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Wiki source code of 08 Communication

Version 4.8 by Stone Wu on 2022/07/07 15:18
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Leo Wei 1.1 1 The VD2 series servo drive has Modbus communication function, which could cooperate with the host computer for parameter modification, parameter query, monitoring volume servo status query and control. The servo drive is used as a slave device.
2
3 = **Modbus communication** =
4
5 == **Hardware wiring** ==
6
7 The position of RS485 communication port (take VD2B as an example) is as the figure below.
8
Joey 1.2 9 (% style="text-align:center" %)
10 [[image:image-20220608154248-1.png]]
Leo Wei 1.1 11
12 Figure 8-1 The position of RS485 communication port of VD2B drive
13
Joey 3.1 14 For the position of the RS485 communication port of other models, see __[[4.5 Communication signal wiring>>https://docs.we-con.com.cn/bin/view/Servo/2.%20User%20Manual/06%20VD2%20SA%20Series%20Servo%20Drives%20Manual%20%28Full%20V1.1%29/04%20Wiring/#HCommunicationsignalwiring]]__.
Leo Wei 1.1 15
16 The servo drive adopts RS485 half-duplex communication mode. The 485 bus should adopt the hand-in-hand structure instead of the star structure or the bifurcated structure. The star structure or bifurcation structure will produce reflected signals, which will affect the 485 communication.
17
18 (% class="table-bordered" %)
Joey 2.1 19 |(% style="text-align:center; vertical-align:middle" %)[[image:image-20220611153134-1.png]]
Leo Wei 1.1 20 |(((
21 ✎The wiring must use shielded twisted pair, stay away from strong electricity, do not run in parallel with the power line, let alone bundle it together!
22
23 ✎In a half-duplex connection, only one servo drive can communicate with the host computer at the same time. If two or more servo drives upload data at the same time, bus competition will occur. Not only will it lead to communication failure, it may also cause some components to generate large currents and damage the components.
24 )))
25
Joey 1.2 26 (% style="text-align:center" %)
Joey 1.3 27 [[image:image-20220608174415-1.png]]
Leo Wei 1.1 28
29 Figure 8-2 RS485 communication network wiring diagram
30
31 The terminal of RS485 network should use a terminating resistors of 120Ω to weaken the reflection of the signal. Intermediate networks cannot use terminating resistors.
32
33 No point in the RS485 network can be directly grounded. All devices in the network must be well grounded through their own grounding terminals.
34
35 (% class="table-bordered" %)
Joey 2.1 36 |(% style="text-align:center; vertical-align:middle" %)[[image:image-20220611153144-2.png]]
Leo Wei 1.1 37 |Under no circumstances can the grounding wire form a closed loop.
38
39 When wiring, consider the drive capability of the computer/PLC and the distance between the computer/PLC and the servo drive. If the drive capacity is insufficient, a repeater is needed.
40
41 = **Modbus communication protocol analysis** =
42
43 == **Modbus data frame format** ==
44
45 The VD2 series servo drives currently support the RTU communication format. The typical data frame format is shown in the table.
