as done in the example. You can also increase buffer size and transfer data from SRAM to flash when it gets fill.

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Another question I have is In case we'd like to be a mass storage DEVICE, using USB ROM API, Do we have to store the data received only on RAM?

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You will have to use IAP to program data in the flash

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where g_memDiskArea located on chip's SRAM.

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It is in internal SRAM at 0x20004000

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Is there a way to use the USB ROM API provided but define the 'Storage' as external RAM or External flash? How would these write/read function should look like?

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Yes, define buffer at external SRAM location, instead of internal SRAM. You will have to use  programming algorithm to program data in an External Flash

[lpcware]

Content originally posted in LPCWare by Idanba on Thu Feb 12 02:08:47 MST 2015
Hi Wouter,

Thanks a lot for the quick answer!

Another question I have is In case we'd like to be a mass storage DEVICE, using USB ROM API, Do we have to store the data received only on RAM?
From the example given it looks like *buff_adr will only hold the address we'd like to write into rather than data itself and this address, if I understand it right, must be accessible
for the USB DMA.

static void translate_wr(uint32_t offset, uint8_t * *buff_adr, uint32_t length, uint32_t hi_offset)
{
*buff_adr =  &g_memDiskArea[(((uint64_t) offset) | (((uint64_t) hi_offset) << 32)) + length];
}
where g_memDiskArea located on chip's SRAM.

Is there a way to use the USB ROM API provided but define the 'Storage' as external RAM or External flash? How would these write/read function should look like?

Thanks again!
Idan

[lpcware]

Content originally posted in LPCWare by Wouter on Wed Feb 11 09:56:33 MST 2015
Hi Idan,

The physical memory of the 'drive' is 32kB, but the FAT table already takes ~20kB of that, leaving ~12kB of usable space. This usable space is what Windows reports.

Regards,
Wouter