stm: Add support for ctrl-C to interrupt running Python.

Using PendSV interrupt at lowest priority, code can now raise an
exception during an interrupt by calling pendsv_nlr_jump.  The exception
will be raised when all interrupts are finished.  This is used to trap
ctrl-C from the USB VCP to break out of running Python code.

1 files changed, 5 insertions, 0 deletions

diff --git a/stm/usb.h b/stm/usb.h
index c3b39ca846..1f263bd07b 100644
--- a/stm/usb.h
+++ b/stm/usb.h
@@ -1,5 +1,10 @@
+#define VCP_CHAR_NONE   (0)
+#define VCP_CHAR_CTRL_C (3)
+#define VCP_CHAR_CTRL_D (4)
+
 void pyb_usb_dev_init(void);
 bool usb_vcp_is_enabled(void);
+void usb_vcp_set_interrupt_char(int c);
 int usb_vcp_rx_any(void);
 char usb_vcp_rx_get(void);
 void usb_vcp_send_str(const char* str);