SLLA573 May   2022 THVD8000

 

  1.   Trademarks
  2. 1Introduction
  3. 2Tests and Setup
    1. 2.1 Test 1: 4-Node Star Network Test
    2. 2.2 Test 2: 4-Node Terminated Star Network Test
    3. 2.3 Test 3: 4-Node Loaded and Terminated Star Network Test
    4. 2.4 Test 4: 4-Node Loaded and Terminated Star Network Test with Line Driver
  4. 3Summary

2.2 Test 2: 4-Node Terminated Star Network Test

To make THVD8000 work for the 4-node star topology, the system is improved by terminating every node with a 120-Ω resistor like Figure 2-4.

Figure 2-4 4-Node Terminated Star Network

The termination resistance matches the cable’s characteristic impedance. Therefore, signal reflection is minimized and signal integrity is improved greatly, which is shown in the waveforms of Figure 2-5. The signal is measured at the same locations as in the last test – D of Node 1, bus pins and R of Node 3.

GUID-20220209-SS0I-KZF7-H9WV-HKBTKCGKJ08J-low.png Figure 2-5 Waveforms of 4-Node Terminated Star Network

With the 1-to-4 USB hub and TTL-232R cables mentioned previously installed, all data are checked in 4 GUI windows. In Figure 2-6, COM3 is Node 1 that transmits the data, while COM4, 5 and 6 are in the receive mode of Node 2, 3, and 4. With sending and receiving the string repeatedly, the communication is proven to be successful in this configuration. Then each node in the network is set to send data, while the rest nodes are checked for receiving data. By doing this, the quality of communication is verified for all the nodes.

GUID-20220209-SS0I-PFFH-JVZP-LXTJJMJFR98P-low.png Figure 2-6 GUI of 4-COM Ports of the 4-Node Terminated Star Network