diff --git a/hw/usb_interface/ch552_fw/Makefile b/hw/usb_interface/ch552_fw/Makefile
index 71d8183..619b4a8 100644
--- a/hw/usb_interface/ch552_fw/Makefile
+++ b/hw/usb_interface/ch552_fw/Makefile
@@ -1,37 +1,88 @@
-TARGET = usb_device_cdc
+#######################################################
 
-CH554_SDCC=~/ch554_sdcc/
-CHPROG=chprog
+# Toolchain
+CC = sdcc
+OBJCOPY = objcopy
+PACK_HEX = packihx
+CHPROG = chprog
 
-# Adjust the XRAM location and size to leave space for the USB DMA buffers
-# Buffer layout in XRAM:
-# 0x0000 Ep0Buffer[8]
-# 0x0040 Ep1Buffer[8]
-# 0x0080 EP2Buffer[2*64]
-#
-# This takes a total of 256bytes, so there are 768 bytes left.
-#XRAM_SIZE = 0x0300
-#XRAM_LOC  = 0x0100
+#######################################################
 
-XRAM_SIZE = 0x0400
-XRAM_LOC  = 0x0000
+TARGET = usb_device
 
-FREQ_SYS = 16000000
+ROOT_DIR = $(dir $(abspath $(lastword $(MAKEFILE_LIST))))
+
+XRAM_SIZE = 0x0400   # 1 KB on-chip xRAM
+XRAM_LOC  = 0x0000   # xRAM area starts at address 0 in the External Data Address Space
+CODE_SIZE = 0x3800   # 14 KB program storage area
+FREQ_SYS  = 16000000 # 16 MHz system clock
+
+EXTRA_FLAGS = -DBUILD_CODE
+
+CFLAGS = \
+         -V \
+         -mmcs51 \
+         --model-small \
+         --xram-size $(XRAM_SIZE) \
+         --xram-loc $(XRAM_LOC) \
+         --code-size $(CODE_SIZE) \
+         -I$(ROOT_DIR)include \
+         -DFREQ_SYS=$(FREQ_SYS) \
+         $(EXTRA_FLAGS)
+
+LFLAGS = \
+         $(CFLAGS)
+
+C_FILES = \
+          main.c \
+          include/debug.c \
+          include/print.c
+
+# Create a .rel file for each .c file
+RELS = $(C_FILES:.c=.rel)
+
+%.rel : %.c
+	$(CC) -c $(CFLAGS) $<
 
 usb_strings.h: encode_usb_strings.py
 	./encode_usb_strings.py
 
-C_FILES = \
-	main.c \
-	include/debug.c \
-	include/print.c
+# Note: SDCC will dump all of the temporary files into this one,
+# so strip the paths from RELS
+# For now, get around this by stripping the paths off of the RELS list.
 
-pre-flash:
+$(TARGET).ihx: $(RELS)
+	$(CC) $(notdir $(RELS)) $(LFLAGS) -o $(TARGET).ihx
 
+$(TARGET).hex: $(TARGET).ihx
+	$(PACK_HEX) $(TARGET).ihx > $(TARGET).hex
 
-flash_patched: usb_device_cdc.bin
-	./inject_serial_number.py -i usb_device_cdc.bin -o patched.bin
-	${CHPROG} patched.bin
+$(TARGET).bin: $(TARGET).ihx
+	$(OBJCOPY) -I ihex -O binary $(TARGET).ihx $(TARGET).bin
+
+flash: $(TARGET).bin
+	$(CHPROG) $(TARGET).bin
+
+flash_patched: $(TARGET).bin
+	./inject_serial_number.py -i $(TARGET).bin -o patched.bin
+	$(CHPROG) patched.bin
 	rm patched.bin
 