46
47 (% class="table-bordered" %)
48 |(% rowspan="2" style="text-align:center; vertical-align:middle; width:425px" %)**There should be a message interval not less than 3.5 characters at the beginning**|(% style="text-align:center; vertical-align:middle; width:166px" %)**Address**|(% style="text-align:center; vertical-align:middle; width:189px" %)**Function code**|(% style="text-align:center; vertical-align:middle; width:155px" %)**Data**|(% style="text-align:center; vertical-align:middle; width:158px" %)**CRC check code**
49 |(% style="text-align:center; vertical-align:middle; width:166px" %)1 byte|(% style="text-align:center; vertical-align:middle; width:189px" %)1 byte|(% style="text-align:center; vertical-align:middle; width:155px" %)N bytes|(% style="text-align:center; vertical-align:middle; width:158px" %)2 bytes
50
51 == **Description of supported function codes** ==
52
53 The host reads and writes data to the servo through Modbus RTU format (03, 06 function codes). The corresponding Modbus function codes are as follows:
54
55 (% class="table-bordered" %)
56 |(% style="text-align:center; vertical-align:middle" %)**Operate**|(% style="text-align:center; vertical-align:middle" %)**Command code**
Stone Wu 4.7 57 |(% style="text-align:center; vertical-align:middle" %)Read 16-bit/32-bit function code|(% style="text-align:center; vertical-align:middle" %)0x03
Leo Wei 1.1 58 |(% style="text-align:center; vertical-align:middle" %)Write 16-bit function code|(% style="text-align:center; vertical-align:middle" %)0x06
Stone Wu 4.7 59 |(% style="text-align:center; vertical-align:middle" %)Write 32-bit function code|(% style="text-align:center; vertical-align:middle" %)0x10
Leo Wei 1.1 60
Stone Wu 4.7 61 **Read function code: 0x03**
Leo Wei 1.1 62
63 Request format:
64
Stone Wu 4.7 65 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)**Initial address**|(% colspan="2" %)**Number of reads**|(% rowspan="2" %)**CRC check code**
66 |**high byte**|**low byte**|**high byte**|**low byte**
67 |1 byte|03|1 byte|1 byte|1 byte|1 byte|2 bytes
Leo Wei 1.1 68
69 Correct response format:
70
Stone Wu 4.7 71 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% rowspan="2" %)**Number of bytes of returned data**|(% colspan="2" %)**Register 1**|(% rowspan="2" %)**…**|(% rowspan="2" %)**CRC check code**
72 |**high byte**|**low byte**
73 |1 byte|03|1 byte|1 byte|1 byte|…|2 bytes
Leo Wei 1.1 74
Stone Wu 4.7 75 **Write function code: 0x06**
Leo Wei 1.1 76
77 Request format:
78
Stone Wu 4.8 79 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)(((
80 **Register address**
81 )))|(% colspan="2" %)**Data**|(% rowspan="2" %)**CRC check code**
Stone Wu 4.7 82 |**high byte**|**low byte**|**high byte**|**low byte**
83 |1 byte|06|1 byte|1 byte|1 byte|1 byte|2 bytes
Leo Wei 1.1 84
85 Response format:
86
Stone Wu 4.8 87 |(% rowspan="2" %)**Address**|(% rowspan="2" %)**Function code**|(% colspan="2" %)**Register address**|(% colspan="2" %)**Data**|(% rowspan="2" %)**CRC check code**
Stone Wu 4.7 88 |**high byte**|**low byte**|**high byte**|**low byte**
89 |1 byte|06|1 byte|1 byte|1 byte|1 byte|2 bytes
Leo Wei 1.1 90
91 If the setting is successful, the original is returned
92
Stone Wu 4.7 93 |(% rowspan="2" %)**There should be a message interval not less than 3.5 characters at the beginning**|**Address**|**Function code**|**Data**|**CRC check code**
94 |1 byte|1 byte|N bytes|2 bytes
Leo Wei 1.1 95
Stone Wu 4.7 96 (% style="color:inherit; font-family:inherit; font-size:26px" %)**CRC check**
Leo Wei 1.1 97
98 The servo uses a 16-bit CRC check, and the host computer must also use the same check rule, otherwise the CRC check will make mistake. When transmitting, the low bit is in the front and the high bit is at the back. The CRC code are as follows:
99
100 {{code language="LUA"}}
101 {
102
103     Uint16 crc = 0xffff;
104
105     Uint16 i;
106
107
108
109   while(uLen--)
110
111   {
112
113     crc ^=(Uint16) *pBuf++;
114
115     for(i=0; i<8; i++)
116
117     {
118
119       if(crc & 0x0001)
120
121 {
122
123 crc = (crc >> 1) ^ 0xa001;
124
125 }
126
127 else
128
129 {
130
131 crc = crc >> 1;
132
133 }
134
135
136
137     }
138
139   }
140
141   return crc;
142
143 }
144
145 return crc;
146
147 }
148 {{/code}}
149
150 == **Error response frame** ==
151
152 (% class="table-bordered" %)
153 |(% style="text-align:center; vertical-align:middle" %)**Address**|(% style="text-align:center; vertical-align:middle" %)**Function code**|(% style="text-align:center; vertical-align:middle" %)**Error code**|(% style="text-align:center; vertical-align:middle" %)**CRC check code**
154 |(% style="text-align:center; vertical-align:middle" %)1 byte|(% style="text-align:center; vertical-align:middle" %)Command code+0x80|(% style="text-align:center; vertical-align:middle" %)Error code|(% style="text-align:center; vertical-align:middle" %)2 bytes
155
156 When an error occurs, set the function code bit7 issued by the host to 1, and return (for example, 0x03 returns 0x83, 0x06 returns 0x86); the description of the error code are as follows.
