UM10503
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User manual
Rev. 1.3 — 6 July 2012
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NXP Semiconductors
UM10503
Chapter 25: LPC43xx USB API
MSC_Read
void(*void(* USBD_MSC_INIT_PARAM::MSC_Read)(uint32_t offset, uint8_t **dst, uint32_t length))(uint32_t
offset, uint8_t **dst, uint32_t length)
MSC Read callback function.
This function is provided by the application software. This function gets called when host
sends a read command.
Parameters:
1. offset = Source start address.
2. dst = Pointer to a pointer to the source of data. The MSC function drivers implemented in
stack are written with zero-copy model. Meaning the stack doesn't make an extra copy of
buffer before writing/reading data from USB hardware FIFO. Hence the parameter is
pointer to a pointer containing address buffer (uint8_t** dst). So that the user application
can update the buffer pointer instead of copying data to address pointed by the
parameter. /note The updated buffer address should be accessible by USB DMA master.
If user doesn't want to use zero-copy model, then the user should copy data to the
address pointed by the passed buffer pointer parameter and shouldn't change the
address value. See Zero-Copy Data Transfer model for more details on zero-copy
concept.
3. length = Number of bytes to be read.
Returns:
Nothing.
Table 528. USBD_MSC_INIT_PARAM class structure
Member
Description
