- Ethernet Emulation Model (EEM) basics added

CMakeLists.txt

@@ -4,6 +4,9 @@ target_sources(
 
     class/cdc.c
     class/cdc.h
+    class/eem.c
+    class/eem.h
+
     CMakeLists.txt
 
     desc/usb_desc.c

class/eem.c

@@ -0,0 +1,39 @@
+#include "eem.h"
+
+#include <memory.h>
+
+#include "../usb.h"
+
+static USB_EemState eems = {0};
+
+void usb_eem_init(uint8_t data_ep) {
+    // clear the state
+    memset(&eems, 0, sizeof(USB_EemState));
+
+    // store data endpoint number
+    eems.data_ep = data_ep;
+
+    // EEM is operational
+    eems.initialized = true;
+}
+
+int usb_eem_process_and_return(USB_CallbackEvent *cbevt) {
+    switch (cbevt->type) {
+    case USB_CBEVT_UNKNOWN_REQ:
+        break;
+
+    case USB_CBEVT_OUT:
+        break;
+
+    case USB_CBEVT_IN:
+        if (cbevt->ep == eems.data_ep) { // verify endpoint number
+            usbcore_write(eems.data_ep, NULL, 0); // send ZLP
+        }
+        break;
+
+    default:
+        break;
+    }
+
+    return 0;
+}

class/eem.h

@@ -0,0 +1,26 @@
+#ifndef CLASS_EEM
+#define CLASS_EEM
+
+#include <stdint.h>
+
+#include "../usb_callback_event.h"
+
+typedef struct {
+    uint8_t data_ep; // bulk data in and out endpoint pair
+    bool initialized; // EEM is initialized
+} USB_EemState;
+
+/**
+ * Initialize USB EEM module.
+ * @param data_ep data endpoint number
+*/
+void usb_eem_init(uint8_t data_ep);
+
+/**
+ * Callback function for data reception and transmission.
+ * @param cbevt pointer to callback event structure
+ * @return function returns how to proceed with packet processing 
+*/
+int usb_eem_process_and_return(USB_CallbackEvent * cbevt);
+
+#endif /* CLASS_EEM */