diff --git a/src/include/rtt_if.h b/src/include/rtt_if.h
index ceba91a7451..6f45e133f03 100644
--- a/src/include/rtt_if.h
+++ b/src/include/rtt_if.h
@@ -65,11 +65,11 @@ int rtt_if_init(void);
 /* hosted teardown */
 int rtt_if_exit(void);
 
-/* target to host: write len bytes from the buffer starting at buf. return number bytes written */
-uint32_t rtt_write(const char *buf, uint32_t len);
-/* host to target: read one character, non-blocking. return character, -1 if no character */
-int32_t rtt_getchar(void);
-/* host to target: true if no characters available for reading */
-bool rtt_nodata(void);
+/* target to host: write len bytes from the buffer on the channel starting at buf. return number bytes written */
+uint32_t rtt_write(const uint32_t channel, const char *buf, uint32_t len);
+/* host to target: read one character from the channel, non-blocking. return character, -1 if no character */
+int32_t rtt_getchar(const uint32_t channel);
+/* host to target: true if no characters available for reading in the selected channel */
+bool rtt_nodata(const uint32_t channel);
 
 #endif /* INCLUDE_RTT_IF_H */
diff --git a/src/platforms/common/stm32/rtt_if.c b/src/platforms/common/stm32/rtt_if.c
index f781918e837..f5a7fea523b 100644
--- a/src/platforms/common/stm32/rtt_if.c
+++ b/src/platforms/common/stm32/rtt_if.c
@@ -93,9 +93,10 @@ void rtt_serial_receive_callback(usbd_device *dev, uint8_t ep)
 }
 
 /* rtt host to target: read one character */
-int32_t rtt_getchar()
+int32_t rtt_getchar(const uint32_t channel)
 {
 	int retval;
+	(void)channel;
 
 	if (recv_head == recv_tail)
 		return -1;
@@ -110,14 +111,20 @@ int32_t rtt_getchar()
 }
 
 /* rtt host to target: true if no characters available for reading */
-bool rtt_nodata()
+bool rtt_nodata(const uint32_t channel)
 {
+	/* only support reading from down channel 0 */
+	if (channel != 0U)
+		return true;
 	return recv_head == recv_tail;
 }
 
 /* rtt target to host: write string */
-uint32_t rtt_write(const char *buf, uint32_t len)
+uint32_t rtt_write(const uint32_t channel, const char *buf, uint32_t len)
 {
+	/* only support writing to up channel 0 */
+	if (channel != 0U)
+		return len;
 	if (len != 0 && usbdev && usb_get_config() && gdb_serial_get_dtr()) {
 		for (uint32_t p = 0; p < len; p += CDCACM_PACKET_SIZE) {
 			uint32_t plen = MIN(CDCACM_PACKET_SIZE, len - p);
diff --git a/src/platforms/hosted/rtt_if.c b/src/platforms/hosted/rtt_if.c
index 3c5a11cf8d0..516ffe79ca0 100644
--- a/src/platforms/hosted/rtt_if.c
+++ b/src/platforms/hosted/rtt_if.c
@@ -71,8 +71,11 @@ int rtt_if_exit()
 
 /* write buffer to terminal */
 
-uint32_t rtt_write(const char *buf, uint32_t len)
+uint32_t rtt_write(const uint32_t channel, const char *buf, uint32_t len)
 {
+	/* only support writing to up channel 0 */
+	if (channel != 0U)
+		return len;
 	int unused = write(1, buf, len);
 	(void)unused;
 	return len;
@@ -80,10 +83,11 @@ uint32_t rtt_write(const char *buf, uint32_t len)
 
 /* read character from terminal */
 
-int32_t rtt_getchar()
+int32_t rtt_getchar(const uint32_t channel)
 {
 	char ch;
 	int len;
+	(void)channel;
 	len = read(0, &ch, 1);
 	if (len == 1)
 		return ch;
@@ -92,8 +96,9 @@ int32_t rtt_getchar()
 
 /* true if no characters available */
 
-bool rtt_nodata()
+bool rtt_nodata(const uint32_t channel)
 {
+	(void)channel;
 	return false;
 }
 
@@ -113,23 +118,28 @@ int rtt_if_exit()
 
