USB to serial port+RS485 module

2022.10.24, initial construction:
In order to solve the problem of insufficient serial port, 485 and other assistants during debugging, and occupying too many computer USB ports, a self-made USB to TTL&cRS485 module is built. This module has two channels of TTL and one channel of 485, and one channel is reserved. USB_SLAVE can realize multi-module cascading. It can expand multiple COM ports while only occupying one USB port on the computer. The key is small and compact:
the circuit of the module is relatively simple. I also made the board and used it for three months to meet the expected needs. However, There are a few points to note: 1. TTL and 485 transceiver LED lights will always be on...and the current limiting resistors of the TTL Tx and RX LEDs must be above 10k, otherwise they will be too bright...( V0.2 version has solved)
3. There will be a byte echo when sending data through RS485... I don’t know if the 120 ohm is not matched properly.
4. No welding is needed here, CH340E comes with 485 transceiver control (deleted in V0.2 version) This circuit)
 
 
2022.11.27, updated the V0.2 version to solve the problem of the serial port TxRx light being always on:
Latest proofing:
 
 
 
 
2023.02.10, updated the V2.0 version:
CH344 and CH348 were discovered, directly supporting 4 and 8-way serial ports, And each channel is equipped with TNOWx (can be used for RS485 transceiver control). Compared with the previous hub+ch340 combination, the number of materials is saved and the PCB can be smaller.