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stmhal: Fix 64-byte USB packet bug properly. 

A 64-byte packet is now followed by a 0-byte packet if there is nothing
more to send.  This flushes the USB endpoint.
This commit is contained in:
Damien George 2014-04-17 00:12:07 +01:00
parent 28817725fc
commit efc22e376f
1 changed files with 11 additions and 10 deletions
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21
stmhal/usbd_cdc_interface.c
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@ -63,6 +63,7 @@ static uint16_t UserTxBufPtrIn = 0; // increment this pointer modulo APP_TX_DATA
static __IO uint16_t UserTxBufPtrOut = 0; // increment this pointer modulo APP_TX_DATA_SIZE when data is drained
static uint16_t UserTxBufPtrOutShadow = 0; // shadow of above
static uint8_t UserTxBufPtrWaitCount = 0; // used to implement a timeout waiting for low-level USB driver
static uint8_t UserTxNeedEmptyPacket = 0; // used to flush the USB IN endpoint if the last packet was exactly the endpoint packet size
static int user_interrupt_char = VCP_CHAR_NONE;
static void *user_interrupt_data = NULL;
@ -257,7 +258,7 @@ void USBD_CDC_HAL_TIM_PeriodElapsedCallback(void) {
return;
}
if (UserTxBufPtrOut == UserTxBufPtrIn) {
if (UserTxBufPtrOut == UserTxBufPtrIn && !UserTxNeedEmptyPacket) {
// No outstanding data to send
return;
}
@ -278,7 +279,7 @@ void USBD_CDC_HAL_TIM_PeriodElapsedCallback(void) {
UserTxBufPtrOut = UserTxBufPtrOutShadow;
}
if (UserTxBufPtrOutShadow != UserTxBufPtrIn) {
if (UserTxBufPtrOutShadow != UserTxBufPtrIn || UserTxNeedEmptyPacket) {
uint32_t buffptr;
uint32_t buffsize;
@ -290,14 +291,6 @@ void USBD_CDC_HAL_TIM_PeriodElapsedCallback(void) {
buffptr = UserTxBufPtrOutShadow;
// dpgeorge: For some reason that I don't understand, a packet size of 64 bytes
// (CDC_DATA_FS_MAX_PACKET_SIZE) does not get through to the USB host until the
// next packet is sent. To work around this, we just make sure that we never
// send a packet 64 bytes in length.
if (buffsize == CDC_DATA_FS_MAX_PACKET_SIZE) {
buffsize -= 1;
}
USBD_CDC_SetTxBuffer(&hUSBDDevice, (uint8_t*)&UserTxBuffer[buffptr], buffsize);
if (USBD_CDC_TransmitPacket(&hUSBDDevice) == USBD_OK) {
@ -306,6 +299,14 @@ void USBD_CDC_HAL_TIM_PeriodElapsedCallback(void) {
UserTxBufPtrOutShadow = 0;
}
UserTxBufPtrWaitCount = 0;
// According to the USB specification, a packet size of 64 bytes (CDC_DATA_FS_MAX_PACKET_SIZE)
// gets held at the USB host until the next packet is sent. This is because a
// packet of maximum size is considered to be part of a longer chunk of data, and
// the host waits for all data to arrive (ie, waits for a packet < max packet size).
// To flush a packet of exactly max packet size, we need to send a zero-size packet.
// See eg http://www.cypress.com/?id=4&rID=92719
UserTxNeedEmptyPacket = (buffsize == CDC_DATA_FS_MAX_PACKET_SIZE && UserTxBufPtrOutShadow == UserTxBufPtrIn);
}
}
}