Merge branch 'bug/usb-full-ep'

This resolves issues related to sending full (64B) packets via USB
2.0. In this case, some hosts continue to expect more data. Add
infrastructure for sending 0-byte packets to signal end of
transmission, and use it in SerialUSB.

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/wirish/usb_serial.cpp b/wirish/usb_serial.cpp
index 380f197..d21766f 100644
--- a/wirish/usb_serial.cpp
+++ b/wirish/usb_serial.cpp
@@ -92,13 +92,24 @@ void USBSerial::write(const void *buf, uint32 len) {
     uint32 old_txed = 0;
     uint32 start = millis();
 
+    uint32 sent = 0;
+
     while (txed < len && (millis() - start < USB_TIMEOUT)) {
-        txed += usb_cdcacm_tx((const uint8*)buf + txed, len - txed);
+        sent = usb_cdcacm_tx((const uint8*)buf + txed, len - txed);
+        txed += sent;
         if (old_txed != txed) {
             start = millis();
         }
         old_txed = txed;
     }
+
+
+    if (sent == USB_CDCACM_TX_EPSIZE) {
+        while (usb_cdcacm_is_transmitting() != 0) {
+        }
+        /* flush out to avoid having the pc wait for more data */
+        usb_cdcacm_tx(NULL, 0);
+    }
 }
 
 uint32 USBSerial::available(void) {