-include Makefile.include
+.DEFAULT_GOAL := all
+all: $(TARGET).bin $(TARGET).hex
+
+clean:
+	rm -f \
+	$(notdir $(RELS:.rel=.asm)) \
+	$(notdir $(RELS:.rel=.lst)) \
+	$(notdir $(RELS:.rel=.mem)) \
+	$(notdir $(RELS:.rel=.rel)) \
+	$(notdir $(RELS:.rel=.rst)) \
+	$(notdir $(RELS:.rel=.sym)) \
+	$(notdir $(RELS:.rel=.adb)) \
+	$(TARGET).lk \
+	$(TARGET).map \
+	$(TARGET).mem \
+	$(TARGET).ihx \
+	$(TARGET).hex \
+	$(TARGET).bin
diff --git a/hw/usb_interface/ch552_fw/Makefile.include b/hw/usb_interface/ch552_fw/Makefile.include
deleted file mode 100644
index d4f7a8c..0000000
--- a/hw/usb_interface/ch552_fw/Makefile.include
+++ /dev/null
@@ -1,70 +0,0 @@
-#######################################################
-
-# toolchain
-CC = sdcc
-OBJCOPY = objcopy
-PACK_HEX = packihx
-WCHISP ?= wchisptool -g -f
-
-#######################################################
-
-EXTRA_FLAGS = -D BUILD_CODE
-
-FREQ_SYS ?= 24000000
-
-XRAM_SIZE ?= 0x0400
-
-XRAM_LOC ?= 0x0000
-
-CODE_SIZE ?= 0x3800
-
-ROOT_DIR := $(dir $(abspath $(lastword $(MAKEFILE_LIST))))
-
-CFLAGS := -V -mmcs51 --model-small \
-	--xram-size $(XRAM_SIZE) --xram-loc $(XRAM_LOC) \
-	--code-size $(CODE_SIZE) \
-	-I$(ROOT_DIR)include -DFREQ_SYS=$(FREQ_SYS) \
-	$(EXTRA_FLAGS)
-
-LFLAGS := $(CFLAGS)
-
-RELS := $(C_FILES:.c=.rel)
-
-print-%  : ; @echo $* = $($*)
-
-%.rel : %.c
-	$(CC) -c $(CFLAGS) $<
-
-# Note: SDCC will dump all of the temporary files into this one, so strip the paths from RELS
-# For now, get around this by stripping the paths off of the RELS list.
-
-$(TARGET).ihx: $(RELS)
-	$(CC) $(notdir $(RELS)) $(LFLAGS) -o $(TARGET).ihx
-
-$(TARGET).hex: $(TARGET).ihx
-	$(PACK_HEX) $(TARGET).ihx > $(TARGET).hex
-
-$(TARGET).bin: $(TARGET).ihx
-	$(OBJCOPY) -I ihex -O binary $(TARGET).ihx $(TARGET).bin
-	
-flash: $(TARGET).bin pre-flash
-	$(WCHISP) $(TARGET).bin
-
-.DEFAULT_GOAL := all
-all: $(TARGET).bin $(TARGET).hex
-
-clean:
-	rm -f \
-	$(notdir $(RELS:.rel=.asm)) \
-	$(notdir $(RELS:.rel=.lst)) \
-	$(notdir $(RELS:.rel=.mem)) \
-	$(notdir $(RELS:.rel=.rel)) \
-	$(notdir $(RELS:.rel=.rst)) \
-	$(notdir $(RELS:.rel=.sym)) \
-	$(notdir $(RELS:.rel=.adb)) \
-	$(TARGET).lk \
-	$(TARGET).map \
-	$(TARGET).mem \
-	$(TARGET).ihx \
-	$(TARGET).hex \
-	$(TARGET).bin
diff --git a/hw/usb_interface/ch552_fw/baud rate calculator.ods b/hw/usb_interface/ch552_fw/baud rate calculator.ods
deleted file mode 100644
index e3ec753..0000000
Binary files a/hw/usb_interface/ch552_fw/baud rate calculator.ods and /dev/null differ
diff --git a/hw/usb_interface/ch552_fw/encode_usb_strings.py b/hw/usb_interface/ch552_fw/encode_usb_strings.py
index 151d2f6..697514e 100755
--- a/hw/usb_interface/ch552_fw/encode_usb_strings.py
+++ b/hw/usb_interface/ch552_fw/encode_usb_strings.py
@@ -20,37 +20,51 @@ def descriptor_to_string(descriptor):
 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.append(0x00) # Placeholder for length
+    descriptor.append(0x03) # Descriptor type (String)
     descriptor.extend(string.encode('utf-16')[2:]) # crop the BOM
-    descriptor[0] = len(descriptor)
+    descriptor[0] = len(descriptor) # Set length of this descriptor (in bytes)
 
