modbus_port_esp32

lib freemodbus porting for esp32

you must know thise lib should be used for modbus master role.

implemented:(see components/esp-modbus/functions/)

一、简述

FreeModbus是一款开源的Modbus协议栈，但是只有从机开源，主机源码是需要收费的。同时网上也没有发现比较好的开源的Modbus主机协议栈，所以才开发这款支持主机模式的FreeModbus协议栈。本版FreeModbus版本号更改为V1.6,支持Modbus主机协议栈，特性如下：

CMD - 0x01

eMBMasterReqReadCoils

CMD - 0x02

eMBMasterReqReadDiscreteInputs

CMD - 0x03

eMBMasterReqReadHoldingRegister

CMD - 0x04

eMBMasterReqReadInputRegister

CMD - 0x05

eMBMasterReqWriteCoil

CMD - 0x06

eMBMasterReqWriteHoldingRegister

CMD - 0x0f

eMBMasterReqWriteMultipleCoils

CMD - 0x10

eMBMasterReqWriteMultipleHoldingRegister

CMD - 0x17

eMBMasterReqReadWriteMultipleHoldingRegister

--now add rs485 support (note:this demo rs485 en pin using gpio12)--

thanks armink ! more reference seeing his git>https://github.com/armink/FreeModbus_Slave-Master-RTT-STM32