DFU serial number - avoid reading serial from flash chip

Set a DFU mode specific serial number

firmware/hackrf-common.cmake

@@ -86,6 +86,7 @@ SET(CPUFLAGS_M4 "-mthumb -mcpu=cortex-m4 -mfloat-abi=hard -mfpu=fpv4-sp-d16")
 SET(CFLAGS_M4 "-std=gnu99 ${CFLAGS_COMMON} ${CPUFLAGS_M4} -DLPC43XX_M4")
 SET(CXXFLAGS_M4 "-std=gnu++0x ${CFLAGS_COMMON} ${CPUFLAGS_M4} -DLPC43XX_M4")
 SET(LDFLAGS_M4 "${LDFLAGS_COMMON} ${CPUFLAGS_M4} ${LDSCRIPT_M4} -Xlinker -Map=m4.map")
+SET(CFLAGS_M4_DFU "-std=gnu99 ${CFLAGS_COMMON} ${CPUFLAGS_M4} -DLPC43XX_M4 -DDFU_MODE")
 SET(LDFLAGS_M4_DFU "${LDFLAGS_COMMON} ${CPUFLAGS_M4} ${LDSCRIPT_M4_DFU} -Xlinker -Map=m4.map")
 
 set(BUILD_SHARED_LIBS OFF)
@@ -158,12 +159,10 @@ macro(DeclareTargets)
 		COMMAND ${CMAKE_OBJCOPY} -Obinary ${PROJECT_NAME}_m0.elf ${PROJECT_NAME}_m0.bin
 	)
 
-	# Object files to be linked for both DFU and SPI flash versions
+	# Object files to be linked for SPI flash versions
 	add_library(${PROJECT_NAME}_objects OBJECT ${SRC_M4} m0_bin.s)
 	set_target_properties(${PROJECT_NAME}_objects PROPERTIES COMPILE_FLAGS "${CFLAGS_M4}")
 	add_dependencies(${PROJECT_NAME}_objects ${PROJECT_NAME}_m0.bin)
-
-	# SPI flash version
 	add_executable(${PROJECT_NAME}.elf $<TARGET_OBJECTS:${PROJECT_NAME}_objects>)
 
 	target_link_libraries(
@@ -183,7 +182,11 @@ macro(DeclareTargets)
 	)
 
 	# DFU - using a differnet LD script to run directly from RAM
-	add_executable(${PROJECT_NAME}_dfu.elf $<TARGET_OBJECTS:${PROJECT_NAME}_objects>)
+	# Object files to be linked for DFU flash versions
+	add_library(${PROJECT_NAME}_dfu_objects OBJECT ${SRC_M4} m0_bin.s)
+	set_target_properties(${PROJECT_NAME}_dfu_objects PROPERTIES COMPILE_FLAGS "${CFLAGS_M4_DFU}")
+	add_dependencies(${PROJECT_NAME}_dfu_objects ${PROJECT_NAME}_m0.bin)
+	add_executable(${PROJECT_NAME}_dfu.elf $<TARGET_OBJECTS:${PROJECT_NAME}_dfu_objects>)
 
 	target_link_libraries(
 		${PROJECT_NAME}_dfu.elf

firmware/hackrf_usb/hackrf_usb.c

@@ -173,7 +173,9 @@ int main(void) {
 #endif
 	cpu_clock_init();
 
+#ifndef DFU_MODE
 	usb_set_descriptor_by_serial_number();
+#endif
 
 	usb_set_configuration_changed_cb(usb_configuration_changed);
 	usb_peripheral_reset();

firmware/hackrf_usb/usb_descriptor.c

@@ -253,8 +253,28 @@ uint8_t usb_descriptor_string_config_description[] = {
 	'r', 0x00,
 };
 
-
+#ifdef DFU_MODE
+uint8_t usb_descriptor_string_serial_number[] = {
+	30,						// bLength
+	USB_DESCRIPTOR_TYPE_STRING,		// bDescriptorType
+	'R', 0x00,
+	'u', 0x00,
+	'n', 0x00,
+	'n', 0x00,
+	'i', 0x00,
+	'n', 0x00,
+	'g', 0x00,
+	'F', 0x00,
+	'r', 0x00,
+	'o', 0x00,
+	'm', 0x00,
+	'R', 0x00,
+	'A', 0x00,
+	'M', 0x00,
+};
+#else
 uint8_t usb_descriptor_string_serial_number[USB_DESCRIPTOR_STRING_SERIAL_BUF_LEN];
+#endif
 
 uint8_t* usb_descriptor_strings[] = {
 	usb_descriptor_string_languages,

host/libhackrf/src/hackrf.c

@@ -101,6 +101,7 @@ typedef enum {
 
 #define TRANSFER_COUNT 4
 #define TRANSFER_BUFFER_SIZE 262144
+#define USB_MAX_SERIAL_LENGTH 32
 
 struct hackrf_device {
 	libusb_device_handle* usb_device;
@@ -437,10 +438,11 @@ hackrf_device_list_t* ADDCALL hackrf_device_list()
 						continue;
 					}
 					serial_number_length = libusb_get_string_descriptor_ascii(usb_device, serial_descriptor_index, (unsigned char*)serial_number, sizeof(serial_number));
-					if( serial_number_length == 32 ) {
+					if( serial_number_length >= USB_MAX_SERIAL_LENGTH )
-						serial_number[32] = 0;
+						serial_number_length = USB_MAX_SERIAL_LENGTH;
+
+					serial_number[serial_number_length] = 0;
 					list->serial_numbers[idx] = strdup(serial_number);
-					}
 					
 					libusb_close(usb_device);
 					usb_device = NULL;
@@ -505,18 +507,15 @@ libusb_device_handle* hackrf_open_usb(const char* const desired_serial_number)
 							continue;
 						}
 						serial_number_length = libusb_get_string_descriptor_ascii(usb_device, serial_descriptor_index, (unsigned char*)serial_number, sizeof(serial_number));
-						if( serial_number_length == 32 ) {
+						if( serial_number_length >= USB_MAX_SERIAL_LENGTH )
-							serial_number[32] = 0;
+							serial_number_length = USB_MAX_SERIAL_LENGTH;
-							if( strncmp(serial_number + 32-match_len, desired_serial_number, match_len) == 0 ) {
+						serial_number[serial_number_length] = 0;
+						if( strncmp(serial_number + serial_number_length-match_len, desired_serial_number, match_len) == 0 ) {
 							break;
 						} else {
 							libusb_close(usb_device);
 							usb_device = NULL;
 						}
-						} else {
-							libusb_close(usb_device);
-							usb_device = NULL;
-						}
 					}
 				} else {
 					libusb_open(devices[i], &usb_device);