     return bytes(descriptor)
 
+def format_descriptor(name, value):
+    descriptor = string_to_descriptor(value)
+    formatted = [
+        'unsigned char FLASH {}[] = {{  // "{}"'.format(name, value),  # Add string as a comment
+        '    {},    // Length of this descriptor (in bytes)'.format(descriptor[0]),
+        '    0x03,  // Descriptor type (String)'
+    ]
+
+    formatted.extend(
+        [
+            '    ' + ', '.join(
+                ["'{}', 0".format(chr(b)) if b != 0x00 else "0x00" for b in descriptor[2 + i:2 + i + 8:2]]
+            ) + ','
+            for i in range(0, len(descriptor[2:]), 8)  # 8 bytes = 4 characters
+        ]
+    )
+    formatted.append('};\n')
+    return '\n'.join(formatted)
 
 if __name__ == "__main__":
-    manufacturer = 'Tillitis'
-    product = 'MTA1-USB-V1'
-    serial = "68de5d27-e223-4874-bc76-a54d6e84068f"
+    strings = {
+        "ProdDesc": "MTA1-USB-V1",
+        "ManufDesc": "Tillitis",
+        "SerialDesc": "68de5d27-e223-4874-bc76-a54d6e84068f",
+        "CdcCtrlInterfaceDesc": "CDC-Ctrl",
+        "CdcDataInterfaceDesc": "CDC-Data",
+        "FidoHidInterfaceDesc": "FIDO-HID",
+        "TkeyCtrlInterfaceDesc": "TKEY-Ctrl"
+    }
+
+    with open('include/usb_strings.h', 'w') as f:
+        f.write('#ifndef __USB_STRINGS_H__\n')
+        f.write('#define __USB_STRINGS_H__\n')
+        f.write('\n')
+        f.write('#include "mem.h"\n')
+        f.write('\n')
+
+        for name, value in strings.items():
+            f.write(format_descriptor(name, value) + '\n')
 
-    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 ProdDesc[]={{  // "{}"\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 ManufDesc[]={{  // "{}"\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 SerialDesc[]={{  // "{}"\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')
diff --git a/hw/usb_interface/ch552_fw/include/debug.h b/hw/usb_interface/ch552_fw/include/debug.h
index ff406c7..1e443b3 100644
--- a/hw/usb_interface/ch552_fw/include/debug.h
+++ b/hw/usb_interface/ch552_fw/include/debug.h
@@ -186,6 +186,8 @@ inline uint8_t  CH554UART1RcvByte( )
  *******************************************************************************/
 inline void CH554UART1SendByte(uint8_t SendDat)
 {
+    while(gpio_p1_4_get() == 0)
+        ;
     SBUF1 = SendDat; // Query sending, the interrupt mode does not need the following two statements, but TI=0 is required before sending
     while (U1TI == 0)
         ;
diff --git a/hw/usb_interface/ch552_fw/include/usb_strings.h b/hw/usb_interface/ch552_fw/include/usb_strings.h
index a36d512..2302329 100644
--- a/hw/usb_interface/ch552_fw/include/usb_strings.h
+++ b/hw/usb_interface/ch552_fw/include/usb_strings.h
@@ -3,22 +3,22 @@
 
 #include "mem.h"
 
