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https://github.com/zimbora/esp32-modbusrtu
library to communicate with external device using ModbusRTU protocol
https://github.com/zimbora/esp32-modbusrtu
Last synced: 2 days ago
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library to communicate with external device using ModbusRTU protocol
- Host: GitHub
- URL: https://github.com/zimbora/esp32-modbusrtu
- Owner: zimbora
- License: mit
- Created: 2022-10-28T14:16:18.000Z (about 2 years ago)
- Default Branch: main
- Last Pushed: 2023-11-04T19:08:23.000Z (about 1 year ago)
- Last Synced: 2024-04-29T22:42:05.604Z (7 months ago)
- Language: C++
- Size: 159 KB
- Stars: 1
- Watchers: 1
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: License.md
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README
# esp32-ModbusRTU
## BUGS
- !! this packet: 1,16,22,2 used with rs485_read makes program crash
## Description
package to read and write on modbus rtu slaves using a serial connection.
## Implementation
This library is prepared to receive a decoded packet, calculate crc-16, build the frame, send, wait for response
and return data received.
In case of error, the error can be obtained calling getLastError method.
[static uint8_t rs485_read(uint8_t unit_id, uint8_t fc, uint16_t address, uint16_t len, uint8_t* data, uint16_t* size)](#RS485-read)
[static uint8_t rs485_write(uint8_t unit_id, uint8_t fc, uint16_t address, uint16_t len, uint8_t* data, uint16_t* size)](#RS485-write)
[static String getLastError()](#Get-error)
## Examples
Run programs inside examples folder to check how it works
### demo
Request data from slave
## Unit Test with clang
>> chmod u+x make.sh
>> ./make.sh
If needed uncomment DEBUG FLAGS in Makefile
## TODO
Allow configurations for serial port
## Limitations
rs485_read method can only store MAX_VALUE_LEN bytes of retrieved payload (check modbus-rtu file to see macro value)
## Public Methods - Extension
### RS485 read
* @param unit_id - unit id
* @param fc - function code
* @param address
* @param len - number of registers to be read
* @param data - pointer to received payload
* @param size - maximum size of passed pointer, returns length of data read
* @return error - 0 in case of no error
```
static uint8_t rs485_read(uint8_t unit_id, uint8_t fc, uint16_t address, uint16_t len, uint8_t* data, uint16_t* size)
```
#### Example
```
uint16_t size = 32;
uint8_t* data = (uint8_t*)malloc(size);
if(data != nullptr){
uint8_t error = modbusrtu.rs485_read(1,3,0,2,data,&size);
}
free(data);
```
### RS485 write
* @param unit_id - unit id
* @param fc - function code
* @param address
* @param len - number of registers to be read
* @param data - pointer to payload to be written
* @param size - size of payload to be written
* @return error - 0 in case of no error
```
static uint8_t rs485_write(uint8_t unit_id, uint8_t fc, uint16_t address, uint16_t len, uint8_t* data, uint16_t* size)
```
#### Example
```
uint16_t size = 32;
uint8_t* data = (uint8_t*)malloc(size);
if(data != nullptr){
data[0] = 0x00;
data[1] = 0x00;
data[2] = 0x00;
data[3] = loop_counter++;
uint8_t error = modbusrtu.rs485_write(1,16,0,2,data,&size);
}
free(data);
```
### Get error
* @return error in string format
```
static String getLastError()
```
#### Example
```
String error_msg = modbusrtu.getLastError();
if(error_msg != "")
Serial.println("error msg: "+error_msg);
```