diff --git a/examples/host/cdc_msc_hid/src/cdc_app.c b/examples/host/cdc_msc_hid/src/cdc_app.c
index a1b26e49c..81052047c 100644
--- a/examples/host/cdc_msc_hid/src/cdc_app.c
+++ b/examples/host/cdc_msc_hid/src/cdc_app.c
@@ -27,20 +27,11 @@
 #include "tusb.h"
 #include "bsp/board_api.h"
 
-//--------------------------------------------------------------------+
-// MACRO TYPEDEF CONSTANT ENUM DECLARATION
-//--------------------------------------------------------------------+
-
-
-//------------- IMPLEMENTATION -------------//
-
-size_t get_console_inputs(uint8_t* buf, size_t bufsize)
-{
+size_t get_console_inputs(uint8_t* buf, size_t bufsize) {
   size_t count = 0;
-  while (count < bufsize)
-  {
+  while (count < bufsize) {
     int ch = board_getchar();
-    if ( ch <= 0 ) break;
+    if (ch <= 0) break;
 
     buf[count] = (uint8_t) ch;
     count++;
@@ -49,22 +40,18 @@ size_t get_console_inputs(uint8_t* buf, size_t bufsize)
   return count;
 }
 
-void cdc_app_task(void)
-{
-  uint8_t buf[64+1]; // +1 for extra null character
-  uint32_t const bufsize = sizeof(buf)-1;
+void cdc_app_task(void) {
+  uint8_t buf[64 + 1]; // +1 for extra null character
+  uint32_t const bufsize = sizeof(buf) - 1;
 
   uint32_t count = get_console_inputs(buf, bufsize);
   buf[count] = 0;
 
   // loop over all mounted interfaces
-  for(uint8_t idx=0; idx<CFG_TUH_CDC; idx++)
-  {
-    if ( tuh_cdc_mounted(idx) )
-    {
+  for (uint8_t idx = 0; idx < CFG_TUH_CDC; idx++) {
+    if (tuh_cdc_mounted(idx)) {
       // console --> cdc interfaces
-      if (count)
-      {
+      if (count) {
         tuh_cdc_write(idx, buf, count);
         tuh_cdc_write_flush(idx);
       }
@@ -72,11 +59,14 @@ void cdc_app_task(void)
   }
 }
 
+//--------------------------------------------------------------------+
+// TinyUSB callbacks
+//--------------------------------------------------------------------+
+
 // Invoked when received new data
-void tuh_cdc_rx_cb(uint8_t idx)
-{
-  uint8_t buf[64+1]; // +1 for extra null character
-  uint32_t const bufsize = sizeof(buf)-1;
+void tuh_cdc_rx_cb(uint8_t idx) {
+  uint8_t buf[64 + 1]; // +1 for extra null character
+  uint32_t const bufsize = sizeof(buf) - 1;
 
   // forward cdc interfaces -> console
   uint32_t count = tuh_cdc_read(idx, buf, bufsize);
@@ -85,29 +75,31 @@ void tuh_cdc_rx_cb(uint8_t idx)
   printf((char*) buf);
 }
 
-void tuh_cdc_mount_cb(uint8_t idx)
-{
-  tuh_itf_info_t itf_info = { 0 };
+// Invoked when a device with CDC interface is mounted
+// idx is index of cdc interface in the internal pool.
+void tuh_cdc_mount_cb(uint8_t idx) {
+  tuh_itf_info_t itf_info = {0};
   tuh_cdc_itf_get_info(idx, &itf_info);
 
-  printf("CDC Interface is mounted: address = %u, itf_num = %u\r\n", itf_info.daddr, itf_info.desc.bInterfaceNumber);
+  printf("CDC Interface is mounted: address = %u, itf_num = %u\r\n", itf_info.daddr,
+         itf_info.desc.bInterfaceNumber);
 
 #ifdef CFG_TUH_CDC_LINE_CODING_ON_ENUM
   // CFG_TUH_CDC_LINE_CODING_ON_ENUM must be defined for line coding is set by tinyusb in enumeration
   // otherwise you need to call tuh_cdc_set_line_coding() first
-  cdc_line_coding_t line_coding = { 0 };
-  if ( tuh_cdc_get_local_line_coding(idx, &line_coding) )
-  {
+  cdc_line_coding_t line_coding = {0};
+  if (tuh_cdc_get_local_line_coding(idx, &line_coding)) {
     printf("  Baudrate: %lu, Stop Bits : %u\r\n", line_coding.bit_rate, line_coding.stop_bits);
-    printf("  Parity  : %u, Data Width: %u\r\n", line_coding.parity  , line_coding.data_bits);
+    printf("  Parity  : %u, Data Width: %u\r\n", line_coding.parity, line_coding.data_bits);
   }
 #endif
 }
 
