diff --git a/libnfc/chips/pn53x-internal.h b/libnfc/chips/pn53x-internal.h
index c43934a..e4869cd 100644
--- a/libnfc/chips/pn53x-internal.h
+++ b/libnfc/chips/pn53x-internal.h
@@ -81,32 +81,38 @@
 #define TgGetTargetStatus 0x8A
 
 /** @note PN53x's normal frame:
+ * See the PN532 (firmware) user manual, section 6.2.1.1: Normal information
+ * frame, figure 13. Normal information frame, page 28 rev. 02 - 2007-11-07.
  *
- *   .-- Start
- *   |   .-- Packet length
- *   |   |  .-- Length checksum
- *   |   |  |  .-- Direction (D4 Host to PN, D5 PN to Host)
- *   |   |  |  |  .-- Code
- *   |   |  |  |  |  .-- Packet checksum
- *   |   |  |  |  |  |  .-- Postamble
- *   V   |  |  |  |  |  |
- * ----- V  V  V  V  V  V
- * 00 FF 02 FE D4 02 2A 00
+ * .-- Preamble
+ * |    .-- Start
+ * |    |   .-- Packet length
+ * |    |   |  .-- Length checksum
+ * |    |   |  |  .-- Direction (D4 Host to PN, D5 PN to Host)
+ * |    |   |  |  |  .-- Code
+ * |    |   |  |  |  |  .-- Packet checksum
+ * |    |   |  |  |  |  |  .-- Postamble
+ * |    V   |  |  |  |  |  |
+ * V  ----- V  V  V  V  V  V
+ * 00 00 FF 02 FE D4 02 2A 00
  */
 
 /** @note PN53x's extended frame:
+ * See the PN532 (firmware) user manual, section 6.2.1.2: Extended information
+ * frame, figure 14. Normal information frame, page 29 rev. 02 - 2007-11-07.
  *
- *   .-- Start
- *   |     .-- Fixed to FF to enable extended frame
- *   |     |     .-- Packet length
- *   |     |     |   .-- Length checksum
- *   |     |     |   |  .-- Direction (D4 Host to PN, D5 PN to Host)
- *   |     |     |   |  |  .-- Code
- *   |     |     |   |  |  |  .-- Packet checksum
- *   |     |     |   |  |  |  |  .-- Postamble
- *   V     V     V   |  |  |  |  |
- * ----- ----- ----- V  V  V  V  V
- * 00 FF FF FF 00 02 FE D4 02 2A 00
+ * .-- Preamble
+ * |    .-- Start
+ * |    |     .-- Fixed to FF to enable extended frame
+ * |    |     |     .-- Packet length
+ * |    |     |     |   .-- Length checksum
+ * |    |     |     |   |  .-- Direction (D4 Host to PN, D5 PN to Host)
+ * |    |     |     |   |  |  .-- Code
+ * |    |     |     |   |  |  |  .-- Packet checksum
+ * |    |     |     |   |  |  |  |  .-- Postamble
+ * |    V     V     V   |  |  |  |  |
+ * V  ----- ----- ----- V  V  V  V  V
+ * 00 00 FF FF FF 00 02 FE D4 02 2A 00
  */
 
 /**
diff --git a/libnfc/drivers/pn532_i2c.c b/libnfc/drivers/pn532_i2c.c
index b62c7de..fe3345c 100644
--- a/libnfc/drivers/pn532_i2c.c
+++ b/libnfc/drivers/pn532_i2c.c
@@ -75,6 +75,10 @@ const struct timespec rdyDelay = {
   .tv_nsec = PN532_RDY_LOOP_DELAY * 1000 * 1000
 };
 
+/* preamble and start bytes, see pn532-internal.h for details */
+const uint8_t pn53x_preamble_and_start[] = { 0x00, 0x00, 0xff };
+#define PN53X_PREAMBLE_AND_START_LEN	(sizeof(pn53x_preamble_and_start) / sizeof(pn53x_preamble_and_start[0]))
+
 /* Private Functions Prototypes */
 
 static nfc_device *pn532_i2c_open(const nfc_context *context, const nfc_connstring connstring);
@@ -334,9 +338,10 @@ pn532_i2c_send(nfc_device *pnd, const uint8_t *pbtData, const size_t szData, int
       break;
   };
 
-  uint8_t abtFrame[PN532_BUFFER_LEN] = { 0x00, 0x00, 0xff };       // Every packet must start with "00 00 ff"
+  uint8_t abtFrame[PN532_BUFFER_LEN];
   size_t szFrame = 0;
 
+  memcpy(abtFrame, pn53x_preamble_and_start, PN53X_PREAMBLE_AND_START_LEN);	// Every packet must start with the preamble and start bytes.
   if ((res = pn53x_build_frame(abtFrame, &szFrame, pbtData, szData)) < 0) {
     pnd->last_error = res;
     return pnd->last_error;
@@ -477,9 +482,7 @@ pn532_i2c_receive(nfc_device *pnd, uint8_t *pbtData, const size_t szDataLen, int
     goto error;
   }
 
-  const uint8_t pn53x_preamble[3] = { 0x00, 0x00, 0xff };
-
-  if (0 != (memcmp(frameBuf, pn53x_preamble, 3))) {
+  if (0 != (memcmp(frameBuf, pn53x_preamble_and_start, PN53X_PREAMBLE_AND_START_LEN))) {
     log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_ERROR, "%s", "Frame preamble+start code mismatch");
     pnd->last_error = NFC_EIO;
     goto error;