-unsigned char FLASH ProdDesc[]={  // "MTA1-USB-V1"
+unsigned char FLASH ProdDesc[] = {  // "MTA1-USB-V1"
     24,    // Length of this descriptor (in bytes)
     0x03,  // Descriptor type (String)
     'M', 0, 'T', 0, 'A', 0, '1', 0,
     '-', 0, 'U', 0, 'S', 0, 'B', 0,
-    '-', 0, 'V', 0, '1', 0
+    '-', 0, 'V', 0, '1', 0,
 };
 
-unsigned char FLASH ManufDesc[]={  // "Tillitis"
+unsigned char FLASH ManufDesc[] = {  // "Tillitis"
     18,    // Length of this descriptor (in bytes)
     0x03,  // Descriptor type (String)
     'T', 0, 'i', 0, 'l', 0, 'l', 0,
-    'i', 0, 't', 0, 'i', 0, 's', 0
+    'i', 0, 't', 0, 'i', 0, 's', 0,
 };
 
-unsigned char FLASH SerialDesc[]={  // "68de5d27-e223-4874-bc76-a54d6e84068f"
+unsigned char FLASH SerialDesc[] = {  // "68de5d27-e223-4874-bc76-a54d6e84068f"
     74,    // Length of this descriptor (in bytes)
     0x03,  // Descriptor type (String)
     '6', 0, '8', 0, 'd', 0, 'e', 0,
@@ -32,28 +32,28 @@ unsigned char FLASH SerialDesc[]={  // "68de5d27-e223-4874-bc76-a54d6e84068f"
     '0', 0, '6', 0, '8', 0, 'f', 0,
 };
 
-unsigned char FLASH CdcCtrlInterfaceDesc[] = {
+unsigned char FLASH CdcCtrlInterfaceDesc[] = {  // "CDC-Ctrl"
     18,    // Length of this descriptor (in bytes)
     0x03,  // Descriptor type (String)
     'C', 0, 'D', 0, 'C', 0, '-', 0,
     'C', 0, 't', 0, 'r', 0, 'l', 0,
 };
 
-unsigned char FLASH CdcDataInterfaceDesc[] = {
+unsigned char FLASH CdcDataInterfaceDesc[] = {  // "CDC-Data"
     18,    // Length of this descriptor (in bytes)
     0x03,  // Descriptor type (String)
     'C', 0, 'D', 0, 'C', 0, '-', 0,
     'D', 0, 'a', 0, 't', 0, 'a', 0,
 };
 
-unsigned char FLASH FidoHidInterfaceDesc[] = {
+unsigned char FLASH FidoHidInterfaceDesc[] = {  // "FIDO-HID"
     18,    // Length of this descriptor (in bytes)
     0x03,  // Descriptor type (String)
     'F', 0, 'I', 0, 'D', 0, 'O', 0,
     '-', 0, 'H', 0, 'I', 0, 'D', 0,
 };
 
-unsigned char FLASH TkeyCtrlInterfaceDesc[] = {
+unsigned char FLASH TkeyCtrlInterfaceDesc[] = {  // "TKEY-Ctrl"
     20,    // Length of this descriptor (in bytes)
     0x03,  // Descriptor type (String)
     'T', 0, 'K', 0, 'E', 0, 'Y', 0,
diff --git a/hw/usb_interface/ch552_fw/main.c b/hw/usb_interface/ch552_fw/main.c
index 1bfbe6d..33277a9 100644
--- a/hw/usb_interface/ch552_fw/main.c
+++ b/hw/usb_interface/ch552_fw/main.c
@@ -27,7 +27,6 @@ uint16_t SetupLen = 0;
 uint8_t SetupReq = 0;
 uint8_t UsbConfig = 0;
 const uint8_t *pDescr = NULL;         // USB configuration flag
-USB_SETUP_REQ SetupReqBuf = { 0 };    // Temporary Setup package
 
 #define UsbSetupBuf                   ((PUSB_SETUP_REQ)Ep0Buffer)