diff --git a/CH5xx_ble_firmware_library/StdPeriphDriver/CH58x_i2c.c b/CH5xx_ble_firmware_library/StdPeriphDriver/CH58x_i2c.c
index 48d3355..f9aaf8c 100644
--- a/CH5xx_ble_firmware_library/StdPeriphDriver/CH58x_i2c.c
+++ b/CH5xx_ble_firmware_library/StdPeriphDriver/CH58x_i2c.c
@@ -81,7 +81,7 @@ void I2C_Init(I2C_ModeTypeDef I2C_Mode, UINT32 I2C_ClockSpeed, I2C_DutyTypeDef I
     R16_I2C_CTRL1 &= ~(RB_I2C_SMBUS | RB_I2C_SMBTYPE | RB_I2C_ACK);
     R16_I2C_CTRL1 |= I2C_Mode | I2C_Ack;
 
-    R16_I2C_OADDR1 &= ~0xFFFF;
+    R16_I2C_OADDR1 &= ~0xFFFFU;
     R16_I2C_OADDR1 |= I2C_AckAddr | I2C_OwnAddress1;
 }
 
diff --git a/Makefile b/Makefile
index a4e6916..2601737 100644
--- a/Makefile
+++ b/Makefile
@@ -56,7 +56,6 @@ CH5xx_ble_firmware_library/StdPeriphDriver/CH58x_usb2dev.c \
 CH5xx_ble_firmware_library/StdPeriphDriver/CH58x_spi1.c \
 CH5xx_ble_firmware_library/RVMSIS/core_riscv.c \
 src/main.c \
-src/debug.c \
 src/leddrv.c \
 src/button.c \
 src/bmlist.c \
@@ -74,7 +73,6 @@ src/data.c \
 src/usb/utils.c \
 src/usb/setup.c \
 src/usb/ctrl.c \
-src/usb/debug.c \
 src/usb/dev.c \
 src/usb/composite/hiddev.c \
 src/usb/composite/cdc-serial.c \
@@ -84,6 +82,11 @@ src/animation.c \
 src/font.c \
 src/power.c \
 
+ifdef DEBUG
+C_SOURCES += \
+src/debug.c \
+src/usb/debug.c
+endif
 
 # ASM sources
 ASM_SOURCES =  \
diff --git a/src/ble/common.h b/src/ble/common.h
index 6c03121..e5354ad 100644
--- a/src/ble/common.h
+++ b/src/ble/common.h
@@ -10,7 +10,7 @@
 #include <stddef.h>
 
 typedef struct {
-	uint8_t *bytes;
+	const uint8_t *bytes;
 	int size;
 } byte_t;
 
diff --git a/src/bmlist.c b/src/bmlist.c
index 420386e..14d8d25 100644
--- a/src/bmlist.c
+++ b/src/bmlist.c
@@ -1,7 +1,7 @@
 #include "bmlist.h"
 #include <memory.h>
 
-volatile static bm_t *current, *head, *tail;
+static bm_t *current, *head, *tail;
 
 static void bm_add(bm_t *new, bm_t *prev, bm_t *next)
 {
@@ -63,13 +63,14 @@ static void list_del(bm_t *prev, bm_t *next)
 
 bm_t *bmlist_drop(bm_t *bm)
 {
+	bm_t *next = bm->next;
 	list_del(bm->prev, bm->next);
 	if (bm == head)
 		head = bm->next;
 	if (bm == tail)
 		tail = bm->prev;
 	free(bm);
-	return bm->next;
+	return next;
 }
 
 bm_t *bm_new(uint16_t width)
diff --git a/src/config.c b/src/config.c
index ac91b85..af47422 100644
--- a/src/config.c
+++ b/src/config.c
@@ -4,7 +4,6 @@
  */
 #include "config.h"
 #include "resource.h"
-#include "res/foss-asia-2.xbm"
 #include "debug.h"
 #include "util/crc.h"
 
diff --git a/src/data.c b/src/data.c
index 1261c90..e8e1f92 100644
--- a/src/data.c
+++ b/src/data.c
@@ -7,11 +7,16 @@
 #include "data.h"
 #include "leddrv.h"
 
