diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5478126..bad1152 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,15 +1,13 @@
 name: CI
 
-on:
-  - push
-  - pull_request
+on: [push, pull_request]
 
 jobs:
   CI:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-20.04
     steps:
       - name: 'Check out code'
-        uses: actions/checkout@v4
+        uses: actions/checkout@v3
 
       - name: 'Install dependencies'
         run: |
@@ -30,7 +28,7 @@ jobs:
           make -C build
 
       - name: 'Upload binary'
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3
         with:
           name: pico-uart-bridge.uf2
           path: build/uart_bridge.uf2
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 881c3f6..e0c286d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,7 +7,7 @@ include(pico-sdk/pico_sdk_init.cmake)
 project(pico_uart_bridge)
 
 pico_sdk_init()
-
+  
 add_executable(uart_bridge uart-bridge.c usb-descriptors.c)
 
 target_include_directories(uart_bridge PUBLIC
diff --git a/README.md b/README.md
index 8c5d87d..c6a3967 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ Raspberry Pi Pico Pinout
 
 | Raspberry Pi Pico GPIO | Function |
 |:----------------------:|:--------:|
-| GPIO16 (Pin 21)        | UART0 TX |
-| GPIO17 (Pin 22)        | UART0 RX |
+| GPIO0 (Pin 1)          | UART0 TX |
+| GPIO1 (Pin 2)          | UART0 RX |
 | GPIO4 (Pin 6)          | UART1 TX |
 | GPIO5 (Pin 7)          | UART1 RX |
diff --git a/pico-sdk b/pico-sdk
index 6a7db34..2e6142b 160000
--- a/pico-sdk
+++ b/pico-sdk
@@ -1 +1 @@
-Subproject commit 6a7db34ff63345a7badec79ebea3aaef1712f374
+Subproject commit 2e6142b15b8a75c1227dd3edbe839193b2bf9041
diff --git a/tusb_config.h b/tusb_config.h
index 80eeb52..6fcb7b9 100644
--- a/tusb_config.h
+++ b/tusb_config.h
@@ -13,8 +13,8 @@
 #define CFG_TUSB_RHPORT0_MODE OPT_MODE_DEVICE
 
 #define CFG_TUD_CDC 2
-#define CFG_TUD_CDC_RX_BUFSIZE 1024
-#define CFG_TUD_CDC_TX_BUFSIZE 1024
+#define CFG_TUD_CDC_RX_BUFSIZE 256
+#define CFG_TUD_CDC_TX_BUFSIZE 256
 
 void usbd_serial_init(void);
 
diff --git a/uart-bridge.c b/uart-bridge.c
index c4e0805..7ee6a9c 100644
--- a/uart-bridge.c
+++ b/uart-bridge.c
@@ -17,7 +17,7 @@
 
 #define LED_PIN 25
 
-#define BUFFER_SIZE 2560
+#define BUFFER_SIZE 256
 
 #define DEF_BIT_RATE 115200
 #define DEF_STOP_BITS 1
@@ -26,8 +26,6 @@
 
 typedef struct {
 	uart_inst_t *const inst;
-	uint irq;
-	void *irq_fn;
 	uint8_t tx_pin;
 	uint8_t rx_pin;
 } uart_id_t;
@@ -44,20 +42,13 @@ typedef struct {
 	mutex_t usb_mtx;
 } uart_data_t;
 
-void uart0_irq_fn(void);
-void uart1_irq_fn(void);
-
 const uart_id_t UART_ID[CFG_TUD_CDC] = {
 	{
 		.inst = uart0,
-		.irq = UART0_IRQ,
-		.irq_fn = &uart0_irq_fn,
-		.tx_pin = 16,
-		.rx_pin = 17,
+		.tx_pin = 0,
+		.rx_pin = 1,
 	}, {
 		.inst = uart1,
-		.irq = UART1_IRQ,
-		.irq_fn = &uart1_irq_fn,
 		.tx_pin = 4,
 		.rx_pin = 5,
 	}
@@ -128,13 +119,14 @@ void update_uart_cfg(uint8_t itf)
 	mutex_exit(&ud->lc_mtx);
 }
 
-void usb_read_bytes(uint8_t itf)
-{
-	uart_data_t *ud = &UART_DATA[itf];
+void usb_read_bytes(uint8_t itf) {
 	uint32_t len = tud_cdc_n_available(itf);
 
-	if (len &&
-	    mutex_try_enter(&ud->usb_mtx, NULL)) {
+	if (len) {
+		uart_data_t *ud = &UART_DATA[itf];
+
+		mutex_enter_blocking(&ud->usb_mtx);
+
 		len = MIN(len, BUFFER_SIZE - ud->usb_pos);
 		if (len) {
 			uint32_t count;
@@ -147,17 +139,17 @@ void usb_read_bytes(uint8_t itf)
 	}
 }
 
-void usb_write_bytes(uint8_t itf)
-{
+void usb_write_bytes(uint8_t itf) {
 	uart_data_t *ud = &UART_DATA[itf];
 
-	if (ud->uart_pos &&
-	    mutex_try_enter(&ud->uart_mtx, NULL)) {
+	if (ud->uart_pos) {
 		uint32_t count;
 
+		mutex_enter_blocking(&ud->uart_mtx);
+
 		count = tud_cdc_n_write(itf, ud->uart_buffer, ud->uart_pos);
 		if (count < ud->uart_pos)
-			memmove(ud->uart_buffer, &ud->uart_buffer[count],
+			memcpy(ud->uart_buffer, &ud->uart_buffer[count],
 			       ud->uart_pos - count);
 		ud->uart_pos -= count;
 