-void tuh_cdc_umount_cb(uint8_t idx)
-{
-  tuh_itf_info_t itf_info = { 0 };
+// Invoked when a device with CDC interface is unmounted
+void tuh_cdc_umount_cb(uint8_t idx) {
+  tuh_itf_info_t itf_info = {0};
   tuh_cdc_itf_get_info(idx, &itf_info);
 
-  printf("CDC Interface is unmounted: address = %u, itf_num = %u\r\n", itf_info.daddr, itf_info.desc.bInterfaceNumber);
+  printf("CDC Interface is unmounted: address = %u, itf_num = %u\r\n", itf_info.daddr,
+         itf_info.desc.bInterfaceNumber);
 }
diff --git a/src/class/cdc/cdc_host.c b/src/class/cdc/cdc_host.c
index bfaa64a77..37fa30982 100644
--- a/src/class/cdc/cdc_host.c
+++ b/src/class/cdc/cdc_host.c
@@ -1327,48 +1327,88 @@ static void ch34x_control_complete(tuh_xfer_t* xfer) {
   process_internal_control_complete(p_cdc, xfer);
 }
 
-//static bool ch34x_set_data_format(cdch_interface_t* p_cdc, uint8_t stop_bits, uint8_t parity, uint8_t data_bits,
-//                                tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
-//  uint8_t const lcr = ch34x_get_lcr(stop_bits, parity, data_bits);
-//  p_cdc->requested_line_coding.stop_bits = stop_bits;
-//  p_cdc->requested_line_coding.parity = parity;
-//  p_cdc->requested_line_coding.data_bits = data_bits;
-//
-//  TU_ASSERT (ch34x_control_out(p_cdc, CH34X_REQ_WRITE_REG, CH32X_REG16_LCR2_LCR, lcr,
-//                                complete_cb ? ch34x_control_complete : NULL, user_data));
-//  return false;
-//}
-
-static bool ch34x_set_baudrate(cdch_interface_t* p_cdc, uint32_t baudrate,
-                               tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
-  uint16_t const div_ps = ch34x_get_divisor_prescaler(baudrate);
-  TU_VERIFY(div_ps != 0);
-
-  p_cdc->requested_line_coding.bit_rate = baudrate;
-  p_cdc->user_control_cb = complete_cb;
-  TU_ASSERT(ch34x_write_reg(p_cdc, CH34X_REG16_DIVISOR_PRESCALER, div_ps,
-                            complete_cb ? ch34x_control_complete : NULL, user_data));
+static bool ch34x_set_data_format(cdch_interface_t* p_cdc, uint8_t stop_bits, uint8_t parity, uint8_t data_bits,
+                                tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
+  p_cdc->requested_line_coding.stop_bits = stop_bits;
+  p_cdc->requested_line_coding.parity = parity;
+  p_cdc->requested_line_coding.data_bits = data_bits;
 
+  uint8_t const lcr = ch34x_get_lcr(stop_bits, parity, data_bits);
+  TU_ASSERT (ch34x_control_out(p_cdc, CH34X_REQ_WRITE_REG, CH32X_REG16_LCR2_LCR, lcr,
+                               complete_cb ? ch34x_control_complete : NULL, user_data));
   return true;
 }
 
-//static void ch34x_set_line_coding_stage1(tuh_xfer_t* xfer) {
-//
-//}
+static bool ch34x_write_reg_baudrate(cdch_interface_t* p_cdc, uint32_t baudrate,
+                                     tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
+  uint16_t const div_ps = ch34x_get_divisor_prescaler(baudrate);
+  TU_VERIFY(div_ps != 0);
+  TU_ASSERT(ch34x_write_reg(p_cdc, CH34X_REG16_DIVISOR_PRESCALER, div_ps,
+                            complete_cb, user_data));
+  return true;
+}
 
