diff --git a/libfreefare/freefare_internal.h b/libfreefare/freefare_internal.h
index 0b66fcf..93aa1ee 100644
--- a/libfreefare/freefare_internal.h
+++ b/libfreefare/freefare_internal.h
@@ -231,6 +231,14 @@ struct mifare_ultralight_tag {
     uint8_t buffer_name[size]; \
     size_t __##buffer_name##_n = 0
 
+/*
+ * Create a wrapper for an existing buffer.
+ * BEWARE!  It eats children!
+ */
+#define BUFFER_ALIAS(buffer_name, origin) \
+    uint8_t *buffer_name = (void *)origin; \
+    size_t __##buffer_name##_n = 0;
+
 #define BUFFER_SIZE(buffer_name) (__##buffer_name##_n)
 
 #define BUFFER_CLEAR(buffer_name) (__##buffer_name##_n = 0)
diff --git a/libfreefare/mifare_classic.c b/libfreefare/mifare_classic.c
index d2e2e2f..afd3f36 100644
--- a/libfreefare/mifare_classic.c
+++ b/libfreefare/mifare_classic.c
@@ -61,7 +61,9 @@
 #include <string.h>
 #include <strings.h>
 
-#include <nfc/nfc.h>
+#ifdef WITH_DEBUG
+#  include <libutil.h>
+#endif
 
 #include <freefare.h>
 #include "freefare_internal.h"
@@ -75,6 +77,20 @@
 #define MC_INCREMENT      0xC1
 #define MC_RESTORE        0xC2
 
+#define CLASSIC_TRANSCEIVE(tag, msg, res) CLASSIC_TRANSCEIVE_EX(tag, msg, res, 0)
+
+#define CLASSIC_TRANSCEIVE_EX(tag, msg, res, disconnect) \
+    do { \
+	errno = 0; \
+	DEBUG_XFER (msg, __##msg##_n, "===> "); \
+	if (!(nfc_initiator_transceive_dep_bytes (tag->device, msg, __##msg##_n, res, &__##res##_n))) { \
+	    if (disconnect) \
+		tag->active = false; \
+	    return errno = EIO, -1; \
+	} \
+	DEBUG_XFER (res, __##res##_n, "<=== "); \
+    } while (0)
+
 /* Public Key A value of NFC Forum sectors */
 const MifareClassicKey mifare_classic_nfcforum_public_key_a = {
     0xd3, 0xf7, 0xd3, 0xf7, 0xd3, 0xf7
@@ -249,19 +265,19 @@ mifare_classic_authenticate (MifareTag tag, const MifareClassicBlockNumber block
     ASSERT_ACTIVE (tag);
     ASSERT_MIFARE_CLASSIC (tag);
 
-    unsigned char command[12];
-    command[0] = (key_type == MFC_KEY_A) ? MC_AUTH_A : MC_AUTH_B;
-    command[1] = block;
-    memcpy (&(command[2]), key, 6);
-    memcpy (&(command[8]), tag->info.abtUid, 4);
+    BUFFER_INIT (cmd, 12);
+    BUFFER_INIT (res, 1);
 
-    // Send command
-    size_t n;
-    if (!(nfc_initiator_transceive_dep_bytes (tag->device, command, sizeof (command), NULL, &n))) {
-	tag->active = false; /* Tag is no more active if authentication failed. */
-	errno = EIO;
-	return -1;
-    }
+    if (key_type == MFC_KEY_A)
+	BUFFER_APPEND (cmd, MC_AUTH_A);
+    else
+	BUFFER_APPEND (cmd, MC_AUTH_B);
+
+    BUFFER_APPEND(cmd, block);
+    BUFFER_APPEND_BYTES (cmd, key, 6);
+    BUFFER_APPEND_BYTES (cmd, tag->info.abtUid, 4);
+
+    CLASSIC_TRANSCEIVE_EX (tag, cmd, res, 1);
 
     MIFARE_CLASSIC(tag)->cached_access_bits.sector_trailer_block_number = -1;
     MIFARE_CLASSIC(tag)->cached_access_bits.sector_access_bits = 0x00;
@@ -280,16 +296,13 @@ mifare_classic_read (MifareTag tag, const MifareClassicBlockNumber block, Mifare
     ASSERT_ACTIVE (tag);
     ASSERT_MIFARE_CLASSIC (tag);
 
