diff --git a/panic/panic.c b/panic/panic.c
index c0206b7..994ed8b 100644
--- a/panic/panic.c
+++ b/panic/panic.c
@@ -6,9 +6,10 @@ panic (pio_t led_error_pio, unsigned int error_code)
 {
     unsigned int i;
 
-    pio_config_set (led_error_pio, PIO_OUTPUT_LOW);
-#ifndef LED_ACTIVE
+#ifdef LED_ACTIVE
     pio_output_set (led_error_pio, LED_ACTIVE);
+#else
+    pio_config_set (led_error_pio, PIO_OUTPUT_LOW);
 #endif
 
     while (1)
diff --git a/tty/tty.c b/tty/tty.c
index c1fbcc4..d4e5dbf 100644
--- a/tty/tty.c
+++ b/tty/tty.c
@@ -15,11 +15,8 @@
 #include "tty.h"
 #include "sys.h"
 #include "errno.h"
-#include <ctype.h>
 #include <stdlib.h>
-#include <stdio.h>
 #include <stdarg.h>
-#include <string.h>
 
 
 struct tty_struct
diff --git a/usb_cdc/usb_cdc.c b/usb_cdc/usb_cdc.c
index f0cc61f..c31aeac 100644
--- a/usb_cdc/usb_cdc.c
+++ b/usb_cdc/usb_cdc.c
@@ -2,7 +2,6 @@
 #include "usb_cdc.h"
 #include "usb_dsc.h"
 #include "usb.h"
-#include <stdlib.h>
 
 
 /* CDC communication device class.
@@ -22,10 +21,6 @@
 #define USB_CURRENT_MA 100
 #endif
 
-#ifndef USB_CDC_TX_RING_SIZE
-#define USB_CDC_TX_RING_SIZE 80
-#endif
-
 
 #ifndef MIN
 #define MIN(a, b) (((a) < (b)) ? (a) : (b))
@@ -343,11 +338,7 @@ usb_cdc_init (const usb_cdc_cfg_t *cfg)
     dev->writing = 0;
     dev->connected = 0;
 
-    buffer = malloc (USB_CDC_TX_RING_SIZE);
-    if (!buffer)
-        return 0;
-
-    ring_init (&dev->tx_ring, buffer, USB_CDC_TX_RING_SIZE);
+    ring_init (&dev->tx_ring, dev->tx_ring_buffer, USB_CDC_TX_RING_SIZE);
 
     dev->usb = usb_init (&usb_cdc_descriptors,
                          (void *)usb_cdc_request_handler);
diff --git a/usb_cdc/usb_cdc.h b/usb_cdc/usb_cdc.h
index 0fa70e0..6e90fbb 100644
--- a/usb_cdc/usb_cdc.h
+++ b/usb_cdc/usb_cdc.h
@@ -11,10 +11,16 @@ extern "C" {
 #include "ring.h"
     
 
+#ifndef USB_CDC_TX_RING_SIZE
+#define USB_CDC_TX_RING_SIZE 80
+#endif
+
+
 typedef struct usb_cdc_struct
 {
     usb_t usb;
     ring_t tx_ring;
+    uint8_t tx_ring_buffer[USB_CDC_TX_RING_SIZE];
     uint32_t read_timeout_us;
     uint32_t write_timeout_us;
     volatile bool writing;