Several methods to control LEGO Code Pilot and MicroScout with VLL
The LEGO Code Pilot was the first LEGO pBrick (programmable brick), the first member of the MINDSTORMS familly.
It could receive and store "instructions" through a optical input. The set came with a laminated A3 paper, the "Code Pilot Bar Code Sheet" containing code bars of the available instructions. A later set, the Scout, could also send these instructions by flashing a LED. Another pBrick, the MicroScout, could also receive these instructions. A common method to connect the Scout to the MicroScout was through an optic fiber link.
The RCX SDK included the details of the VLL language and it was possible to use the RCX output with a lamp to generate VLL codes.
Since the EV3 can also control a light, I decided to use it to control the Code Pilot and the MicroScout. After first success I tryed other methods.
1. EV3 output port with NXT-RCX adapter and Power Functions Light
In ev3dev configure the output port to led mode and use the 'vll-outa.py' script
2. EV3 status LED
This is merely a curiousity since its totally unpractical but nevertheless it was a nice find: the EV3 status LEDs generate enough bright to control a MicroScout if you use a TOSlink fiber optic cable (unfortunately the 21L LEGO optic fiber isn't usable, perhaps a smaller LEGO fiber optic can work?)
In ev3dev just run the 'vll-ev3led.py' script, it sends VLL commands through the LEFT LED.
3. USB FTDI adapter in bitbang mode and a LED (works with ev3dev, linux laptop and Raspberry Pi, probably also with Windows and OSX)
Get an USB FTDI adapter like the Sparkfun FT232R Breakout Board and connect a LED and a resistor between GND and TXD, then use the 'vllftdi.py' script. You need to cread a udev rule or run your script as root / with sudo.
Still to document:
Arduino (NodeMCU) and a LED connected to a GPIO pin
Raspberry Pi and a LED conencted to a GPIO pin
'vll-atat-py' is a python script to control a MicroScout with the EV3 LEFT/RIGT/UP buttons. Here a video showing it controlling an AT-AT from the 9754 Dark Side Devoloper Kit: https://youtu.be/tdrDTqwzdbI
Kevin Walters wrote an excellent tutorial on Adafruit site on using a Feather M0 Bluefruit LE to control a MicroScout droid: https://learn.adafruit.com/bluetooth-remote-for-lego-droid
An interesting discovery: although the LEGO optical fiber (~21L length) barelly works, a TOSLink optical fiber (1.2 meters or 4 feet) works fine, allowing better distances. And it connects very well to LEGO bricks.