-uint32_t bigendian16_sum(uint16_t *s, int len)
+uint32_t bigendian16_sum(const uint8_t *s, int len)
 {
 	uint32_t sum = 0;
 	while (len-- > 0) {
-		sum += bswap16(s[len]);
+		// Read the big-endian bytes for this uint16_t
+		uint8_t high = s[len * 2];      // MSB (most significant byte)
+		uint8_t low = s[len * 2 + 1];   // LSB (least significant byte)
+		// Reconstruct the uint16_t value (big-endian to little-endian equivalent)
+		uint16_t val = (high << 8) | low;
+  sum += val;
 	}
 	return sum;
 }
@@ -42,7 +47,7 @@ uint16_t data_flash2newmem(uint8_t **chunk, uint32_t n)
 		return 0;
 
 	uint16_t offs = LEGACY_HEADER_SIZE
-		+ bigendian16_sum(header.sizes, n) * LED_ROWS;
+		+ bigendian16_sum((const uint8_t*)header.sizes, n) * LED_ROWS;
 
 	*chunk = malloc(size);
 	EEPROM_READ(offs, *chunk, size);
diff --git a/src/data.h b/src/data.h
index ef4050c..b57f364 100644
--- a/src/data.h
+++ b/src/data.h
@@ -42,7 +42,7 @@ enum ANIMATION_MODES {
 static inline uint16_t bswap16(uint16_t i) {
 	return (i >> 8) | (i << 8);
 }
-uint32_t bigendian16_sum(uint16_t *s, int len);
+uint32_t bigendian16_sum(const uint8_t *s, int len);
 
 uint32_t data_flatSave(uint8_t *data, uint32_t len);
 uint16_t data_flash2newmem(uint8_t **chunk, uint32_t n);
diff --git a/src/legacyctrl.c b/src/legacyctrl.c
index 582d6e4..4bb22c8 100644
--- a/src/legacyctrl.c
+++ b/src/legacyctrl.c
@@ -50,7 +50,7 @@ int legacy_ble_rx(uint8_t *val, uint16_t len)
 
 	if (c == 1) {
 		data_legacy_t *d = (data_legacy_t *)data;
-		n = bigendian16_sum(d->sizes, 8);
+		n = bigendian16_sum((uint8_t*)d->sizes, 8);
 		data_len = LEGACY_HEADER_SIZE + LED_ROWS * n;
 		PRINT("Data len: %d\n", data_len);
 		data = realloc(data, data_len);
@@ -96,7 +96,7 @@ int legacy_usb_rx(uint8_t *buf, uint16_t len)
 
 	if (!data_len) {
 		data_legacy_t *d = (data_legacy_t *)data;
-		uint16_t n = bigendian16_sum(d->sizes, 8);
+		uint16_t n = bigendian16_sum((uint8_t*)d->sizes, 8);
 		data_len = LEGACY_HEADER_SIZE + LED_ROWS * n;
 		data = realloc(data, data_len);
 	}
diff --git a/src/main.c b/src/main.c
index 10a62e0..377e14e 100644
--- a/src/main.c
+++ b/src/main.c
@@ -49,7 +49,7 @@ enum MODES {
 
 static tmosTaskID common_taskid = INVALID_TASK_ID ;
 
-volatile uint16_t fb[LED_COLS] = {0};
+uint16_t fb[LED_COLS] = {0};
 volatile int mode, is_play_sequentially = 1;
 
 __HIGH_CODE
@@ -435,7 +435,7 @@ int main()
 	disp_charging();
 	cfg_init();
 	xbm_t spl = {
-		.bits = &(badge_cfg.splash_bm_bits),
+		.bits = badge_cfg.splash_bm_bits,
 		.w = badge_cfg.splash_bm_w,
 		.h = badge_cfg.splash_bm_h,
 		.fh = badge_cfg.splash_bm_fh,
diff --git a/src/ngctrl.c b/src/ngctrl.c
index 5e78cbb..f2226fd 100644
--- a/src/ngctrl.c
+++ b/src/ngctrl.c
@@ -125,7 +125,7 @@ uint8_t load_fallback_cfg(uint8_t *val, uint16_t len)
 {
 	PRINT(__func__);
 	PRINT("\n");
-	cfg_fallback(&badge_cfg);
+	cfg_fallback();
 	return 0;
 }
 
diff --git a/src/power.c b/src/power.c
index da6ec0f..1e6b4f9 100644
--- a/src/power.c
+++ b/src/power.c
@@ -27,8 +27,7 @@ void power_init()
 	GPIOA_ModeCfg(GPIO_Pin_5, GPIO_ModeIN_Floating);
 	ADC_ExtSingleChSampInit(SampleFreq_3_2, ADC_PGA_0);
 
