diff --git a/demo/fw/src/main.c b/demo/fw/src/main.c
index c5734f3..e8710bd 100644
--- a/demo/fw/src/main.c
+++ b/demo/fw/src/main.c
@@ -297,14 +297,16 @@ int main(void)
     con_printf("loop");
     while (23) {
 
+        /*
         uint8_t rd_buf[128];
         ssize_t rv = con_read_until(rd_buf, sizeof(rd_buf), '\n');
         if (rv < 0) {
             con_printf("USART rx error\r\n");
         }
         con_printf("Received %d bytes: %s\r\n", rv, rd_buf);
+        */
 
-        con_printf(" #%u", i);
+        con_printf_blocking(" #%u", i);
         if (k == 0)
             spif_printf(&spif, "\33[1m");
         if (k == 1)
@@ -315,7 +317,7 @@ int main(void)
             spif_printf(&spif, "\033[3%dm", k-4+1);
         if (k >= 12 && k < 20)
             spif_printf(&spif, "\033[9%dm", k-12+1);
-        spif_printf(&spif, "loop #%u  \033[4%dmloop #u  \033[10%dmloop #u\033[0m\n", i, k%8, (k+1)%8);
+        spif_printf(&spif, "loop #%u  \033[4%dmloop #%u  \033[10%dmloop #%u\033[0m\n", i, k%8, (k+1)%8);
         i++;
         k = (k + 1) % 40;
         if (k == 0) {
@@ -323,17 +325,32 @@ int main(void)
 
             uint8_t buf[4096];
             spif_capture_read(&spif, sizeof(buf), buf);
-            con_printf("\r\n");
-            con_printf("\r\n");
-            con_printf("buffer capture:\r\n");
-            for (size_t e=0; e<sizeof(buf); e += 16) {
+            con_printf_blocking("\r\n");
+            con_printf_blocking("\r\n");
+            con_printf_blocking("buffer capture:\r\n");
+            for (size_t e=0; e<sizeof(buf); e += 27) {
                 uint8_t *p = buf + e;
-                con_printf("    %02x %02x %02x %02x %02x %02x %02x %02x  %02x %02x %02x %02x %02x %02x %02x %02x\r\n",
-                        p[0x00], buf[0x01], buf[0x02], buf[0x03], buf[0x04], buf[0x05], buf[0x06], buf[0x07],
-                        p[0x08], buf[0x09], buf[0x0a], buf[0x0b], buf[0x0c], buf[0x0d], buf[0x0e], buf[0x0f]);
+                con_printf_blocking("   ");
+                for (size_t j=0; j<27 && e+j < sizeof(buf); j++) {
+                    if (j%3 == 0)
+                        con_printf_blocking("\033[91m");
+                    else if (j%3 == 1)
+                        con_printf_blocking("\033[92m");
+                    else if (j%3 == 2)
+                        con_printf_blocking("\033[94m");
+
+                    con_printf_blocking("%02x", p[j]);
+
+                    if (j == 9-1 || j == 18-1)
+                        con_printf_blocking("  ");
+                    else if (j == 27-1)
+                        con_printf_blocking("\033[0m\r\n");
+                    else if (j > 0 && j%3 == 2)
+                        con_printf_blocking(" ");
+                }
             }
-            con_printf("\r\n");
-            con_printf("loop");
+            con_printf_blocking("\033[0m\r\n");
+            con_printf_blocking("loop");
         }
 
         for (int j=0; j<1000000; j++) {
diff --git a/demo/fw/src/serial.c b/demo/fw/src/serial.c
index ad7b5fa..cb244b3 100644
--- a/demo/fw/src/serial.c
+++ b/demo/fw/src/serial.c
@@ -262,7 +262,6 @@ int usart_printf(volatile struct usart_desc *us, const char *fmt, ...) {
     va_list va;
     va_start(va, fmt);
     tfp_format((void *)us, usart_putc_nonblocking_tpf, fmt, va);
-    return usart_flush(us);
 }
 
 int usart_printf_blocking_va(volatile struct usart_desc *us, const char *fmt, va_list va) {