added getDTR and getRTS to usb.h, subtly modded how sendBytes checks for connection

flip flopped back and forth on how much work should be done here. For now its like 5 lines of changes

2 files changed, 26 insertions, 6 deletions

diff --git a/libmaple/usb/usb.c b/libmaple/usb/usb.c
index 7cca37f..8dbf9c9 100644
--- a/libmaple/usb/usb.c
+++ b/libmaple/usb/usb.c
@@ -339,29 +339,39 @@ void usbWaitReset(void) {
   systemHardReset();
 }
 
+
+/* todo, change this function to behave like below */
 /* copies data out of sendBuf into the packet memory for
    usb, but waits until any previous usb transmissions have
    completed before doing this. It returns without waiting
    for its data to be sent. most efficient when 64 bytes are copied
    at a time. users responsible for not overflowing sendbuf
    with len! if > 64 bytes are being sent, then the function
-   will block at every 64 byte packet
+   will simply send the first 64 and return. It is the USERS JOB
+   to implement any blocking. return -1 implies connection failure,
+   return 0 implies buffer filled, return < len implies another
+   transaction is needed to complete the send. 
 */
+
+/* current behavior:
+   sendBytes will block until bytes are actually sent over the pipe.
+   broken pipes could stall this function. DTR and RTS are used to check
+   for a valid connection. 
+ */
 int16 usbSendBytes(uint8* sendBuf, uint16 len) {
 
-  if (((line_dtr_rts & CONTROL_LINE_RTS) == 0) || bDeviceState != CONFIGURED) {
+  if (bDeviceState != CONFIGURED || (!usbGetDTR() && !usbGetRTS())) {
     return -1; /* indicates to caller to stop trying, were not connected */
   }
 
-  /* This may be the correct behavior but it's undocumented
+    /*
   if (countTx >= VCOM_TX_EPSIZE) {
     return 0; // indicates to caller that the buffer is full 
   }
-  */
+    */
 
-  /* Block for any pending writes */
   while (countTx)
-     ;
+    ;
 
   uint16 sent = len;
 
@@ -435,3 +445,11 @@ void usbSendHello(void) {
   uint8 recv[64];
   usbReceiveBytes(&recv[0],1);
 }
+
+uint8 usbGetDTR() {
+  return ((line_dtr_rts & CONTROL_LINE_DTR) != 0);
+}
+
+uint8 usbGetRTS() {
+  return ((line_dtr_rts & CONTROL_LINE_RTS) != 0);
+}
diff --git a/libmaple/usb/usb.h b/libmaple/usb/usb.h
index ac8dc40..6451f7e 100644
--- a/libmaple/usb/usb.h
+++ b/libmaple/usb/usb.h
@@ -54,6 +54,8 @@ typedef enum
   int16 usbSendBytes(uint8* sendBuf,uint16 len);
   uint8 usbBytesAvailable(void);
   uint8 usbReceiveBytes(uint8* recvBuf, uint8 len);
+  uint8 usbGetDTR(void);
+  uint8 usbGetRTS(void);
 
   void usbSendHello(void);