-	int16_t adc_calib = ADC_DataCalib_Rough();
-	PRINT("RoughCalib_Value = %d \n", adc_calib);
+	PRINT("RoughCalib_Value = %d \n", ADC_DataCalib_Rough());
 
 	ADC_ChannelCfg(1);
 }
@@ -38,7 +37,6 @@ int batt_raw()
 	int ret = 0;
 
 	PRINT("ADC reading: \n");
-	uint16_t buf[20];
 	for(int i = 0; i < 20; i++) {
 		uint16_t adc = ADC_ExcutSingleConver();
 		ret += adc;
diff --git a/src/res/foss-asia-2.xbm b/src/res/foss-asia-2.xbm
index 5a75f5d..cf9623a 100644
--- a/src/res/foss-asia-2.xbm
+++ b/src/res/foss-asia-2.xbm
@@ -1,6 +1,6 @@
 #define foss_asia_2_width 44
 #define foss_asia_2_height 22
-static unsigned char foss_asia_2_bits[] = {
+unsigned const char foss_asia_2_bits[] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfc, 0xf9, 0x8f, 0xff, 0xfc, 0x07,
    0xfe, 0xfd, 0xdf, 0xff, 0xfe, 0x07, 0x06, 0x0c, 0xd8, 0x00, 0x06, 0x00,
    0xff, 0x0d, 0xd8, 0x7f, 0xfe, 0x03, 0xff, 0x0d, 0x98, 0xff, 0xfc, 0x07,
diff --git a/src/usb/composite/cdc-serial.c b/src/usb/composite/cdc-serial.c
index 99f0c40..1295e61 100644
--- a/src/usb/composite/cdc-serial.c
+++ b/src/usb/composite/cdc-serial.c
@@ -13,8 +13,6 @@
 #define USB_DESCTYPE_CS_INTERFACE 0x24
 
 static __attribute__((aligned(4))) uint8_t noti_ep_buf[64 + 64]; 
-static uint8_t *const noti_ep_out = noti_ep_buf;
-static uint8_t *const noti_ep_in = noti_ep_buf + 64;
 
 static __attribute__((aligned(4))) uint8_t data_ep_buf[64 + 64]; 
 static uint8_t *const data_ep_out = data_ep_buf;
diff --git a/src/usb/ctrl.c b/src/usb/ctrl.c
index 30aa7dd..b506690 100644
--- a/src/usb/ctrl.c
+++ b/src/usb/ctrl.c
@@ -19,7 +19,7 @@ void usb_set_address(uint8_t ad)
 	address = ad;
 }
 
-void ctrl_start_load_block(void *buf, uint16_t len)
+void ctrl_start_load_block(const void *buf, uint16_t len)
 {
 	usb_start_load_block(ep0buf, buf, len, 1);
 }
@@ -53,7 +53,9 @@ static void ep_handler()
 	switch(token) {
 
 	case UIS_TOKEN_SETUP:
-		print_setuppk(req);
+		#ifdef DEBUG
+		print_setuppk(request);
+		#endif
 
 		if (recip == USB_REQ_RECIP_DEVICE) {
 			handle_devreq(request);
@@ -128,12 +130,16 @@ __HIGH_CODE
 void USB_IRQHandler(void) {
 	uint8_t intflag = R8_USB_INT_FG;
 	clear_handshake_sent_flag();
+	#ifdef DEBUG
 	PRINT("\nusb: new interrupt\n");
 	print_intflag_reg();
+	#endif
 
 	if (intflag & RB_UIF_TRANSFER) {
+		#ifdef DEBUG
 		PRINT("usb: RX Length reg: %d\n", R8_USB_RX_LEN);
 		print_status_reg();
+		#endif
 
 		route_enpoints();
 	}
diff --git a/src/usb/dev.c b/src/usb/dev.c
index 569dd25..cfca8fd 100644
--- a/src/usb/dev.c
+++ b/src/usb/dev.c
@@ -28,7 +28,7 @@ USB_DEV_DESCR dev_desc = {
 };
 
