added mdc1200 packet encoder

mdc1200.c

@@ -0,0 +1,150 @@
+
+#include <string.h>
+
+#include "mdc1200.h"
+
+uint16_t flip_crc(const uint16_t crc, const unsigned int bit_num)
+{
+	uint16_t i;
+	uint16_t bit;
+	uint16_t crc_out;
+	for (i = 1u << (bit_num - 1), bit = 1u, crc_out = 0u; i > 0u; i >>= 1)
+	{
+		if (crc & i)
+			 crc_out |= bit;
+		bit <<= 1;
+	}
+	return crc_out;
+}
+
+uint16_t compute_crc(const uint8_t *data, const unsigned int data_len)
+{
+	unsigned int i;
+	uint16_t crc = 0x0000;
+
+	for (i = 0; i < data_len; i++)
+	{
+		unsigned int mask;
+		const uint16_t c = flip_crc(*data++, 8);
+		for (mask = 0x80; mask > 0; mask >>= 1)
+		{
+			uint16_t bit = crc & 0x8000;
+			crc <<= 1;
+			if (c & mask)
+				bit ^= 0x8000;
+			if (bit)
+				crc ^= 0x1021;
+		}
+	}
+
+	return ~flip_crc(crc, 16);
+}
+
+uint8_t * encode_data(uint8_t *data)
+{
+	unsigned int i;
+	unsigned int k;
+	unsigned int m;
+	int      csr[7];
+	int      lbits[112];
+
+	uint16_t ccrc = compute_crc(data, 4);
+
+	data[4] = (ccrc >> 0) & 0x00ff;
+	data[5] = (ccrc >> 8) & 0x00ff;
+
+	data[6] = 0;
+
+	for (i = 0; i < 7; i++)
+		csr[i] = 0;
+
+	for (i = 0; i < 7; i++)
+	{
+		unsigned int j;
+		data[i + 7] = 0;
+		for (j = 0; j <= 7; j++)
+		{
+			unsigned int b;
+			for (k = 6; k > 0; k--)
+				csr[k] = csr[k - 1];
+			csr[0] = (data[i] >> j) & 1u;
+			b = csr[0] + csr[2] + csr[5] + csr[6];
+			data[i + 7] |= (b & 1u) << j;
+		}
+	}
+
+	k = 0;
+	m = 0;
+	for (i = 0; i < 14; i++)
+	{
+		unsigned int j;
+		for (j = 0; j <= 7; j++)
+		{
+			lbits[k] = 1u & (data[i] >> j);
+			k += 16;
+			if (k > 111)
+				k = ++m;
+		}
+	}
+
+	k = 0;
+	for (i = 0; i < 14; i++)
+	{
+		int j;
+		data[i] = 0;
+		for (j = 7; j >= 0; j--)
+			if (lbits[k++])
+				data[i] |= 1u << j;
+	}
+
+	return &data[14];
+}
+
+const uint8_t header[] = {0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x07, 0x09, 0x2a, 0x44, 0x6f};
+
+int MDC1200_encode_single_packet(uint8_t *data, const uint8_t op, const uint8_t arg, const uint16_t unit_id)
+{
+	memcpy(data, header, sizeof(header));
+	data += sizeof(header);
+
+	data[0] = op;
+	data[1] = arg;
+	data[2] = (unit_id >> 8) & 0x00ff;
+	data[3] = (unit_id >> 0) & 0x00ff;
+
+	encode_data(data);
+
+	return 26;
+}
+
+int MDC1200_encode_double_packet(uint8_t *data, const uint8_t op, const uint8_t arg, const uint16_t unit_id, const uint8_t b0, const uint8_t b1, const uint8_t b2, const uint8_t b3)
+{
+	memcpy(data, header, sizeof(header));
+	data += sizeof(header);
+
+	data[0] = op;
+	data[1] = arg;
+	data[2] = (unit_id >> 8) & 0x00ff;
+	data[3] = (unit_id >> 0) & 0x00ff;
+
+	data = encode_data(data);
+
+	data[0] = b0;
+	data[1] = b1;
+	data[2] = b2;
+	data[3] = b3;
+
+	encode_data(data);
+
+	return 40;
+}
+/*
+void test(void)
+{
+	uint8_t data[14 + 14 + 5 + 7];
+
+	const int size = MDC1200_encode_single_packet(data, 0x12, 0x34, 0x5678);
+
+//	const int size = MDC1200_encode_double_packet(data, 0x55, 0x34, 0x5678, 0x0a, 0x0b, 0x0c, 0x0d);
+}
+*/