AIS3.Encoding payload of AIS

Idea is to use GPS information, to send out a AIS message.there are several items need to be built up:

1. messge type: plan to use type 1 for position report
1. which makes 6 bits 0b000001
2. repeat indicator: 0
1. which makes 2 bits 0b00
3. MMSI: 543543543
1. whcih maks 30 bits: 0b100000011001011101000011110111
4. Navigation status: 8 , under way sailing
1. which makes 4 bits: 0b1000
5. rate of turn: 128, not available
1. which makes 8 bits:0b01000000
6. SOG: 8.8kt
1. 8.8knt=88(unit at 0.1kt), which makes 0b0001011000
7. position accuracy: 0( GNSS >10m) or 1 (DGPS<10m)
1. which makes 0b0
8. Longitude 
1.   -149.329461 is presneted with unit = 1/0000min in 28bits, -149.329461degree*60000=-89597676.6, round to -89597677 
2. 89597677 in 28 bit=0b 0101 0101 0111 0010 0110 1110 1101
3. flip bits:1010 1010 1000 1101 1001 0001 0010
4. add 1=  1010101010001101100100010011 , this is -89597677 in 28 bits binary
9. Latitude
1. -17.732161 degrees in unit of 1/10000 min=-10,639,296.6 round to -10639296
2. 10639296 in 27 bits= 0b 000 1010 0010 0101 0111 1100 0000
3. flip bit: 0b111 0101 1101 1010 1000 0011 1111
4. add 1=  0b111010111011010100001000000
10. COG
1. 123.4 degree, in unit of 0.1 degree=1234
2. 1234 in 12 bits=0b0100 1101 0010
11. True heading 0 to 359 degrees, 511 = not available.
1. 511 in 9 bits=0b111111111
12. time stamp seconds
1. 30 second
2. 30 in 6bits=0b011110

For bit 143~167 no to use. so there is 25 bits I took the last 25 bits from previous example

0b0 000000 001000 011000 011011 

Which make the whole payload=
000001001000000110010111010000111101111000010000000001011000010101010100011011001000100111110101110110101000010000000100 1101 00101111111110111100000000001000011000011011 

Now, how to convert it into 6 bits??

well, I decided to use the most stupid one, one by one.....

Here I made a bit map to help me understand the correct mapping:

0	type	5	0
1		4
2		3
3		2
4		1
5		0
6	repeat	5	1
7		4
8	MMSI 29	3
9	28	2
10	27	1
11	26	0
12	25	5	2
13	24	4
14	23	3
15	22	2
16	21	1
17	20	0
18	19	5	3
19	18	4
20	17	3
21	16	2
22	15	1
23	14	0
24	13	5	4
25	12	4
26	11	3
27	10	2
28	9	1
29	8	0
30	7	5	5
31	6	4
32	5	3
33	4	2
34	3	1
35	2	0
36	1	5	6
37	0	4
38	status	3
39		2
40		1
41		0
42	turn 7	5	7
43	6	4
44	5	3
45	4	2
46	3	1
47	2	0
48	1	5	8
49	0	4
50	SOG 9	3
51	8	2
52	7	1
53	6	0
54	5	5	9
55	4	4
56	3	3
57	2	2
58	1	1
59	0	0
60	accuracy	5	10
61	Lon 27	4
62	26	3
63	25	2
64	24	1
65	23	0
66	22	5	11
67	21	4
68	20	3
69	19	2
70	18	1
71	17	0
72	16	5	12
73	15	4
74	14	3
75	13	2
76	12	1
77	11	0
78	10	5	13
79	9	4
80	8	3
81	7	2
82	6	1
83	5	0
84	4	5	14
85	3	4
86	2	3
87	1	2
88	0	1
89	lat 26	0
90	25	5	15
91	24	4
92	23	3
93	22	2
94	21	1
95	20	0
96	19	5	16
97	18	4
98	17	3
99	16	2
100	15	1
101	14	0
102	13	5	17
103	12	4
104	11	3
105	10	2
106	9	1
107	8	0
108	7	5	18
109	6	4
110	5	3
111	4	2
112	3	1
113	2	0
114	1	5	19
115	0	4
116	Course 11	3
117	10	2
118	9	1
119	8	0
120	7	5	20
121	6	4
122	5	3
123	4	2
124	3	1
125	2	0
126	1	5	21
127	0	4
128	Heading 8	3
129	7	2
130	6	1
131	5	0
132	4	5	22
133	3	4
134	2	3
135	1	2
136	0	1
137	second 5	0
138	4	5	23
139	3	4
140	2	3
141	1	2
142	0	1
143	Maneuver 1	0
144	0	5	24
145	spare 2	4
146	1	3
147	0	2
148	raim 0	1
149	sync state 1	0
150	0	5	25
151	slot time-out 2	4
152	1	3
153	0	2
154	hours         4	1
155	3	0
156	2	5	26
157	1	4
158	0	3
159	minutes      6	2
160	5	1
161	4	0
162	3	5	27
163	2	4
164	1	3
165	0	2
166	1	1
167	0	0

when :
sync state=0, UTC direct
When slot timeout = 1 - Then the sub message is UTC hour and minute
Hour (0-23) should be coded in bits 13 to 9

Minute (0-59) should be coded in bit 8 to 2

Here is the git
https://github.com/Ldsrc2008/AIS-encode-arduino