diff --git a/CMakeLists.txt b/CMakeLists.txt
index 252bf4e..13cc1b8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,6 +12,7 @@ add_executable(picoprobe
         src/usb_descriptors.c
         src/probe.c
         src/cdc_uart.c
+        src/cdc_sump.c
         src/get_serial.c
 )
 
diff --git a/src/cdc_sump.c b/src/cdc_sump.c
new file mode 100644
index 0000000..123e72d
--- /dev/null
+++ b/src/cdc_sump.c
@@ -0,0 +1,51 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 Jaroslav Kysela <perex@perex.cz>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ */
+
+#include <pico/stdlib.h>
+
+#include "tusb.h"
+
+#include "picoprobe_config.h"
+#include "cdc_sump.h"
+
+void cdc_sump_init(void)
+{
+}
+
+#define MAX_UART_PKT 64
+void cdc_sump_task(void) {
+    uint8_t tx_buf[MAX_UART_PKT];
+    const char itf = 1;
+
+    if (tud_cdc_n_connected(itf)) {
+        if (tud_cdc_n_available(itf)) {
+            tud_cdc_n_read(itf, tx_buf, sizeof(tx_buf));
+        }
+    }
+}
+
+void cdc_sump_line_coding(cdc_line_coding_t const* line_coding) {
+    picoprobe_info("Sump new baud rate %d\n", line_coding->bit_rate);
+}
diff --git a/src/cdc_uart.c b/src/cdc_uart.c
index 8f20fef..b7a2bda 100644
--- a/src/cdc_uart.c
+++ b/src/cdc_uart.c
@@ -28,6 +28,7 @@
 #include "tusb.h"
 
 #include "picoprobe_config.h"
+#include "cdc_uart.h"
 
 void cdc_uart_init(void) {
     gpio_set_function(PICOPROBE_UART_TX, GPIO_FUNC_UART);
@@ -36,9 +37,10 @@ void cdc_uart_init(void) {
 }
 
 #define MAX_UART_PKT 64
-void cdc_task(void) {
+void cdc_uart_task(void) {
     uint8_t rx_buf[MAX_UART_PKT];
     uint8_t tx_buf[MAX_UART_PKT];
+    const char itf = 0;
 
     // Consume uart fifo regardless even if not connected
     uint rx_len = 0;
@@ -46,24 +48,22 @@ void cdc_task(void) {
         rx_buf[rx_len++] = uart_getc(PICOPROBE_UART_INTERFACE);
     }
 
-    if (tud_cdc_connected()) {
+    if (tud_cdc_n_connected(itf)) {
         // Do we have anything to display on the host's terminal?
         if (rx_len) {
-            for (uint i = 0; i < rx_len; i++) {
-                tud_cdc_write_char(rx_buf[i]);
-            }
-            tud_cdc_write_flush();
+            tud_cdc_n_write(itf, rx_buf, rx_len);
+            tud_cdc_n_write_flush(itf);
         }
 
-        if (tud_cdc_available()) {
+        if (tud_cdc_n_available(itf)) {
             // Is there any data from the host for us to tx
-            uint tx_len = tud_cdc_read(tx_buf, sizeof(tx_buf));
+            uint tx_len = tud_cdc_n_read(itf, tx_buf, sizeof(tx_buf));
             uart_write_blocking(PICOPROBE_UART_INTERFACE, tx_buf, tx_len);
         }
     }
 }
 
-void tud_cdc_line_coding_cb(uint8_t itf, cdc_line_coding_t const* line_coding) {
+void cdc_uart_line_coding(cdc_line_coding_t const* line_coding) {
     picoprobe_info("New baud rate %d\n", line_coding->bit_rate);
     uart_init(PICOPROBE_UART_INTERFACE, line_coding->bit_rate);
 }
diff --git a/src/cdc_uart.h b/src/cdc_uart.h
index 186ad50..2e70e0a 100644
--- a/src/cdc_uart.h
+++ b/src/cdc_uart.h
@@ -27,6 +27,7 @@
 #define CDC_UART_H
 
 void cdc_uart_init(void);
-void cdc_task(void);
+void cdc_uart_task(void);
+void cdc_uart_line_coding(cdc_line_coding_t const* line_coding);
 
