Fused USB to UART adapter

This is yet another USB to UART adapter, or is it? The 2nd revision of my previous USB to UART adapter, it is better than ever.

What's new in M180v3

• The missing pin indicator silkscreen is added.
• The AMS1117-3.3 regulator is removed after experiments revealed a way to make the internal regulator inside CH340G stable.
• Added a power indicating LED per Yuxi Liu's suggestion. Thanks, pal!
• USB Type A plug instead of USB Type B socket for USB interface.

Highlights

• USB to UART adapter with SparkFun FTDI compatible pinout, drop-in replacement of your SparkFun modules.
• CH340G chipset, plug and play on Windows 7+, OS X and Linux, and immune to either FTDIgate or Prolific fake chip ban.
• 500mA polyfuse on the USB power line, no more catastrophic "oops" moments.
• Through-hole USB Type A plug, almost impossible to break off.
• The PCB is as wide as a standard USB Type A plug, will not obscure each other or other standard plugs.
• Pads for adding a series capacitor (0805-size) to the DTR line for your Arduino-on-breadboard projects.

Story of creation

This project is created out of my own necessity: I had a few dodgy FT232RL and PL2303-based USB to UART modules, and the recent Prolific driver update and FTDIgate killed them. However the one of my friends' MCS-51 development board did not suffer from this plague of drivers disabling devices, and it is based on this CH340G chipset.

I bought a few of those CH340G chips (which are an order of magnitude or two cheaper than both FT232RL and PL2303 by the way) and initial breadboard testing was a great success, with one problem: the internal 3.3V regulator is a little bit problematic. This issue is tamed in the otherwise ill-fated M180v2 PCB so this M180v3 inherited this part of the circuit.

I did have one mishap with the breadboard though: I was being a fool and connected a chip in reverse, shorting out the power rails on the USB port. The short circuit current draw immediately upset my MacBook's USB port and caused it to be shut down. (Thanks Apple for the superior protection circuitry, should this happened while it is connected to my years-old Lenovo desktop it will definitely let the magic smoke out of my chip and probably take out the computer's motherboard too) I decided to make sure whenever USB power is used on my further projects it is definitely fused.

During this test while minding other projects, I snapped the Micro-USB jack on my Arduino Leonardo clone, took the traces with it and damaged the board beyond repair. A sad me had to take out my hot air gun and disassemble the Leonardo just to recover the parts, and swear not to use those easily damaged jacks on my projects ever, especially those jacks that will subject to lots of wear and tear like USB.

Here comes my design, a USB to UART adapter based on the CH340G chipset, with the same SparkFun pinout, an extra-durable through-hole USB Type A plug, and a fused power rail.

Where is M180v2?

There exists a M180v2 revision after the original M180 sold out, but it was ultimately scrapped.

The M180v2 PCB have all the features this M180v3 have, but instead of a through hole USB Type A plug soldered onto the PCB, a Type A plug was designed directly onto the PCB - that is, a card edge connector that should mate with a USB Type A socket - but this design was not reliable - not even with any kind of help I can think of.

Hacks

You can hack this board for your own purposes!

• On the bottom of the board, I have provided a 0805-sized pad for a series capacitor if you are building an Arduino-on-breadboard project. Just cut the trace between the pads and solder your capacitor there and you are good to go.
• The 3.3V modification is no longer possible, since I removed the regulator. If you need a 3.3V version, please tell me.

About me

I am Max, a college student major in computer engineering and dabbles in electronics engineering. This is one of my just-for-fun spare time projects.

This board is hand assembled by myself. Made in Shanghai with love, it will not be your one-hang-low Shenzhen crap.