small speed up using larger buffer and multipart Tx

TinyFrame/TF_Integration.c

@@ -14,8 +14,40 @@
 extern osSemaphoreId semVcomTxReadyHandle;
 extern osMutexId mutTinyFrameTxHandle;
 
+static volatile bool first_tx = false; // XXX global
+
 void TF_WriteImpl(TinyFrame *tf, const uint8_t *buff, uint32_t len)
 {
+#if 1
+//    if (!first_tx) {
+//        // wait for the last USB transmission to be finished
+//        int32_t mxStatus;
+//        mxStatus = osSemaphoreWait(semVcomTxReadyHandle, 100);
+//        if (mxStatus != osOK) {
+//            TF_Error("Tx stalled");
+//            return;
+//        }
+//    }
+//    first_tx = false;
+
+    // Padding to a multiple of 64 bytes
+    if (len&0x3F) {
+        uint32_t pad = (64 - (len&0x3F));
+        memset((void *) (buff + len), 0, pad);
+        len += pad; // padding to a multiple of 64 (size of the endpoint)
+    }
+
+    assert_param(HAL_OK == HAL_PCD_EP_Transmit(hUsbDeviceFS.pData, CDC_IN_EP, (uint8_t *) buff, len));
+
+    // Wait for the semaphore - HAL keeps a pointer to the buffer, and it's the TinyFrame Tx buffer,
+    // so if we let it process it in the background, it could get corrupted before the Tx is completed.
+    int32_t mxStatus;
+    mxStatus = osSemaphoreWait(semVcomTxReadyHandle, 100);
+    if (mxStatus != osOK) {
+        TF_Error("Tx stalled");
+        return;
+    }
+#else
     (void) tf;
 #define CHUNK 64 // same as TF_SENDBUF_LEN, so we should always have only one run of the loop
     int32_t total = (int32_t) len;
@@ -37,6 +69,7 @@ void TF_WriteImpl(TinyFrame *tf, const uint8_t *buff, uint32_t len)
         buff += chunksize;
         total -= chunksize;
     }
+#endif
 }
 
 /** Claim the TX interface before composing and sending a frame */
@@ -47,6 +80,17 @@ bool TF_ClaimTx(TinyFrame *tf)
     assert_param(!inIRQ());
 
     assert_param(osOK == osMutexWait(mutTinyFrameTxHandle, 5000));
+
+//    // wait for the last USB transmission to be finished
+//    int32_t mxStatus;
+//    mxStatus = osSemaphoreWait(semVcomTxReadyHandle, 100);
+//    if (mxStatus != osOK) {
+//        TF_Error("Tx stalled");
+//        return false;
+//    }
+
+    first_tx = true;
+
     return true;
 }