Now Updated for Arduino 1.6.6 November 2015 !
What is MRETV ?
MRETV is a few very simple circuits and a simple to use software interface that allows an Arduino to generate Video and Stereo Sound in the background while your sketch executes as normal. Your Arduino plugs directly into the A/V inputs of your TV, VCR, or projector. MRETV also has built in support for other peripherals like keyboards and mice.
Which Arduino's does MRETV work with?
MRETV has been tested and works with Arduino boards using 168, 328, and 2560 CPU's. With the Mega 2560 software serial Tx has a small hardware limitation.
Who can build MRETV?
Any Arduino user. Even if you have never built hardware before, the audio and video circuits are so simple they make a perfect first project. People with moderate experience can build them in about 5 minutes, and probably already have the parts.
How easy is it to program with MRETV?
You can set a string, make 1 function call, and the string shows on your TV. Changing the contents of the string changes the text showing on your TV (in real time without calling any function.)
Why use MRETV ?
An Arduino user interface often involves a few buttons or switches. Indicators commonly range from LEDs to 80 character displays. These can be a large part of the time and cost in a build. MRETV replaces these with a screen of 1 to over 1000 characters, stereo sound and a full PC keyboard. It can be built quickly and cheaply using only 6 resistors 2 diodes and 2 capacitors in total for all 3 circuits (video / stereo audio / keyboard).
What resources does MRETV use ?
The smallest footprint is about a 1.5k sketch using about 35 bytes of RAM, including interrupt stack use, plus 1 byte of RAM for each character location on screen (1 or more locations). The screen character space can be dual purposed. Video uses an 8 bit timer and two IO pins. Audio uses an 8 bit timer and two IO pins. The software serial Tx stream is provided on another IO pin if needed (Rx works on the standard pin). CPU usage varies with visible screen area but is self limiting about at about 80%. A small active screen uses under 10% of the CPU cycles, with a large screen plus audio around 50% is common. Key library structures and routines are redefined each compile for efficiencies. MRETV can be turned on and off ( 0% CPU).
I have truly enjoyed reading about, constructing, and learning with Instructables. I want to take this opportunity to thank all those who have shared with me, and those who made the sharing possible. You have solved my problems, fed me, inspired me, and shown me how to do what I thought was impossible. As part of that thanks I offer the MRETV debut to the Instructable community.
This Instructable is a Build and Introduction rather than an exhaustive explanation of MRETV. You will quickly have both sound and video from your Arduino. You will have some games to play, and some useful utilities. More importantly you will have a full featured library to use sound, video and more in your own sketches. If there is interest future tutorials on the software interface are possible, it has more depth than can be explored here. Since even this build and introduction covers a lot of material, I suggest you first make the video and sound circuits then take a break and spend some time with the software examples. You can use a terminal program like 'Putty' to explore until you build the keyboard (PS/2) circuit. After making the keyboard circuit you will have all the major parts of MRETV (to use examples like Ponguino and Diode Calibration you need to build some sensors.) Please do not redistribute this Premiere Release of MRETV yet, wait till the bugs become documented features.
I have tested many versions of this project connecting to many different devices and never caused any harm to the Arduino or the other device. Most TV's hold the MRETV signal much better than the capture card I used to make the videos. Due to its simplicity, most of the time, newly built MRETV hardware works the very first try. However ...
Build and use at your own risk. I assume absolutely no liability of any kind for anything you ever do related to MRETV.
Go ahead and watch the second video then let's get building.