157
158 (% class="table-bordered" %)
159 |(% style="text-align:center; vertical-align:middle" %)**Error code**|(% style="text-align:center; vertical-align:middle" %)**Coding description**
160 |(% style="text-align:center; vertical-align:middle" %)0x0001|(% style="text-align:center; vertical-align:middle" %)Illegal command code
161 |(% style="text-align:center; vertical-align:middle" %)0x0002|(% style="text-align:center; vertical-align:middle" %)Illegal data address
162 |(% style="text-align:center; vertical-align:middle" %)0x0003|(% style="text-align:center; vertical-align:middle" %)Illegal data
163 |(% style="text-align:center; vertical-align:middle" %)0x0004|(% style="text-align:center; vertical-align:middle" %)Slave device failure
164
165 == **Communication example** ==
166
167 **03 Function Code Read**
168
169 Read the monitoring volume U0-31 bus voltage, the Modbus register address corresponding to this variable is 7716 (0x1E24)
170
171 Request format:
172
173 (% class="table-bordered" %)
174 |(% style="text-align:center; vertical-align:middle" %)**Address**|(% style="text-align:center; vertical-align:middle" %)**Function code**|(% style="text-align:center; vertical-align:middle" %)**Register address high byte**|(% style="text-align:center; vertical-align:middle" %)**Register address low byte**|(% style="text-align:center; vertical-align:middle" %)**Data high byte**|(% style="text-align:center; vertical-align:middle" %)**Data low byte**|(% style="text-align:center; vertical-align:middle" %)**CRC check code**
175 |(% style="text-align:center; vertical-align:middle" %)1 byte|(% style="text-align:center; vertical-align:middle" %)06|(% style="text-align:center; vertical-align:middle" %)1 byte|(% style="text-align:center; vertical-align:middle" %)1 byte|(% style="text-align:center; vertical-align:middle" %)1 byte|(% style="text-align:center; vertical-align:middle" %)1 byte|(% style="text-align:center; vertical-align:middle" %)2 bytes
176
177 The slave responds normally:
178
179 (% class="table-bordered" %)
180 |(% style="text-align:center; vertical-align:middle" %)**Address**|(% style="text-align:center; vertical-align:middle" %)**Function code**|(% style="text-align:center; vertical-align:middle" %)**Number of bytes**|(% style="text-align:center; vertical-align:middle" %)**Data high byte**|(% style="text-align:center; vertical-align:middle" %)**Data low byte**|(% style="text-align:center; vertical-align:middle" %)**CRC low byte**|(% style="text-align:center; vertical-align:middle" %)**CRC high byte**
181 |(% style="text-align:center; vertical-align:middle" %)01|(% style="text-align:center; vertical-align:middle" %)03|(% style="text-align:center; vertical-align:middle" %)02|(% style="text-align:center; vertical-align:middle" %)0C|(% style="text-align:center; vertical-align:middle" %)26|(% style="text-align:center; vertical-align:middle" %)3C|(% style="text-align:center; vertical-align:middle" %)9E