-    unsigned char command[2];
-    command[0] = MC_READ;
-    command[1] = block;
+    BUFFER_INIT (cmd, 2);
+    BUFFER_ALIAS (res, data);
 
-    // Send command
-    size_t n;
-    if (!(nfc_initiator_transceive_dep_bytes (tag->device, command, sizeof (command), *data, &n))) {
-	errno = EIO;
-	return -1;
-    }
+    BUFFER_APPEND (cmd, MC_READ);
+    BUFFER_APPEND (cmd, block);
+
+    CLASSIC_TRANSCEIVE (tag, cmd, res);
 
     return 0;
 }
@@ -354,17 +367,14 @@ mifare_classic_write (MifareTag tag, const MifareClassicBlockNumber block, const
     ASSERT_ACTIVE (tag);
     ASSERT_MIFARE_CLASSIC (tag);
 
-    unsigned char command[2 + sizeof (MifareClassicBlock)];
-    command[0] = MC_WRITE;
-    command[1] = block;
-    memcpy (&(command[2]), data, sizeof (MifareClassicBlock));
+    BUFFER_INIT (cmd, 2 + sizeof (MifareClassicBlock));
+    BUFFER_INIT (res, 1);
 
-    // Send command
-    size_t n;
-    if (!(nfc_initiator_transceive_dep_bytes (tag->device, command, sizeof (command), NULL, &n))) {
-	errno = EIO;
-	return -1;
-    }
+    BUFFER_APPEND (cmd, MC_WRITE);
+    BUFFER_APPEND (cmd, block);
+    BUFFER_APPEND_BYTES (cmd, data, sizeof (MifareClassicBlock));
+
+    CLASSIC_TRANSCEIVE (tag, cmd, res);
 
     // No result.  The MIFARE tag just ACKed.
     return 0;
@@ -380,18 +390,14 @@ mifare_classic_increment (MifareTag tag, const MifareClassicBlockNumber block, c
     ASSERT_ACTIVE (tag);
     ASSERT_MIFARE_CLASSIC (tag);
 
-    unsigned char command[6];
-    command[0] = MC_INCREMENT;
-    command[1] = block;
-    uint32_t le_amount = htole32 (amount);
-    memcpy(&(command[2]), &le_amount, sizeof (le_amount));
+    BUFFER_INIT (cmd, 6);
+    BUFFER_INIT (res, 1);
 
-    // Send command
-    size_t n;
-    if (!(nfc_initiator_transceive_dep_bytes (tag->device, command, sizeof (command), NULL, &n))) {
-	errno = EIO;
-	return -1;
-    }
+    BUFFER_APPEND (cmd, MC_INCREMENT);
+    BUFFER_APPEND (cmd, block);
+    BUFFER_APPEND_LE (cmd, amount, 4, sizeof (amount));
+
+    CLASSIC_TRANSCEIVE (tag, cmd, res);
 
     // No result.  The MIFARE tag just ACKed.
     return 0;
@@ -407,18 +413,14 @@ mifare_classic_decrement (MifareTag tag, const MifareClassicBlockNumber block, c
     ASSERT_ACTIVE (tag);
     ASSERT_MIFARE_CLASSIC (tag);
 
-    unsigned char command[6];
-    command[0] = MC_DECREMENT;
-    command[1] = block;
-    uint32_t le_amount = htole32 (amount);
-    memcpy(&(command[2]), &le_amount, sizeof (le_amount));
+    BUFFER_INIT (cmd, 6);
+    BUFFER_INIT (res, 1);
 
-    // Send command
-    size_t n;
-    if (!(nfc_initiator_transceive_dep_bytes (tag->device, command, sizeof (command), NULL, &n))) {
-	errno = EIO;
-	return -1;
-    }
+    BUFFER_APPEND (cmd, MC_DECREMENT);
+    BUFFER_APPEND (cmd, block);
+    BUFFER_APPEND_LE (cmd, amount, 4, sizeof (amount));
+
+    CLASSIC_TRANSCEIVE (tag, cmd, res);
 
     // No result.  The MIFARE tag just ACKed.
     return 0;
@@ -436,18 +438,19 @@ mifare_classic_restore (MifareTag tag, const MifareClassicBlockNumber block)
     /*
      * Same length as the increment and decrement commands but only the first
      * two bytes are actually used.  The 4 bytes after the block number are
-     * meaningless but required (thus left uninitialized).
+     * meaningless but required (NULL-filled).
      */
-    unsigned char command[6];
-    command[0] = MC_RESTORE;
-    command[1] = block;
+    BUFFER_INIT (cmd, 6);
+    BUFFER_INIT (res, 1);
 