 /* String Descriptor Zero, Specifying Languages Supported by the Device */
-static uint8_t lang_desc[] = {
+static uint16_t lang_desc[] = {
 	0x04,       /* bLength */
 	0x03,       /* bDescriptorType */
 	0x09, 0x04  /* wLANGID - en-US */
@@ -91,7 +91,7 @@ static void desc_config(USB_SETUP_REQ *request)
 
 static void desc_string(USB_SETUP_REQ *request)
 {
-	uint8_t *string_index[32] = {
+	uint16_t *string_index[32] = {
 		lang_desc,
 		vendor_info,
 		product_info,
diff --git a/src/usb/usb.h b/src/usb/usb.h
index f1d41f9..f89966c 100644
--- a/src/usb/usb.h
+++ b/src/usb/usb.h
@@ -5,11 +5,11 @@
 
 void cdc_fill_IN(uint8_t *buf, uint8_t len);
 int cdc_tx_poll(uint8_t *buf, int len, uint16_t timeout_ms);
-void cdc_onWrite(void (*cb)(uint8_t *buf, uint16_t len));
+void cdc_onWrite(int (*cb)(uint8_t *buf, uint16_t len));
 
 void hiddev_fill_IN(uint8_t *buf, uint8_t len);
 int hiddev_tx_poll(uint8_t *buf, int len, uint16_t timeout_ms);
-void hiddev_onWrite(void (*cb)(uint8_t *buf, uint16_t len));
+void hiddev_onWrite(int (*cb)(uint8_t *buf, uint16_t len));
 
 void usb_start();
 
diff --git a/src/usb/utils.c b/src/usb/utils.c
index 5c6a83e..9ca2cbc 100644
--- a/src/usb/utils.c
+++ b/src/usb/utils.c
@@ -35,9 +35,8 @@ static void __handshake(uint8_t ep_num, int dir, int type, int tog, uint8_t len)
 	if (ep_num > 7)
 		return;
 
-	char *type_mean[] = { "ACK", "NO_RESP", "NAK", "STALL"};
 	PRINT("Loaded %d byte, DATA%d with an %s to EP%dIN.\n",
-			len, tog != 0, type_mean[type], ep_num);
+			len, tog != 0, ((char *[]){ "ACK", "NO_RESP", "NAK", "STALL"})[type], ep_num);
 
 	uint8_t ctrl = type << (dir ? 0 : 2);
 	ctrl |= (tog) ? RB_UEP_T_TOG : RB_UEP_R_TOG;
@@ -69,11 +68,11 @@ int handshake_sent()
 	return res_sent;
 }
 
-static uint8_t *p_buf;
+static const uint8_t *p_buf;
 static uint16_t remain_len, req_len, _tog;
 
 static uint16_t 
-load_chunk(void *ep_buf, void *block, uint16_t block_len, uint16_t req_len, 
+load_chunk(void *ep_buf, const void *block, uint16_t block_len, uint16_t req_len, 
 				int tog)
 {
 	_TRACE();
@@ -119,7 +118,7 @@ int usb_load_next_chunk()
 }
 
 uint16_t
-usb_start_load_block(void *ep_IN_buf, void *buf, uint16_t len, int tog)
+usb_start_load_block(void *ep_IN_buf, const void *buf, uint16_t len, int tog)
 {
 	_TRACE();
 	req_len = len;
diff --git a/src/usb/utils.h b/src/usb/utils.h
index 595a8b7..921d354 100644
--- a/src/usb/utils.h
+++ b/src/usb/utils.h
@@ -16,8 +16,8 @@ int if_cb_register(uint8_t if_num, void (*cb)(USB_SETUP_REQ *request));
 void dma_register(uint8_t endpoint_number, void *buf_addr);
 
 uint16_t
-usb_start_load_block(void *ep_IN_buf, void *buf, uint16_t len, int tog);
-void ctrl_start_load_block(void *buf, uint16_t len);
+usb_start_load_block(void *ep_IN_buf, const void *buf, uint16_t len, int tog);
+void ctrl_start_load_block(const void *buf, uint16_t len);
 int usb_load_next_chunk();
 void usb_flush();
 
diff --git a/src/xbm.h b/src/xbm.h
index 7bf9530..652cb64 100644
--- a/src/xbm.h
+++ b/src/xbm.h
@@ -7,7 +7,7 @@
 #define ALIGN_8BIT(x) (ALIGN_1BYTE(x) * 8)
 
 typedef struct {
-	uint8_t *bits;
+	const uint8_t *bits;
 	int     w; // Width
 	int     h; // Height
 	int     fh; // Frame height