Discard usb output before connection. Handle USB reset.0.2

Discarding output before USB is plugged in allows threads that send output
and do other things to work without a USB connection. Unfortuantely, there
doesn't appear to be any way to detect when the USB link is disconnected,
which means that once USB is enabled, future writes will continue to block.

USB reset causes the USB interrupts to all be reconfigured back to power-on
state.

Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 22 insertions, 11 deletions

diff --git a/ao_usb.c b/ao_usb.c
index 69f87fc4..315eea08 100644
--- a/ao_usb.c
+++ b/ao_usb.c
@@ -23,7 +23,20 @@ struct ao_task __xdata ao_usb_task;
 static __xdata uint16_t	ao_usb_in_bytes;
 static __xdata uint16_t	ao_usb_out_bytes;
 static __xdata uint8_t	ao_usb_iif;
-static __xdata uint8_t	ao_usb_oif;
+static __xdata uint8_t	ao_usb_running;
+
+static void
+ao_usb_set_interrupts(void)
+{
+	/* IN interrupts on the control an IN endpoints */
+	USBIIE = (1 << AO_USB_CONTROL_EP) | (1 << AO_USB_IN_EP);
+
+	/* OUT interrupts on the OUT endpoint */
+	USBOIE = (1 << AO_USB_OUT_EP);
+
+	/* Only care about reset */
+	USBCIE = USBCIE_RSTIE;
+}
 
 /* This interrupt is shared with port 2, 
  * so when we hook that up, fix this
@@ -38,9 +51,11 @@ ao_usb_isr(void) interrupt 6
 	if (ao_usb_iif & (1 << AO_USB_IN_EP))
 		ao_wakeup(&ao_usb_in_bytes);
 
-	ao_usb_oif |= USBOIF;
-	if (ao_usb_oif & (1 << AO_USB_OUT_EP))
+	if (USBOIF & (1 << AO_USB_OUT_EP))
 		ao_wakeup(&ao_usb_out_bytes);
+
+	if (USBCIF & USBCIF_RSTIF)
+		ao_usb_set_interrupts();
 }
 
 struct ao_usb_setup {
@@ -136,6 +151,7 @@ ao_usb_ep0_queue_byte(uint8_t a)
 void
 ao_usb_set_address(uint8_t address)
 {
+	ao_usb_running = 1;
 	USBADDR = address | 0x80;
 	while (USBADDR & 0x80)
 		;
@@ -318,6 +334,8 @@ ao_usb_flush(void) __critical
 void
 ao_usb_putchar(char c) __critical
 {
+	if (!ao_usb_running)
+		return;
 	for (;;) {
 		USBINDEX = AO_USB_IN_EP;
 		if ((USBCSIL & USBCSIL_INPKT_RDY) == 0)
@@ -362,15 +380,8 @@ ao_usb_enable(void)
 
 	ao_usb_set_configuration();
 	
-	/* IN interrupts on the control an IN endpoints */
-	USBIIE = (1 << AO_USB_CONTROL_EP) | (1 << AO_USB_IN_EP);
+	ao_usb_set_interrupts();
 
-	/* OUT interrupts on the OUT endpoint */
-	USBOIE = (1 << AO_USB_OUT_EP);
-
-	/* Ignore control interrupts */
-	USBCIE = 0;
-	
 	/* enable USB interrupts */
 	IEN2 |= IEN2_USBIE;