182
183 The value read is 0x0C26, which means that the voltage is 311.0V.　
184
185 **06 Function Code Write**
186
187 P1-10 the maximum speed threshold is set to 3000rpm. This variable corresponds to the Modbus address: 266 (0x010A)
188
189 Request format:
190
191 (% class="table-bordered" %)
192 |(% style="text-align:center; vertical-align:middle" %)**Address**|(% style="text-align:center; vertical-align:middle" %)**Function code**|(% style="text-align:center; vertical-align:middle" %)**Register address high byte**|(% style="text-align:center; vertical-align:middle" %)**Register address low byte**|(% style="text-align:center; vertical-align:middle" %)**Data high byte**|(% style="text-align:center; vertical-align:middle" %)**Data low byte**|(% style="text-align:center; vertical-align:middle" %)**CRC low byte**
193 |(% style="text-align:center; vertical-align:middle" %)01|(% style="text-align:center; vertical-align:middle" %)06|(% style="text-align:center; vertical-align:middle" %)01|(% style="text-align:center; vertical-align:middle" %)0A|(% style="text-align:center; vertical-align:middle" %)0B|(% style="text-align:center; vertical-align:middle" %)B8|(% style="text-align:center; vertical-align:middle" %)AF
194
195 The slave responds normally:
196
197 |(% style="text-align:center; vertical-align:middle" %)**Address**|(% style="text-align:center; vertical-align:middle" %)**Function code**|(% style="text-align:center; vertical-align:middle" %)**Register address high byte**|(% style="text-align:center; vertical-align:middle" %)**Register address low byte**|(% style="text-align:center; vertical-align:middle" %)**Data high byte**|(% style="text-align:center; vertical-align:middle" %)**Data low byte**|(% style="text-align:center; vertical-align:middle" %)**CRC low byte**
198 |(% style="text-align:center; vertical-align:middle" %)01|(% style="text-align:center; vertical-align:middle" %)06|(% style="text-align:center; vertical-align:middle" %)01|(% style="text-align:center; vertical-align:middle" %)0A|(% style="text-align:center; vertical-align:middle" %)0B|(% style="text-align:center; vertical-align:middle" %)B8|(% style="text-align:center; vertical-align:middle" %)AF
199
200 = **Servo communication parameter setting** =
201
Joey 1.2 202 (% style="text-align:center" %)
Joey 1.3 203 [[image:image-20220608174504-2.png]]
Leo Wei 1.1 204
205 Figure 8-3 Modbus communication parameter setting process
206
207 **(1) Set the servo address P12-1**
208
209 When multiple servos are in network communication, each servo can only have a unique address, otherwise it will cause abnormal communication and fail to communicate.
210
211 **(2) Set the serial port baud rate P12-2**
212
213 The communication rate of the servo and the communication rate of the host computer must be set consistently, otherwise the communication cannot be carried out.
214
215 **(3) Set the serial port data format P12-3**
216
217 The data bit check methods of servo communication are:
218
219 Odd parity
220
221 Even parity
222
223 No parity
224
225 The stop bit: 1 stop bit and 2 stop bits.
226
227 The data frame format of the servo and the host computer must be consistent, otherwise the communication cannot be carried out.
228
229 **(4) Set that whether the function code changed by Modbus communication is written into EEPROM in real time [P12-4]**
230
231 When the host computer modifies the servo function code through communication, it can choose to store it in EEPROM in real time, which has the function of power-off storage.
232
233 If the value of the function code only needs to be rewritten once, and the value is used later, the function of real-time writing of the function code to EEPROM can be enabled.
234
235 If you need to change the value of the function code frequently, it is recommended to turn off the function of real-time writing to EERPOM of function code, otherwise the EEPROM will be shortened due to frequent erasing and writing of the EEPROM.
236
237 (% class="table-bordered" %)
Joey 2.1 238 |(% style="text-align:center; vertical-align:middle" %)[[image:image-20220611153214-3.png]]
Leo Wei 1.1 239 |After the EEPROM is damaged, the servo will have an non resettable fault!
240
241 **(5) Set the high and low order of the 32-bit monitoring data**
242
243 Part of the monitoring volume is 32-bit length and occupies 2 consecutive bias numbers. The user needs to set the order of the data high bit and low bit correctly, otherwise it will cause data reading and writing errors!
