diff --git a/Core/Src/main.c b/Core/Src/main.c
index 854e4f1..8169a02 100644
--- a/Core/Src/main.c
+++ b/Core/Src/main.c
@@ -22,6 +22,7 @@
 /* Private includes ----------------------------------------------------------*/
 /* USER CODE BEGIN Includes */
 #include "printf.h"
+#include <stm32f4xx_it.h>
 #include <usart2_it.h>
 #include <usart6_it.h>
 #include "usart1_it.h"
@@ -135,24 +136,67 @@ int main(void) {
    /* USER CODE BEGIN WHILE */
    while (1) {
       static uint32_t Tick10msRef = 0;
+      /* per-second and total byte counters */
+      static uint32_t bytes_2to6 = 0;
+      static uint32_t bytes_6to2 = 0;
+      static uint32_t total_2to6 = 0;
+      static uint32_t total_6to2 = 0;
       if (TickChk(&Tick10msRef, 10)) {
       }
 
       static uint32_t Tick1secRef = 0;
       if (TickChk(&Tick1secRef, 1000)) {
          LED2_Toggle();
+         /* print per-second data rates and cumulative totals */
+         printf("OUT:%5u IN:%5u B/s (Total:%u/%u)\n", (unsigned) bytes_2to6, (unsigned) bytes_6to2, (unsigned) total_2to6, (unsigned) total_6to2);
+         /* reset per-second counters */
+         bytes_2to6 = 0;
+         bytes_6to2 = 0;
       }
 
       int c;
 
+      c = Usart1_GetByte();
+      if (c != -1) {          // new incoming data
+/*
+         switch (c) {
+         case '1':
+            printf("Send 800 bytes to UART1\n");
+            for (int i = 0; i < 800; i++) {
+               Usart1_PutByte((i % 10) + '0');
+            }
+            break;
+         case '2':
+            printf("Send 800 bytes to UART2\n");
+            for (int i = 0; i < 800; i++) {
+               Usart2_PutByte((i % 20) + 'A');
+            }
+            break;
+         case '6':
+            printf("Send 800 bytes to UART6\n");
+            for (int i = 0; i < 800; i++) {
+               Usart6_PutByte((i % 20) + 'a');
+            }
+            break;
+         default: // echo back
+            Usart1_PutByte(c);
+            break;
+         }
+*/
+      }
+
       c = Usart2_GetByte();
-      if (c != -1) {// new incoming data
-         Usart6_PutByte(c);// UART2rx --> UART6tx
+      if (c != -1) {          // new incoming data
+         Usart6_PutByte(c);   // UART2rx --> UART6tx
+         bytes_2to6++;
+         total_2to6++;
       }
 
       c = Usart6_GetByte();
-      if (c != -1) {// new incoming data
-         Usart2_PutByte(c);// UART6rx --> UART2tx
+      if (c != -1) {          // new incoming data
+         Usart2_PutByte(c);   // UART6rx --> UART2tx
+         bytes_6to2++;
+         total_6to2++;
       }
 
       /* USER CODE END WHILE */