Fix isochronous endpoints on LPC1768

Perform isochronous endpoint processing from the frame interrupt
rather than the endpoint interrupt. Isochronous endpoints to not
generate interrupts normally and are intended to be handled from
the start of frame interrupt.

Author: c1728p9

usb/device/targets/TARGET_NXP/USBHAL_LPC17.cpp

@@ -29,6 +29,9 @@
 // Convert physical endpoint number to register bit
 #define EP(endpoint) (1UL<<DESC_TO_PHY(endpoint))
 
+// Check if this is an isochronous endpoint
+#define ISO_EP(endpoint)        ((((endpoint) & 0xF) == 3) || (((endpoint) & 0xF) == 6) || (((endpoint) & 0xF) == 9) || (((endpoint) & 0xF) == 12))
+
 #define DESC_TO_PHY(endpoint) ((((endpoint)&0x0F)<<1) | (((endpoint) & 0x80) ? 1:0))
 #define PHY_TO_DESC(endpoint) (((endpoint)>>1)|(((endpoint)&1)?0x80:0))
 
@@ -122,6 +125,13 @@ static USBPhyHw *instance;
 
 static uint32_t opStarted;
 
+static const usb_ep_t ISO_EPS[] = {
+        0x03, 0x83,
+        0x06, 0x86,
+        0x09, 0x89,
+        0x0C, 0x8C
+};
+
 static void SIECommand(uint32_t command)
 {
     // The command phase of a SIE transaction
@@ -465,6 +475,9 @@ void USBPhyHw::disconnect(void)
 
     // Disconnect USB device
     SIEdisconnect();
+
+    // Reset all started operations
+    opStarted = 0;
 }
 
 void USBPhyHw::configure(void)
@@ -551,7 +564,7 @@ uint32_t USBPhyHw::endpoint_read_result(usb_ep_t endpoint)
     read_sizes[endpoint] = 0;
 
     // Don't clear isochronous endpoints
-    if ((DESC_TO_PHY(endpoint) >> 1) % 3 || (DESC_TO_PHY(endpoint) >> 1) == 0) {
+    if (!ISO_EP(endpoint)) {
         SIEselectEndpoint(endpoint);
         SIEclearBuffer();
     }
@@ -692,6 +705,20 @@ void USBPhyHw::process(void)
         events->sof(SIEgetFrameNumber());
         // Clear interrupt status flag
         LPC_USB->USBDevIntClr = FRAME;
+
+        // There is no ISO interrupt, instead a packet is transferred every SOF
+        for (uint32_t i = 0; i < sizeof(ISO_EPS) / sizeof(ISO_EPS[0]); i++) {
+            uint8_t endpoint = ISO_EPS[i];
+            if (opStarted & EP(endpoint)) {
+                opStarted &= ~EP(endpoint);
+                if (IN_EP(endpoint)) {
+                    events->in(endpoint);
+                } else {
+                    events->out(endpoint);
+                }
+            }
+        }
+
     }
 
     if (LPC_USB->USBDevIntSt & DEV_STAT) {
@@ -717,6 +744,7 @@ void USBPhyHw::process(void)
             }
             memset(read_buffers, 0, sizeof(read_buffers));
             memset(read_sizes, 0, sizeof(read_sizes));
+            opStarted = 0;
             events->reset();
         }
     }
@@ -752,12 +780,16 @@ void USBPhyHw::process(void)
             }
         }
 
-        //TODO - should probably process in the reverse order
         for (uint8_t num = 2; num < 16 * 2; num++) {
             uint8_t endpoint = PHY_TO_DESC(num);
             if (LPC_USB->USBEpIntSt & EP(endpoint)) {
                 selectEndpointClearInterrupt(endpoint);
+                if (ISO_EP(endpoint)) {
+                    // Processing for ISO endpoints done in FRAME handling
+                    continue;
+                }
                 if (opStarted & EP(endpoint)) {
+                    opStarted &= ~EP(endpoint);
                     if (IN_EP(endpoint)) {
                         events->in(endpoint);
                     } else {