 /* write buffer to terminal */
 
-uint32_t rtt_write(const char *buf, uint32_t len)
+uint32_t rtt_write(const uint32_t channel, const char *buf, uint32_t len)
 {
+	/* only support writing to up channel 0 */
+	if (channel != 0U)
+		return len;
 	write(1, buf, len);
 	return len;
 }
 
 /* read character from terminal */
 
-int32_t rtt_getchar()
+int32_t rtt_getchar(const uint32_t channel)
 {
+	(void)channel;
 	return -1;
 }
 
 /* true if no characters available */
 
-bool rtt_nodata()
+bool rtt_nodata(const uint32_t channel)
 {
+	(void)channel;
 	return false;
 }
 
diff --git a/src/platforms/launchpad-icdi/rtt_if.c b/src/platforms/launchpad-icdi/rtt_if.c
index 57544cf5652..a3983fd54e8 100644
--- a/src/platforms/launchpad-icdi/rtt_if.c
+++ b/src/platforms/launchpad-icdi/rtt_if.c
@@ -93,9 +93,10 @@ void rtt_serial_receive_callback(usbd_device *dev, uint8_t ep)
 }
 
 /* rtt host to target: read one character */
-int32_t rtt_getchar()
+int32_t rtt_getchar(const uint32_t channel)
 {
 	int retval;
+	(void)channel;
 
 	if (recv_head == recv_tail)
 		return -1;
@@ -110,14 +111,20 @@ int32_t rtt_getchar()
 }
 
 /* rtt host to target: true if no characters available for reading */
-bool rtt_nodata()
+bool rtt_nodata(const uint32_t channel)
 {
+	/* only support reading from down channel 0 */
+	if (channel != 0U)
+		return true;
 	return recv_head == recv_tail;
 }
 
 /* rtt target to host: write string */
-uint32_t rtt_write(const char *buf, uint32_t len)
+uint32_t rtt_write(const uint32_t channel, const char *buf, uint32_t len)
 {
+	/* only support writing to up channel 0 */
+	if (channel != 0U)
+		return len;
 	if (len != 0 && usbdev && usb_get_config() && gdb_serial_get_dtr()) {
 		for (uint32_t p = 0; p < len; p += CDCACM_PACKET_SIZE) {
 			uint32_t plen = MIN(CDCACM_PACKET_SIZE, len - p);
diff --git a/src/rtt.c b/src/rtt.c
index 88f2039a635..3e4b2e40e2c 100644
--- a/src/rtt.c
+++ b/src/rtt.c
@@ -222,8 +222,13 @@ static void find_rtt(target_s *const cur_target)
 /* poll if host has new data for target */
 static rtt_retval_e read_rtt(target_s *const cur_target, const uint32_t i)
 {
+	/* down buffers are located in the rtt_channel array after the
+	 * up buffers. subtract the index from the total number of
+	 * up buffers to get the down buffer number. */
+	uint32_t channel = i - rtt_num_up_chan;
+
 	/* copy data from recv_buf to target rtt 'down' buffer */
-	if (rtt_nodata())
+	if (rtt_nodata(channel))
 		return RTT_IDLE;
 
 	if (cur_target == NULL || rtt_channel[i].buf_addr == 0 || rtt_channel[i].buf_size == 0)
@@ -237,7 +242,7 @@ static rtt_retval_e read_rtt(target_s *const cur_target, const uint32_t i)
 		const uint32_t next_head = (rtt_channel[i].head + 1U) % rtt_channel[i].buf_size;
 		if (rtt_channel[i].tail == next_head)
 			break;
-		const int ch = rtt_getchar();
+		const int ch = rtt_getchar(channel);
 		if (ch == -1)
 			break;
 		if (target_mem32_write(cur_target, rtt_channel[i].buf_addr + rtt_channel[i].head, &ch, 1))
@@ -320,7 +325,7 @@ static rtt_retval_e print_rtt(target_s *const cur_target, const uint32_t i)
 		return RTT_ERR;
 
 	/* write buffer to usb */
-	rtt_write(xmit_buf, bytes_read);
+	rtt_write(i, xmit_buf, bytes_read);
 
 	return RTT_OK;
 }