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Commit 3b447ede authored by Damien George's avatar Damien George
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stmhal/usbd_cdc_interface: Change CDC RX to use a circular buffer. 

This should be a little more efficient (since we anyway scan the input
packet for the interrupt char), and it should also fix any non-atomic read
issues with the buffer state being changed during an interrupt.

Throughput tests show that RX rate is unchanged by this patch.
parent 9a8e7f7a
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stmhal/usbd_cdc_interface.c
View file @ 3b447ede
......@@ -61,7 +61,7 @@
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
#define APP_RX_DATA_SIZE 1024 // I think this must be at least CDC_DATA_FS_OUT_PACKET_SIZE=64 (APP_RX_DATA_SIZE was 2048)
#define APP_RX_DATA_SIZE 1024 // this must be 2 or greater, and a power of 2
#define APP_TX_DATA_SIZE 1024 // I think this can be any value (was 2048)
/* Private macro -------------------------------------------------------------*/
......@@ -69,9 +69,10 @@
static __IO uint8_t dev_is_connected = 0; // indicates if we are connected
static uint8_t UserRxBuffer[APP_RX_DATA_SIZE]; // received data from USB OUT endpoint is stored in this buffer
static uint16_t UserRxBufCur = 0; // points to next available character in UserRxBuffer
static uint16_t UserRxBufLen = 0; // counts number of valid characters in UserRxBuffer
static uint8_t cdc_rx_packet_buf[CDC_DATA_FS_MAX_PACKET_SIZE]; // received data from USB OUT endpoint is stored in this buffer
static uint8_t cdc_rx_user_buf[APP_RX_DATA_SIZE]; // received data is buffered here until the user reads it
static volatile uint16_t cdc_rx_buf_put = 0; // circular buffer index
static uint16_t cdc_rx_buf_get = 0; // circular buffer index
static uint8_t UserTxBuffer[APP_TX_DATA_SIZE]; // data for USB IN endpoind is stored in this buffer
static uint16_t UserTxBufPtrIn = 0; // increment this pointer modulo APP_TX_DATA_SIZE when new data is available
......@@ -141,10 +142,10 @@ static int8_t CDC_Itf_Init(void)
/*##-5- Set Application Buffers ############################################*/
USBD_CDC_SetTxBuffer(&hUSBDDevice, UserTxBuffer, 0);
USBD_CDC_SetRxBuffer(&hUSBDDevice, UserRxBuffer);
USBD_CDC_SetRxBuffer(&hUSBDDevice, cdc_rx_packet_buf);
UserRxBufCur = 0;
UserRxBufLen = 0;
cdc_rx_buf_put = 0;
cdc_rx_buf_get = 0;
return (USBD_OK);
}
......@@ -313,7 +314,7 @@ void HAL_PCD_SOFCallback(PCD_HandleTypeDef *hpcd) {
* @param Buf: Buffer of data received
* @param Len: Number of data received (in bytes)
* @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL
* @note The buffer we are passed here is just UserRxBuffer, so we are
* @note The buffer we are passed here is just cdc_rx_packet_buf, so we are
* free to modify it.
*/
static int8_t CDC_Itf_Receive(uint8_t* Buf, uint32_t *Len) {
......@@ -322,54 +323,23 @@ static int8_t CDC_Itf_Receive(uint8_t* Buf, uint32_t *Len) {
HAL_UART_Transmit_DMA(&UartHandle, Buf, *Len);
#endif
// TODO improve this function to implement a circular buffer
// if we have processed all the characters, reset the buffer counters
if (UserRxBufCur > 0 && UserRxBufCur >= UserRxBufLen) {
memmove(UserRxBuffer, UserRxBuffer + UserRxBufLen, *Len);
UserRxBufCur = 0;
UserRxBufLen = 0;
}
uint32_t delta_len;
if (mp_interrupt_char == -1) {
// no special interrupt character
delta_len = *Len;
} else {
// filter out special interrupt character from the buffer
bool char_found = false;
uint8_t *dest = Buf;
uint8_t *src = Buf;
uint8_t *buf_top = Buf + *Len;
for (; src < buf_top; src++) {
if (*src == mp_interrupt_char) {
char_found = true;
// raise KeyboardInterrupt when interrupts are finished
pendsv_kbd_intr();
} else {
if (char_found) {
*dest = *src;
}
dest++;
// copy the incoming data into the circular buffer
for (uint8_t *src = Buf, *top = Buf + *Len; src < top; ++src) {
if (mp_interrupt_char != -1 && *src == mp_interrupt_char) {
pendsv_kbd_intr();
} else {
uint16_t next_put = (cdc_rx_buf_put + 1) & (APP_RX_DATA_SIZE - 1);
if (next_put == cdc_rx_buf_get) {
// overflow, we just discard the rest of the chars
break;
}
cdc_rx_user_buf[cdc_rx_buf_put] = *src;
cdc_rx_buf_put = next_put;
}
// length of remaining characters
delta_len = dest - Buf;
}
if (UserRxBufLen + delta_len + CDC_DATA_FS_MAX_PACKET_SIZE > APP_RX_DATA_SIZE) {
// if we keep this data then the buffer can overflow on the next USB rx
// so we don't increment the length, and throw this data away
} else {
// data fits, leaving room for another CDC_DATA_FS_OUT_PACKET_SIZE
UserRxBufLen += delta_len;
}
// initiate next USB packet transfer, to append to existing data in buffer
USBD_CDC_SetRxBuffer(&hUSBDDevice, UserRxBuffer + UserRxBufLen);
// initiate next USB packet transfer
USBD_CDC_SetRxBuffer(&hUSBDDevice, cdc_rx_packet_buf);
USBD_CDC_ReceivePacket(&hUSBDDevice);
return USBD_OK;
......@@ -463,7 +433,11 @@ void USBD_CDC_TxAlways(const uint8_t *buf, uint32_t len) {
// Returns number of bytes in the rx buffer.
int USBD_CDC_RxNum(void) {
return UserRxBufLen - UserRxBufCur;
int32_t rx_waiting = (int32_t)cdc_rx_buf_put - (int32_t)cdc_rx_buf_get;
if (rx_waiting < 0) {
rx_waiting += APP_RX_DATA_SIZE;
}
return rx_waiting;
}
// timout in milliseconds.
......@@ -473,7 +447,7 @@ int USBD_CDC_Rx(uint8_t *buf, uint32_t len, uint32_t timeout) {
for (uint32_t i = 0; i < len; i++) {
// Wait until we have at least 1 byte to read
uint32_t start = HAL_GetTick();
while (UserRxBufLen == UserRxBufCur) {
while (cdc_rx_buf_put == cdc_rx_buf_get) {
// Wraparound of tick is taken care of by 2's complement arithmetic.
if (HAL_GetTick() - start >= timeout) {
// timeout
......@@ -487,7 +461,8 @@ int USBD_CDC_Rx(uint8_t *buf, uint32_t len, uint32_t timeout) {
}
// Copy byte from device to user buffer
buf[i] = UserRxBuffer[UserRxBufCur++];
buf[i] = cdc_rx_user_buf[cdc_rx_buf_get];
cdc_rx_buf_get = (cdc_rx_buf_get + 1) & (APP_RX_DATA_SIZE - 1);
}
// Success, return number of bytes read
......
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