-    // Send command
-    size_t n;
-    if (!(nfc_initiator_transceive_dep_bytes (tag->device, command, sizeof (command), NULL, &n))) {
-	errno = EIO;
-	return -1;
-    }
+    BUFFER_APPEND (cmd, MC_RESTORE);
+    BUFFER_APPEND (cmd, block);
+    BUFFER_APPEND (cmd, 0x00);
+    BUFFER_APPEND (cmd, 0x00);
+    BUFFER_APPEND (cmd, 0x00);
+    BUFFER_APPEND (cmd, 0x00);
+
+    CLASSIC_TRANSCEIVE (tag, cmd, res);
 
     // No result.  The MIFARE tag just ACKed.
     return 0;
@@ -462,17 +465,13 @@ mifare_classic_transfer (MifareTag tag, const MifareClassicBlockNumber block)
     ASSERT_ACTIVE (tag);
     ASSERT_MIFARE_CLASSIC (tag);
 
-    unsigned char command[2];
-    command[0] = MC_TRANSFER;
-    command[1] = block;
+    BUFFER_INIT (cmd, 2);
+    BUFFER_INIT (res, 1);
 
-    // Send command
-    size_t n;
-    unsigned char buffer[1];
-    if (!(nfc_initiator_transceive_dep_bytes (tag->device, command, sizeof (command), buffer, &n))) {
-	errno = EIO;
-	return -1;
-    }
+    BUFFER_APPEND (cmd, MC_TRANSFER);
+    BUFFER_APPEND (cmd, block);
+
+    CLASSIC_TRANSCEIVE (tag, cmd, res);
 
     // FIXME: The receive command returns data. Should be checked.
     return 0;
diff --git a/libfreefare/mifare_ultralight.c b/libfreefare/mifare_ultralight.c
index 4378862..f045716 100644
--- a/libfreefare/mifare_ultralight.c
+++ b/libfreefare/mifare_ultralight.c
@@ -30,17 +30,33 @@
 
 #include "config.h"
 
+#if defined(HAVE_SYS_TYPES_H)
+#  include <sys/types.h>
+#endif
+
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 
-#include <nfc/nfc.h>
+#ifdef WITH_DEBUG
+#  include <libutil.h>
+#endif
 
 #include <freefare.h>
 #include "freefare_internal.h"
 
 #define ASSERT_VALID_PAGE(page) do { if (page >= MIFARE_ULTRALIGHT_PAGE_COUNT) return errno = EINVAL, -1; } while (0)
 
+#define ULTRALIGHT_TRANSCEIVE(tag, msg, res) \
+    do { \
+	errno = 0; \
+	DEBUG_XFER (msg, __##msg##_n, "===> "); \
+	if (!(nfc_initiator_transceive_dep_bytes (tag->device, msg, __##msg##_n, res, &__##res##_n))) { \
+	    return errno = EIO, -1; \
+	} \
+	DEBUG_XFER (res, __##res##_n, "<=== "); \
+    } while (0)
+
 
 /*
  * Memory management functions.
@@ -132,15 +148,13 @@ mifare_ultralight_read (MifareTag tag, MifareUltralightPageNumber page, MifareUl
     ASSERT_VALID_PAGE (page);
 
     if (!MIFARE_ULTRALIGHT(tag)->cached_pages[page]) {
-	uint8_t cmd[2];
-	cmd[0] = 0x30;
-	cmd[1] = page;
+	BUFFER_INIT (cmd, 2);
+	BUFFER_ALIAS (res, MIFARE_ULTRALIGHT(tag)->cache[page]);
 
-	size_t n;
-	if (!(nfc_initiator_transceive_dep_bytes (tag->device, cmd, sizeof (cmd), MIFARE_ULTRALIGHT(tag)->cache[page], &n))) {
-	    errno = EIO;
-	    return -1;
-	}
+	BUFFER_APPEND (cmd, 0x30);
+	BUFFER_APPEND (cmd, page);
+
+	ULTRALIGHT_TRANSCEIVE (tag, cmd, res);
 
 	/* Handle wrapped pages */
 	for (int i = MIFARE_ULTRALIGHT_PAGE_COUNT; i <= page + 3; i++) {