244
245 For example, U0-54 (position within 1 circle of absolute encoder) occupies two consecutive offset numbers, which are 0x1E3D and 0x1E3E respectively. Assuming the value of U0-54 is 0x12345678, the correct data sequence bit should be 0x1E3D=0x5678 , 0x1E3E=0x1234 (little endian mode: low byte first, high byte behind.)
246
247 The description of related function codes are as follows.
248
249 (% class="table-bordered" %)
Joey 2.1 250 |(% style="text-align:center; vertical-align:middle; width:121px" %)**Function code**|(% style="text-align:center; vertical-align:middle; width:205px" %)**Name**|(% style="text-align:center; vertical-align:middle; width:187px" %)(((
Leo Wei 1.1 251 **Setting method**
Joey 2.1 252 )))|(% style="text-align:center; vertical-align:middle; width:186px" %)(((
Leo Wei 1.1 253 **Effective time**
Joey 2.1 254 )))|(% style="text-align:center; vertical-align:middle; width:130px" %)**Default value**|(% style="text-align:center; vertical-align:middle; width:132px" %)**Range**|(% style="text-align:center; vertical-align:middle; width:335px" %)**Definition**|(% style="text-align:center; vertical-align:middle; width:189px" %)**Unit**
255 |(% style="text-align:center; vertical-align:middle; width:121px" %)P12-02|(% style="text-align:center; vertical-align:middle; width:205px" %)Baud rate|(% style="text-align:center; vertical-align:middle; width:187px" %)(((
Leo Wei 1.1 256 Operation setting
Joey 2.1 257 )))|(% style="text-align:center; vertical-align:middle; width:186px" %)(((
Leo Wei 1.1 258 Effective immediately
Joey 2.1 259 )))|(% style="text-align:center; vertical-align:middle; width:130px" %)2|(% style="text-align:center; vertical-align:middle; width:132px" %)0 to 5|(% style="width:335px" %)(((
Leo Wei 1.1 260 0-2400bps
261
262 1-4800bps
263
264 2-9600bps
265
266 3-19200bps
267
268 4-38400bps
269
270 5-57600bp
Joey 2.1 271 )))|(% style="text-align:center; vertical-align:middle; width:189px" %)-
272 |(% style="text-align:center; vertical-align:middle; width:121px" %)P12-03|(% style="text-align:center; vertical-align:middle; width:205px" %)Serial data format|(% style="text-align:center; vertical-align:middle; width:187px" %)(((
Leo Wei 1.1 273 Operation setting
Joey 2.1 274 )))|(% style="text-align:center; vertical-align:middle; width:186px" %)(((
Leo Wei 1.1 275 Effective immediately
Joey 2.1 276 )))|(% style="text-align:center; vertical-align:middle; width:130px" %)0|(% style="text-align:center; vertical-align:middle; width:132px" %)0 to 3|(% style="width:335px" %)(((
Leo Wei 1.1 277 0: 1 stop bit, no parity
278
279 1: 1 stop bit, odd parity
280
281 2: 1 stop bit, even parity
282
283 3: 2 stop bits, no parity
Joey 2.1 284 )))|(% style="text-align:center; vertical-align:middle; width:189px" %)-
285 |(% style="text-align:center; vertical-align:middle; width:121px" %)P12-04|(% style="text-align:center; vertical-align:middle; width:205px" %)Modbus communication data is written into EEPROM|(% style="text-align:center; vertical-align:middle; width:187px" %)(((
Leo Wei 1.1 286 Operation setting
Joey 2.1 287 )))|(% style="text-align:center; vertical-align:middle; width:186px" %)(((
Leo Wei 1.1 288 Effective immediately
Joey 2.1 289 )))|(% style="text-align:center; vertical-align:middle; width:130px" %)0|(% style="text-align:center; vertical-align:middle; width:132px" %)0 to 1|(% style="width:335px" %)(((
Leo Wei 1.1 290 0: Do not write to EEPROM, and do not store after power failure;
291
292 1: Write to EEPROM, power-down storage.
