ModBus协议简介及移植到STM32单片机
https://blog.csdn.net/silent123go/article/details/92440091

Modbus测试工具ModbusPoll与Modbus Slave使用方法
https://blog.csdn.net/byxdaz/article/details/77979114

modbus slave工具
http://www.cr173.com/soft/21410.html

modbus poll工具
http://www.cr173.com/soft/21405.html