Add new miller decoder (not working yet)

Vastly improve timing through CPU cycle counting. Jitter is now like 40ns (the SSC_DATA edge detection fuzziness)  in 2 main clusters 4 CPU cycles (83ns) apart, plus an occasional glitch adding 4 CPU cycles in either direction


git-svn-id: https://svn.openpcd.org:2342/trunk@385 6dc7ffe9-61d6-0310-9af1-9938baff3ed1

1 files changed, 112 insertions, 0 deletions

diff --git a/openpicc/application/iso14443a_miller.c b/openpicc/application/iso14443a_miller.c
new file mode 100644
index 0000000..deb9a8a
--- /dev/null
+++ b/openpicc/application/iso14443a_miller.c
@@ -0,0 +1,112 @@
+/* ISO14443A Manchester encoder for OpenPICC
+ * (C) 2007 by Henryk Plötz <henryk@ploetzli.ch>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by 
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ */
+
+#include <openpicc.h>
+#include <FreeRTOS.h>
+
+#include <string.h>
+
+#include "iso14443_layer3a.h"
+#include "usb_print.h"
+#include "cmd.h"
+
+#ifdef FOUR_TIMES_OVERSAMPLING
+#define OVERSAMPLING_RATE	4
+
+/* definitions for four-times oversampling */
+#define SEQ_X	0x4
+#define SEQ_Y	0x0
+#define SEQ_Z	0x1
+#else
+#define OVERSAMPLING_RATE	2
+#define SEQ_X   0x2
+#define SEQ_Y   0x0
+#define SEQ_Z   0x1
+#endif
+
+enum miller_sequence {
+	SEQUENCE_X,
+	SEQUENCE_Y,
+	SEQUENCE_Z,
+};
+
+#define BIT_ENDMARKER -1
+
+int iso14443a_decode_miller(iso14443_frame *frame, 
+	const u_int8_t *sample_buf, const u_int16_t sample_buf_len)
+{
+	signed int i, j, bit = 0, last_bit = 0;
+	enum miller_sequence current_seq;
+	unsigned int bitpos = 0;
+	
+	memset(frame, 0, sizeof(frame));
+	frame->type = TYPE_A;
+	frame->parameters.a.parity = GIVEN_PARITY;
+	
+	for(i=0; i<sample_buf_len && bit != BIT_ENDMARKER; i++) {
+		for(j=0; j<(signed)(sizeof(sample_buf[0])*8)/OVERSAMPLING_RATE && bit != BIT_ENDMARKER; j++) {
+			int sample = (sample_buf[i]>>(j*OVERSAMPLING_RATE)) & ~(~0 << OVERSAMPLING_RATE);
+			switch(sample) {
+				case SEQ_X: current_seq = SEQUENCE_X; break;
+				case SEQ_Y: current_seq = SEQUENCE_Y; break;
+				case SEQ_Z: current_seq = SEQUENCE_Z; break;
+				default: current_seq = SEQUENCE_Y;
+			}
+			
+			switch(current_seq) {
+				case SEQ_X:
+				DumpStringToUSB("X");
+					bit = 1; break;
+				case SEQ_Y: /* Fall-through to SEQ_Z */
+				DumpStringToUSB("Y");
+					if(last_bit == 0) {
+						bit = BIT_ENDMARKER;
+						break;
+					}
+				case SEQ_Z:
+				DumpStringToUSB("Z");
+					bit = 0; break;
+			}
+			
+			switch(bit) {
+				case BIT_ENDMARKER:
+					bitpos--;
+					break;
+				case 0: /* Fall-through */
+				case 1: {
+					int bytepos = bitpos/9;
+					if(bitpos % 9 == 8) { /* Parity bit */
+						frame->parity[ bytepos/8 ] |= (bit<<(bytepos%8));
+					} else {
+						frame->data[ bytepos ] |= (bit<<(bitpos%9));
+					}
+				}
+			}
+			
+			last_bit = bit;
+			bitpos++;
+		}
+	}
+	
+	frame->numbytes = bitpos/9;
+	frame->numbits = bitpos%9;
+	DumpStringToUSB("\n\r");
+	
+	return 0;
+}