Slightly improve and generify the USB infrastructure.

The good news is that <libmaple/usb.h> and <libmaple/usb_cdcacm.h> did
turn out generic enough in what they specify to go on unchanged.

However, we can't just go on assuming that there's USB just because
we're on an F1. Now that there's value line in the tree, we need to be
more careful (value line F1s don't have USB peripherals). To that end,
make all the F1 board-includes/*.mk files specify what line their MCU
is with an MCU_F1_LINE variable. Use that to hack
libmaple/usb/rules.mk so we only try to build the USB module under
appropriate circumstances.

While we're at it, add a vector_symbols.inc for value line MCUs under
support/ld/. We need this to get the target-config.mk modifications
implied by the addition of MCU_F1_LINE. We'll fix up some other
performance-line-isms under libmaple/stm32f1 in a separate commit.

Also in libmaple/usb/:

- Move everything into a new stm32f1 directory. Due to aforementioned
  rules.mk hacks, there is no immediate need for an stm32f2
  directory (USB support doesn't exist there).

- Update the README for style and content.

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

1 files changed, 4 insertions, 1 deletions

diff --git a/wirish/include/wirish/usb_serial.h b/wirish/include/wirish/usb_serial.h
index 81e9e97..f36671b 100644
--- a/wirish/include/wirish/usb_serial.h
+++ b/wirish/include/wirish/usb_serial.h
@@ -25,13 +25,14 @@
  *****************************************************************************/
 
 /**
- * @brief Wirish virtual serial port
+ * @brief Wirish USB virtual serial port (SerialUSB).
  */
 
 #ifndef _WIRISH_USB_SERIAL_H_
 #define _WIRISH_USB_SERIAL_H_
 
 #include <wirish/Print.h>
+#include <wirish/boards.h>
 
 /**
  * @brief Virtual serial terminal.
@@ -58,7 +59,9 @@ public:
     uint8 pending();
 };
 
+#if BOARD_HAVE_SERIALUSB
 extern USBSerial SerialUSB;
+#endif
 
 #endif