Catalogue CRC Calculation Humidity Sensor
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SeNSIRION
SHTXX Application Note CRC -me sensor company
2.2 Bytewise
With this implementation the CRC data is stored in a 256 byte lookup table. Perform the following operations:
1. Initialize the CRC register with the value of the lower nibble of the value of the status register (reversed (sos^ss'oooo)). (default '00000000' = 0)
2. XOR each (transmitted and received) byte with the previous CRC value. The result is the new byte that you need to calculate the CRC value from.
3. Use this value as the index to the table to obtain the new CRC value.
4. Repeat from 2.) until you have passed all bytes through the process.
5. The last byte retrieved from the table is the final CRC value.
6. The CRC value retrieved from the SHTxx must be reversed (bit 0 = bit 7, bit 1=bit 6 ... bit 7 = bit 0) and can then be compared to the final CRC value.(2)
2.2.1 256 byte CRC Lookup table
0
1
2
3
4
J LO
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
0
49
98
83
196
245
166
151
185
136
219
234
125
76
31
46
67
114
33
16
135
182
229
212
250
203
152
169
62
15
92
109
32
33
34
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
134
183
228
213
66
115
32
17
63
14
93
108
251
202
153
168
197
244
167
150
1
48
99
82
124
77
30
47
184
137
218
235
64
~65
66
~67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
61
12
95
110
249
200
155
170
132
181
230
215
64
113
34
19
126
79
28
45
186
139
216
233
199
246
165
148
3
50
97
80
96
~97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
187
Ì38~
217
"232"
127
~78~"
29
~4T
2
~57
96
~87
198
"247
164
149"
248
"220T
154
77T
60
~13
94
ITT
65
712"
35
"18""
133
T80"
231
214
128
729
130
73T
132
733
134
735
136
737
138
739
140
Ì4T
142
T43
144
T45
146
T47
148
T49
150
T5T
152
T53
154
T55
156
T57
158
159
122
75
24
41
190
143
220
237
195
242
161
144
7
54
101
84
57
8
91
106
253
204
159
174
128
177
226
211
68
117
38
23
160
161
162
163
164
765
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
252
205
158
175
56
9
90
107
69
116
39
22
129
176
227
210
191
142
221
236
123
74
25
40
6
55
100
85
194
243
160
145
192
193
194
795
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
71
118
37
20
131
178
225
208
254
207
156
173
58
11
88
105
4
53
102
87
192
241
162
147
189
140
223
238
121
72
27
42
224
^25
226
^27
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
193
240
163
146
5
52
103
86
120
73
26
43
188
141
222
239
130
179
224
209
70
119
36
21
59
10
89
104
255
206
157
172
This is different to other CRC implementations
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