Data transfer on noncontrol endpoints

UM0463

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Data transfer on noncontrol endpoints

Noncontrol endpoints are identified by the endpoint address and the endpoint direction, for

example endpoint 2 IN and endpoint 2 OUT are two different endpoints. The endpoint of IN

direction is used to send data from the device to the host. It can be either a bulk endpoint or

an interrupt endpoint. The endpoint of OUT direction is used to receive data from the host to

the device. It can be either a bulk endpoint or an interrupt endpoint too.

The library provides a set of functions for transferring data along endpoints of both

directions. Each endpoint of either direction has two functions.

4.1

Sending data to the host

There are two functions for sending data to an endpoint.

char USB_SendDataEP?( unsigned char *DataAddress,

unsigned char LengthToXmit);

char USB_EP?_isSent(void);

Where? is a digit that represents the endpoint address. The digit ranges from 1 to 5 for

ST7SCR, and the digit is 1 or 2 for ST7265. For example, the sending functions for endpoint

2 are USB_SendDataEP2() and USB_EP2_isSent().

The function USB_SendDataEP?() is used to start a sending procedure. The parameter

DataAddress is a pointer which points to the data buffer and the parameter LengthToXmit

gives the length of the data package. After the sending procedure is started, this function

returns REQ_SUCCESS to the caller immediately. The function returns REQ_ERROR if the

previous sending procedure is not finished or the specified endpoint is in the state of

DISABLE or STALL. The user code should call function USB_EP?_isSent() some time later

to enquire that the data transmission is finished. The function USB_EP?_isSent() returns a

nonzero value if the data is sent, otherwise it returns a value zero. The user code has to wait

that a sending procedure is finished before starting another sending procedure.

If the data package to be sent is longer than 255 bytes, the user code has to split the data

package into a few small pieces that shorter than 255 bytes. The length of these few small

data pieces, except the last data piece, have to be in the multiple of the maximum packet

size of the used endpoint. Refer to Section 1.2.1 for the maximum packet size of each

endpoint.

4.2

Receiving data from the host

There are two functions for receiving data from an endpoint.

char USB_RecvDataEP?(unsigned char *DataAddress,

unsigned char Length);

unsigned char USB_TakeDataEP?(void);

Where? is a digit that represents the endpoint address. The digit is 1 or 2 for ST7265 and

the digit is 2 for ST7SCR only. For example, the receiving functions for endpoint 2 are

USB_RecvDataEP2() and USB_TakeDataEP2().