Data Sheet

The Data Sheet of CH340 (the first) 8
7
.3 USB to RS232 Converter Configuration (Simplified version using R232)
Th
e image above is USB to RS232 converter design
too, the function of this circuit is the same with 7.2 section
except the range of output RS232 is narrower. When R232 pin is driven high, the assistant
RS232 function will be
enabled, just need to add some diodes, transistors, resistor
s and capacitors, the special level conversion chip U5 in
section 7.2 could be replaced and the hardware cost is lower.
7.4 USB to Infrared Adapter
The image above is USB to infrared adapter design is composed with USB convert I
rDA infrared chip
CH340R and infrared transceiver U14 (ZHX1810/HSDL3000 etc).The resistor R13 is used to weaken
influence of
large current in infrared transmitting. The current limiting resistor R14 should be adjusted according to the
manufacturer’s recommended value of the infrared tran
sceiver U14.
7.5. USB to RS485 Converter Configuration
Th
e TNOW pin can be used to control DE (high active send enable) and RE# (low active receive enable)
pin of RS485 transceiver.