I used a simple FPC bread-board adapter to confirm that the pin-outs are correct but was far from convenient to use.
After some testing, I found that the module in its default state emulates a USB keyboard outputting the ASCII contents of the bar-code. The UART pins are completely unresponsive.
“BEEP_OUT” is actually outputting square-wave tones, adding a simple NPN transistor and speaker gives the familiar “Beep” when a bar-code is read.
The “LED_EN” pin is an output for an LED (Active high, 3v3). A LED with current limiting resistor is all that was required.
The “Trigger” pin as I suspected is for a button to trigger reading, simply pulling this low is all that was required.
After some help and encouragement from Peter at Village Vending I’ve discovered the module is manufactured by Guangzhou Yoko Electron Co., Ltd (Also known as Youku Electronics). They have several manuals on the website which looked like they might work so I built a more usable breakout board.
Sadly none of the manuals on the website have worked but they did have a technical contact email address on the webpage. After a quick email I received a reply from their Sales Manager with a copy of the manual which has all of the configuration barcodes needed. M4A E2000A EP2000A MK30 E3000H E3100H User Manual
I have now cleaned up the design and added a USB Type-B connector for convenience.