USB: move firmware for usb-to-serial MCU (CH552)

Change links to the new ch552_fw directory.

hw/usb_interface/ch552_fw/encode_usb_strings.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+
+def descriptor_to_string(descriptor):
+    """ Convert a bytes object containing a USB string descriptor into a python string"""
+    bLength = descriptor[0]
+    if bLength != len(descriptor):
+        raise Exception('Descriptor length mismatch, length_field:{} actual_length:{}'.format(
+                bLength,
+                len(descriptor)
+                ))
+
+    bDescriptorType = descriptor[1]
+    if bDescriptorType != 0x03:
+        raise Exception('Descriptor type mismatch, bDescriptorType:{02x} expected:0x03'.format(
+            bDescriptorType
+            ))
+
+    return descriptor[2:].decode('utf-16', errors='strict')
+
+def string_to_descriptor(string):
+    """ Convert a python string into a bytes object containing a USB string descriptor"""
+    descriptor = bytearray()
+    descriptor.append(0x00) # placeholder for length
+    descriptor.append(0x03)
+    descriptor.extend(string.encode('utf-16')[2:]) # crop the BOM
+    descriptor[0] = len(descriptor)
+
+    return bytes(descriptor)
+
+
+if __name__ == "__main__":
+    manufacturer = 'Tillitis'
+    product = 'MTA1-USB-V1'
+    serial = "68de5d27-e223-4874-bc76-a54d6e84068f"
+
+    with open('usb_strings.h', 'w') as f:
+        f.write('#ifndef USB_STRINGS\n')
+        f.write('#define USB_STRINGS\n')
+    
+        f.write('unsigned char __code Prod_Des[]={{  // "{}"\n'.format(product))
+        f.write('    ')
+        f.write(', '.join(['0x{:02x}'.format(i) for i in string_to_descriptor(product)]))
+        f.write('\n};\n\n')
+        
+        f.write('unsigned char __code Manuf_Des[]={{  // "{}"\n'.format(manufacturer))
+        f.write('    ')
+        f.write(', '.join(['0x{:02x}'.format(i) for i in string_to_descriptor(manufacturer)]))
+        f.write('\n};\n\n')
+    
+        f.write('unsigned char __code SerDes[]={{  // "{}"\n'.format(serial))
+        f.write('    ')
+        f.write(', '.join(['0x{:02x}'.format(i) for i in string_to_descriptor(serial)]))
+        f.write('\n};\n\n')
+    
+    
+        f.write('#endif\n')