Android/RPi HDMI switch controller using RS232

This project shows how to connect a pretty cheap RS232 interface-based 4x2 HDMI switch to an Android phone via a Raspberry Pi

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Control Monoprice 4x2 True Matrix HDMI switch from an Android device via Raspberry Pi serial interface (python code) using the SSH Button Android app.


Monoprice wiring diagram for RS232 cabling

Adobe Portable Document Format - 12.57 kB - 12/22/2016 at 16:35



RS232 to TTL user guide

Adobe Portable Document Format - 245.95 kB - 12/22/2016 at 16:34



RS232 to TTL adapter schematic

Adobe Portable Document Format - 74.57 kB - 12/22/2016 at 16:33



Monoprice RS232 protocol description for the switch

Adobe Portable Document Format - 262.30 kB - 12/22/2016 at 16:33


  • Notes and extensions

    Paul Whitaker12/22/2016 at 17:14 0 comments

    Got the connections and code done in about 6 hours. Turning off Bluetooth and understanding the wiring of the monoprice were the biggest challenges, especially since it took a while to find the wiring document online.

    I had a straight RS232 cable but the monoprice needs a sort-of crossover cable so I'm using jumpers. Could probably hack away at the cable I have.

    The comms is really basic 9600 8N1, so it could probably be shrunk a lot with an Arduino or maybe there's something with RS232-to-TTL built in.

    There are different versions of the android app, one I used a while ago allows a popup that returns status.I thought an indicator of the current status would be useful, but you can just tap the button for the one you want if you're not sure (i.e. if the screen is black).

    Other ideas:

    • Google Home integration
    • Have a single button turn the device power on, wait a bit, then switch HDMI to it.
    • Set a cron job to return it to the Fire TV at 3AM, since that's usually what we want to start with.
    • Switch to Xbox One when we're getting an incoming Skype call
    • Integrate with Cortana since the Xbox is sitting there listening anyway
    • Some audio playback cue when switching "OK, switching to Xbox One" in the Google voice would be neat

View project log

  • 1
    Step 1

    Format a new SD card using SDFormatter

  • 2
    Step 2

    Install NOOBS onto the SD card

  • 3
    Step 3

    Connect Ethernet, HDMI, keyboard, mouse and install Raspbian Lite

View all 12 instructions

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