+static bool ch34x_set_baudrate(cdch_interface_t* p_cdc, uint32_t baudrate,
+                               tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
+  p_cdc->requested_line_coding.bit_rate = baudrate;
+  p_cdc->user_control_cb = complete_cb;
+  TU_ASSERT(ch34x_write_reg_baudrate(p_cdc, baudrate,
+                                     complete_cb ? ch34x_control_complete : NULL, user_data));
+  return true;
+}
+
+static void ch34x_set_line_coding_stage1_complete(tuh_xfer_t* xfer) {
+  uint8_t const itf_num = 0;
+  uint8_t const idx = tuh_cdc_itf_get_index(xfer->daddr, itf_num);
+  cdch_interface_t* p_cdc = get_itf(idx);
+  TU_ASSERT(p_cdc, );
+
+  if (xfer->result == XFER_RESULT_SUCCESS) {
+    // stage 1 success, continue to stage 2
+    p_cdc->line_coding.bit_rate = p_cdc->requested_line_coding.bit_rate;
+    TU_ASSERT(ch34x_set_data_format(p_cdc, p_cdc->requested_line_coding.stop_bits, p_cdc->requested_line_coding.parity,
+                                    p_cdc->requested_line_coding.data_bits, ch34x_control_complete, xfer->user_data), );
+  } else {
+    // stage 1 failed, notify user
+    xfer->complete_cb = p_cdc->user_control_cb;
+    if (xfer->complete_cb) {
+      xfer->complete_cb(xfer);
+    }
+  }
+}
+
+// 2 stages: set baudrate (stage1) + set data format (stage2)
 static bool ch34x_set_line_coding(cdch_interface_t* p_cdc, cdc_line_coding_t const* line_coding,
                                   tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
-//  p_cdc->baudrate_requested = line_coding->bit_rate;
-//  p_cdc->user_control_cb = complete_cb;
-//  uint8_t factor, divisor, lcr;
-//  TU_ASSERT (ch34x_get_factor_divisor(line_coding->bit_rate, &factor, &divisor));
-//  TU_ASSERT (ch34x_get_lcr(line_coding, &lcr));
-//  TU_ASSERT (ch34x_control_out(p_cdc, CH34X_REQ_SERIAL_INIT, (uint16_t) (lcr << 8 | 0x9c), (uint16_t) (factor << 8 | 0x80 | divisor),
-//                               complete_cb ? ch34x_control_complete : NULL, user_data));
-  (void) p_cdc;
-  (void) line_coding;
-  (void) complete_cb;
-  (void) user_data;
+  p_cdc->requested_line_coding = *line_coding;
+  p_cdc->user_control_cb = complete_cb;
+
+  if (complete_cb) {
+    // stage 1 set baudrate
+    TU_ASSERT(ch34x_write_reg_baudrate(p_cdc, line_coding->bit_rate,
+                                       ch34x_set_line_coding_stage1_complete, user_data));
+  } else {
+    // sync call
+    xfer_result_t result;
+
+    // stage 1 set baudrate
+    TU_ASSERT(ch34x_write_reg_baudrate(p_cdc, line_coding->bit_rate, NULL, (uintptr_t) &result));
+    TU_VERIFY(result == XFER_RESULT_SUCCESS);
+    p_cdc->line_coding.bit_rate = line_coding->bit_rate;
+
+    // stage 2 set data format
+    TU_ASSERT(ch34x_set_data_format(p_cdc, line_coding->stop_bits, line_coding->parity, line_coding->data_bits,
+                                    NULL, (uintptr_t) &result));
+    TU_VERIFY(result == XFER_RESULT_SUCCESS);
+    p_cdc->line_coding.stop_bits = line_coding->stop_bits;
+    p_cdc->line_coding.parity = line_coding->parity;
+    p_cdc->line_coding.data_bits = line_coding->data_bits;
+
+    // update transfer result, user_data is expected to point to xfer_result_t
+    if (user_data) {
+      user_data = result;
+    }
+  }
 
   return true;
 }
diff --git a/src/class/cdc/serial/ch34x.h b/src/class/cdc/serial/ch34x.h
index 3f78a3007..5def8d212 100644
--- a/src/class/cdc/serial/ch34x.h
+++ b/src/class/cdc/serial/ch34x.h
@@ -63,7 +63,8 @@
 #define CH341_REG_0x2C         0x2C // undocumented register
 #define CH341_REG_0x27         0x27 // hardware flow control (cts/rts)
 
-#define CH34X_REG16_DIVISOR_PRESCALER TU_U16(CH34X_REG_DIVISOR, CH34X_REG_PRESCALER)
+#define CH34X_REG16_DIVISOR_PRESCALER  TU_U16(CH34X_REG_DIVISOR, CH34X_REG_PRESCALER)
+#define CH32X_REG16_LCR2_LCR           TU_U16(CH34X_REG_LCR2, CH34X_REG_LCR)
 
 // modem control bits
 #define CH34X_BIT_RTS ( 1 << 6 )