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CH340 USB to TTL Serial Adaptor (HCMODU0076) 
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Joined: Sun Aug 05, 2012 4:02 pm
Posts: 682
Post CH340 USB to TTL Serial Adaptor (HCMODU0076)


The CH340 USB to serial adaptor (HCMODU0076) makes use of the CH340 USB to serial IC to provide a low cost alternative to our popular FTDI based module. Although much cheaper this module doesn't lack in features or usability. Once you have installed the drivers the module will appear as a normal serial COM port on your computer making it compatible with most terminal programs and development environments such as the Arduino IDE.

The module includes a small switch which allows the voltage available at the VC (Supply output) pin to be switched between 3.3 and 5V. Data pins include TX, RX, CTS and DTR (needed for automatic reset when programming Arduino boards). These digital pins are at 5V TTL levels allowing them to be directly interfaced most 5V microcontrollers.

Please note: Driver support is currently for Microsoft Windows 32/64 bit only.


DTR....Data Terminal Ready
RXD....Serial in
TXD....Serial out
VC......3.3V or 5V Supply out selected via switch
CTS.....Clear To Send


Windows drivers:


MAC installation instructions

New code signed version confirmed to work with 10.12 Sierra


Older code signed version confirmed to work with El Capitan



Download the driver (you must be logged in to download)

Once downloaded, double-click the zip file to unzip it.

Run installer found in that folder.

If asked to restart, do not restart just yet.

Now restart your Mac.

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Thu Feb 26, 2015 11:04 am

Joined: Wed Sep 09, 2015 2:36 pm
Posts: 2
Post Re: CH340 USB to TTL Serial Adaptor (HCMODU0076)
I bought 2 of these adapter recently and I discovered that I could not upload code to a breadboard Atmega 328P with one of them. (I only have one at the moment as the other was for a friend).

I had a useful phone discussion with Andrew yesterday at which time I thought the problem was that the adapter was failing to cause the Atmega 328 to reset when trying to upload code. On my adapter the DTR line is LOW by default and goes HIGH briefly when a program is to be uploaded. This seems to be the reverse of normal behaviour.

Later I came to the conclusion that the adapter was actually causing the 328 to reset and the problem was that it would not work properly at 57600 baud which is the upload rate used by the bootloader. The adapter works fine at 115200 baud and at 19200 baud.

After a lot of fiddling around I managed to compile a version of the Optiboot bootloader that uploads at 19200 baud and now I can upload with the CH340 as well as with an older USB-TTL cable that i have had for a few years and which works at 57600 baud.


Wed Nov 01, 2017 7:47 pm
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