@@ -189,7 +181,7 @@ void core1_entry(void)
 		int con = 0;
 
 		tud_task();
-
+	
 		for (itf = 0; itf < CFG_TUD_CDC; itf++) {
 			if (tud_cdc_n_connected(itf)) {
 				con = 1;
@@ -201,16 +193,16 @@ void core1_entry(void)
 	}
 }
 
-static inline void uart_read_bytes(uint8_t itf)
-{
-	uart_data_t *ud = &UART_DATA[itf];
+void uart_read_bytes(uint8_t itf) {
 	const uart_id_t *ui = &UART_ID[itf];
 
 	if (uart_is_readable(ui->inst)) {
+		uart_data_t *ud = &UART_DATA[itf];
+
 		mutex_enter_blocking(&ud->uart_mtx);
 
 		while (uart_is_readable(ui->inst) &&
-		       (ud->uart_pos < BUFFER_SIZE)) {
+			ud->uart_pos < BUFFER_SIZE) {
 			ud->uart_buffer[ud->uart_pos] = uart_getc(ui->inst);
 			ud->uart_pos++;
 		}
@@ -219,42 +211,22 @@ static inline void uart_read_bytes(uint8_t itf)
 	}
 }
 
-void uart0_irq_fn(void)
-{
-	uart_read_bytes(0);
-}
-
-void uart1_irq_fn(void)
-{
-	uart_read_bytes(1);
-}
-
-void uart_write_bytes(uint8_t itf)
-{
+void uart_write_bytes(uint8_t itf) {
 	uart_data_t *ud = &UART_DATA[itf];
 
-	if (ud->usb_pos &&
-	    mutex_try_enter(&ud->usb_mtx, NULL)) {
+	if (ud->usb_pos) {
 		const uart_id_t *ui = &UART_ID[itf];
-		uint32_t count = 0;
 
-		while (uart_is_writable(ui->inst) &&
-		       count < ud->usb_pos) {
-			uart_putc_raw(ui->inst, ud->usb_buffer[count]);
-			count++;
-		}
+		mutex_enter_blocking(&ud->usb_mtx);
 
-		if (count < ud->usb_pos)
-			memmove(ud->usb_buffer, &ud->usb_buffer[count],
-			       ud->usb_pos - count);
-		ud->usb_pos -= count;
+		uart_write_blocking(ui->inst, ud->usb_buffer, ud->usb_pos);
+		ud->usb_pos = 0;
 
 		mutex_exit(&ud->usb_mtx);
 	}
 }
 
-void init_uart_data(uint8_t itf)
-{
+void init_uart_data(uint8_t itf) {
 	const uart_id_t *ui = &UART_ID[itf];
 	uart_data_t *ud = &UART_DATA[itf];
 
@@ -289,18 +261,14 @@ void init_uart_data(uint8_t itf)
 	uart_set_format(ui->inst, databits_usb2uart(ud->usb_lc.data_bits),
 			stopbits_usb2uart(ud->usb_lc.stop_bits),
 			parity_usb2uart(ud->usb_lc.parity));
-	uart_set_fifo_enabled(ui->inst, false);
-
-	/* UART RX Interrupt */
-	irq_set_exclusive_handler(ui->irq, ui->irq_fn);
-	irq_set_enabled(ui->irq, true);
-	uart_set_irq_enables(ui->inst, true, false);
 }
 
 int main(void)
 {
 	int itf;
 
+	set_sys_clock_khz(250000, false);
+
 	usbd_serial_init();
 
 	for (itf = 0; itf < CFG_TUD_CDC; itf++)
@@ -314,6 +282,7 @@ int main(void)
 	while (1) {
 		for (itf = 0; itf < CFG_TUD_CDC; itf++) {
 			update_uart_cfg(itf);
+			uart_read_bytes(itf);
 			uart_write_bytes(itf);
 		}
 	}
diff --git a/usb-descriptors.c b/usb-descriptors.c
index 738f9d0..1ccd5de 100644
--- a/usb-descriptors.c
+++ b/usb-descriptors.c
@@ -18,21 +18,18 @@
 #define USBD_PID 0x000A /* Raspberry Pi Pico SDK CDC */
 
 #define USBD_DESC_LEN (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN * CFG_TUD_CDC)
-#define USBD_MAX_POWER_MA 500
+#define USBD_MAX_POWER_MA 250
 
 #define USBD_ITF_CDC_0 0
 #define USBD_ITF_CDC_1 2
 #define USBD_ITF_MAX 4
 
 #define USBD_CDC_0_EP_CMD 0x81
-#define USBD_CDC_1_EP_CMD 0x83
-
-#define USBD_CDC_0_EP_OUT 0x01
-#define USBD_CDC_1_EP_OUT 0x03
-
+#define USBD_CDC_1_EP_CMD 0x84
+#define USBD_CDC_0_EP_OUT 0x02
+#define USBD_CDC_1_EP_OUT 0x05
 #define USBD_CDC_0_EP_IN 0x82
-#define USBD_CDC_1_EP_IN 0x84
-
+#define USBD_CDC_1_EP_IN 0x85
 #define USBD_CDC_CMD_MAX_SIZE 8
 #define USBD_CDC_IN_OUT_MAX_SIZE 64