Joey 2.1 293 )))|(% style="text-align:center; vertical-align:middle; width:189px" %)-
Leo Wei 1.1 294
295 = **Modbus communication variable address and value** =
296
297 == **Variable address description** ==
298
299 Modbus registers are divided into two categories:
300
301 ~1. The first category is servo function code parameters (address: 0x0001 to 0x0D08), this part of the register is readable and writable (that is, 0x03 and 0x06 are supported);
302
303 2. The second category is the monitoring volume of the servo (address: 0x1E01 to 0x2010), this part of the register is only readable (0x03 function is supported).
304
305 **Servo function code representation: PXX-YY.**
306
307 XX: represents the function code group number,
308
309 YY: represents the bias within the function code group;;
310
311 During servo communication, the communication address of the function code is a 16-bit address, which is composed of the function code group number (high 8 bits) + group bias (low 8 bits), for example, the Modbus address corresponding to P12-1 (servo address) is 0x0C01.
312
313 **Servo monitor volume representation: Uxx-yy.**
314
315 xx: represents the monitoring volume group number,
316
317 yy: represents the bias within the monitoring volume group;
318
319 During Modbus communication, the starting address of the monitoring volume is 0x1E01, and the conversion relationship of the address is similar to the representation way of the function code.
320
321 For example, U0-01 (servo status) corresponds to the Modbus address is 0x1E01.
322
323 In order to facilitate actual use, this manual provides both decimal and hexadecimal address identification, it is shown in the following table:
324
325 (% class="table-bordered" %)
326 |(% style="text-align:center; vertical-align:middle" %)**Function code**|(% style="text-align:center; vertical-align:middle" %)(((
327 **Modbus address**
328
329 **(Hexadecimal)**
330 )))|(% style="text-align:center; vertical-align:middle" %)(((
331 **Modbus address**
332
333 **(Decimal)**
334 )))|(% style="text-align:center; vertical-align:middle" %)**Category**|(% style="text-align:center; vertical-align:middle" %)**Name**
335 |(% style="text-align:center; vertical-align:middle" %)P0-1|(% style="text-align:center; vertical-align:middle" %)0x0001|(% style="text-align:center; vertical-align:middle" %)1|(% style="text-align:center; vertical-align:middle" %)Basic settings|(% style="text-align:center; vertical-align:middle" %)Control mode
336
Joey 3.1 337 For detailed parameter addresses, please refer to __[["11.1 Lists of parameters".>>https://docs.we-con.com.cn/bin/view/Servo/2.%20User%20Manual/06%20VD2%20SA%20Series%20Servo%20Drives%20Manual%20%28Full%20V1.1%29/11%20Appendix/#HListsofparameters]]__
Leo Wei 1.1 338
339 == **Variable value type description** ==
340
341 When writing function codes with signed numbers, you need to convert the pre-written data into hexadecimal complements. The conversion rules are as follows:
342
343 ~1. The data is positive or 0: complement code = original code
344
345 2. The data is negative: complement code = 0xFFFF-absolute value of data + 0x0001
346
347 For example,The 16-bit signed positive number +100, the original code is 0x0064, and the complement is: 0x0064. The 16-bit signed positive number -100, its hexadecimal complement is: 0xFFFF-0x0064 + 0x0001 = 0xFF9C.
348
349 If it is an unsigned number, just pass it directly according to its original code. For example, if the decimal number is 32768, write 0x8000 directly.
350
351 == **Numerical unit description** ==
352
353 Some values have units and decimals, such as 0.1%, 0.1Hz, 0.01ms, and the corresponding value conversion is required when reading and writing. The methods are as follows:
354
355 ~1. When the unit is 0.1%: 1 represents 0.1%, 10 represents 1.0%, 1000 represents 100.0%. Therefore, writing 1000 means setting to 100.0%; on the contrary, if it is reading 1000, it means that the value is 100.0%;
356
357 2. When the unit is 0.01ms: 1 means 0.01ms, 50 means 0.5ms, 10000 means 100ms. Therefore, writing 1000 means setting to 10.00ms; on the contrary, if 1000 is read, it means 10.00ms; The other units can be deduced by this, and integer remains unchanged.