-#endif
\ No newline at end of file
+#endif
diff --git a/src/main.c b/src/main.c
index 21439a1..48d7313 100644
--- a/src/main.c
+++ b/src/main.c
@@ -33,17 +33,26 @@
 #include "picoprobe_config.h"
 #include "probe.h"
 #include "cdc_uart.h"
+#include "cdc_sump.h"
 #include "get_serial.h"
 #include "led.h"
 
 // UART0 for Picoprobe debug
 // UART1 for picoprobe to target device
 
+void tud_cdc_line_coding_cb(uint8_t itf, cdc_line_coding_t const* line_coding) {
+    if (itf == 0)
+        cdc_uart_line_coding(line_coding);
+    else if (itf == 1)
+        cdc_sump_line_coding(line_coding);
+}
+
 int main(void) {
 
     board_init();
     usb_serial_init();
     cdc_uart_init();
+    cdc_sump_init();
     tusb_init();
     probe_init();
     led_init();
@@ -52,7 +61,8 @@ int main(void) {
 
     while (1) {
         tud_task(); // tinyusb device task
-        cdc_task();
+        cdc_uart_task();
+        cdc_sump_task();
         probe_task();
         led_task();
     }
diff --git a/src/tusb_config.h b/src/tusb_config.h
index b4dc45c..ea325a8 100644
--- a/src/tusb_config.h
+++ b/src/tusb_config.h
@@ -63,7 +63,7 @@
 
 //------------- CLASS -------------//
 #define CFG_TUD_HID             0
-#define CFG_TUD_CDC             1
+#define CFG_TUD_CDC             2
 #define CFG_TUD_MSC             0
 #define CFG_TUD_MIDI            0
 #define CFG_TUD_VENDOR          1
diff --git a/src/usb_descriptors.c b/src/usb_descriptors.c
index dd6b4f0..73c56a7 100644
--- a/src/usb_descriptors.c
+++ b/src/usb_descriptors.c
@@ -65,6 +65,8 @@ enum
   ITF_NUM_CDC_COM,
   ITF_NUM_CDC_DATA,
   ITF_NUM_PROBE,
+  ITF_NUM_CDC_SUMP_COM,
+  ITF_NUM_CDC_SUMP_DATA,
   ITF_NUM_TOTAL
 };
 
@@ -73,8 +75,12 @@ enum
 #define CDC_DATA_IN_EP_NUM 0x83
 #define PROBE_OUT_EP_NUM 0x04
 #define PROBE_IN_EP_NUM 0x85
+#define CDC_SUMP_NOTIFICATION_EP_NUM 0x86
+#define CDC_SUMP_DATA_OUT_EP_NUM 0x07
+#define CDC_SUMP_DATA_IN_EP_NUM 0x88
 
-#define CONFIG_TOTAL_LEN  (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN + TUD_VENDOR_DESC_LEN)
+#define CONFIG_TOTAL_LEN  (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN + \
+                           TUD_VENDOR_DESC_LEN + TUD_CDC_DESC_LEN)
 
 uint8_t const desc_configuration[] =
 {
@@ -84,8 +90,11 @@ uint8_t const desc_configuration[] =
   TUD_CDC_DESCRIPTOR(ITF_NUM_CDC_COM, 0, CDC_NOTIFICATION_EP_NUM, 64, CDC_DATA_OUT_EP_NUM, CDC_DATA_IN_EP_NUM, 64),
 
   // Interface 2
-  TUD_VENDOR_DESCRIPTOR(ITF_NUM_PROBE, 0, PROBE_OUT_EP_NUM, PROBE_IN_EP_NUM, 64)
+  TUD_VENDOR_DESCRIPTOR(ITF_NUM_PROBE, 0, PROBE_OUT_EP_NUM, PROBE_IN_EP_NUM, 64),
 
+  // Interface 3 + 4
+  TUD_CDC_DESCRIPTOR(ITF_NUM_CDC_SUMP_COM, 0, CDC_SUMP_NOTIFICATION_EP_NUM, 64,
+                     CDC_SUMP_DATA_OUT_EP_NUM, CDC_SUMP_DATA_IN_EP_NUM, 64)
 };
 
 // Invoked when received GET CONFIGURATION DESCRIPTOR