# DeviceBit DTU Tutorial 1: Overview Label: DTU modbus --- DTU (Data Transfer unit) is a kind of universal name, and in our later tutorials, DTU is a special name for the device whose one termimal is used as the server for TCP client, and the other terminal is used as the master for specific serial devices( such as TTL 232 485 etc.) It has the following two functions. - Link conversion for tcp2serial data - Send a registration sequence to the server after tcp connection Most of the existing DTU products can realize the above two funtions, and later our main content is divided into two parts 1. Use existing products to connect existing Modbus RTU devices to DeviceBit. 2. DIY low-cost or multi-purpose DTU (open source hardware) to connect the Modbus RTU devices to DeviceBit. Acturally, we can use code to illustrate the functions of DTU directly,[Illustrate the functions of DTU by python ][1] Talk about our understanding of with a simple diagram. ![先發一個DTU的框架圖][2] The following picture shows some of the equipment that we can use for DTU. ![我們手里的可以做DTU的部分設備的照片][3] The one in the first line is the industry DTU which can be bought directly on the market. This one is Ethernet uplink, as well as other different products which are WiFi, GPRS, or 4G uplink. Their usage is the same. The four things in the second line can be used in the DTU project implemented with Openwrt routers, which belongs to the open source project. It's advantage is to suppot multi-uplinks such as 4G, WiFi Ethernet with one device. The disadvantage is that the implementation code is still in iteration, and there may be bugs. The four things in the third line can be used in the DTU project implemented with a simpler bottom hardware, which belongs to the open source project using relatively hot scripts for development. Nodemcu luat has the advantage of being open source and cheap. The disadvantage is that it needs iteration to be stable gradually. ---------- 相關內容： [用python當DTU 把Modbus設備數據送到樂聯網教程][4] [MODBUS 電表接入樂聯網教程][5] [1]: https://github.com/lewei50/python/blob/master/lewei_tcp2serial.py [2]: http://doc-resources.lewei50.com/lewei50/img/DTU-laoliu-20170512-1.jpg [3]: http://doc-resources.lewei50.com/lewei50/img/DTU-laoliu-20170512-2.jpg [4]: http://www.jianshu.com/p/dea70ea26847 [5]: http://www.jianshu.com/p/3a1332c8f703