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Monday, 23 December 2013

RemotePi Board power IR switch for Raspberry Pi [day 11 of 20-days-of-posts series]

A power switch was omitted in the design of the Raspberry Pi to keep costs down.  There was no easy interface provided to add one either, but there are many different options.  I had previously tackled the original topic in a previous post, comparing a few options, including building your circuit.

I had previously reviewed several different Raspberry Pi switches.  A new one came to my attention that I placed an order for.  It is the RemotePi Board by MSL Digital Solutions.

At its core, it promises the same functionality has the other board solutions that intercept the micro USB power connector on the Raspberry Pi, which is to control the power on/off state of the Pi through a switch and through software.  But instead of intercepting the power flow through the micro USB power connector, it controls the power through the GPIO.  Instead of connecting your power to the micro USB power connector on the Raspberry Pi, you connect it to this board.  You then either toggle the power state by pressing the black button on the top, or better, you can use a IR remote to toggle the power.

And there lies one of the key differentiators.  For application use-cases such as a media player where you need an IR receiver, this board accomplishes that purpose as well.  I discussed how you could construct your own IR receiver setup on the GPIO in a previous post, and also talked about HDMI CEC in the same post, but one of the issues that remains in either the case of adding an IR receiver or using your TV's built in HDMI CEC support (if it has it), is that you can't power on or off your Raspberry Pi using either your Pi or TV remote.  Your solution options were either to always leave the Raspberry Pi on, have it automatically turn on when your TV is on (either by a power bar or plugged into the USB service port on your TV) or manually turn it on using a hardware switch or plug when you want to use your Pi.

I don't always watch all my media content through the Raspberry Pi (such as when I play video games, watch TV channels etc), so I resorted to using the illuminated switch bundled with my IR receiver that allowed me to keep my Raspberry Pi off, when not in use, and turn it on manually by pressing the switch when I wanted to watch some Pi content.  There were a couple times I wanted to be able to use my Logitech Harmony remote to turn on the Pi.  One of the benefits of this switch implementation is that it will use the IR remote's power button to toggle the power to the Pi.  The IR receiver on the board will also work like any standard /dev/lirc device, meaning that it could replace the IR receiver I had setup on my Pi -- that it was completely compatible with XBMC.

The switch and IR receiver is contained on a single logic board.  It has a connector port that plugs directly into the GPIO.  This wasn't a concern for me, since on my XBMC Raspberry Pi units, I only use the GPIO for two purposes -- hooking up a power switch and hooking up a IR receiver.  The direct connection to the GPIO eliminated some wiring that I needed to contend with with the IR receiver and previous power switch.  The board also came with a screw with some watches and nuts so that it could be securely mounted directly onto the mount hole on the Raspberry Pi.  The first releases of the Raspberry Pis (the model B 256MB "rev 1") don't have this mount point but the board is still usable without the mount..

I decided to integrate the board with my model B bedroom TV Raspberry Pi case.  I had reviewed the lego case I had constructed for that project in a previous post.  I had still not integrated any power switch into this unit, so I was eager.

To keep inline with the pros and cons list I provided for the other switch mechanisms, here are the lists:

  • very small
  • may need some modification to your raspberry pi case, but otherwise fits within the existing case (doesn't extend out from the board's footprint)
  • addresses the CLEAN SHUTDOWN and POWER OFF requirements fully
  • no issues with provided switch script (for other switches, I had problems and I had to make customizations to the scripts provided by other offerings)
  • fully integrated IR receiver that can be used to allow your IR remote to control XBMC
  • everything fully assembled


I took apart my case's right wall to accommodate the new higher-oriented micro USB port.  I would be revamping the case completely now that I no longer needed to snake my IR receiver around to an opening on the front of the unit, I could now also drop down the height of the case due to the same reason and I would need to accommodate the hardware button to accommodate the manual switch.

The instructions provided were very simple.  After I applied the screw and plugged in the board, I connected the micro USB power to the board's port.  Immediately I saw the built in power LED flash green and red momentarily to indicate the unit had power.  I then press and held the power switch button down for 15 seconds, at which time the LED blinked between red and green continuously, indicating that it was ready to read the IR remote command for the power button.  I used the Logitech Harmony power button that had been setup for the WD TV remote profile that I had setup previously on the unit's previous IR receiver.  It really doesn't even have to be a power button -- it can be any unused button.  The blinking stopped and I could then press that button to turn on the unit.

When the IR power-assigned-button is pressed, the board's onboard LED starts blinking green, while the Raspberry Pi turns on.  Everything booted up as it would regularly.  I didn't have to make any changes to my lircd.conf profile.  I started using the unit as I normally would.

The blinking -- which is more of a "pulsing" -- for up-to-one minute on startup and shutdown give an indication that the command was received and also indicates that the unit won't respond to subsequent power on/off requests from IR during that period.  This prevents accidentally sending a second power on/off command to the unit while it works on the initial request.  It also prevents "repeating" if the IR remote sends the same commands multiple times.  .

If you are implementing this as a new IR implementation (not replacing an existing setup), you'd need to setup a remote and lircd.conf.  I discussed how to do this in a previous post.

I had no problem using the onboard IR receiver with all my Harmony remote commands or with the WD TV remote that I keep around as a backup to control the unit when my Harmony remote is lost in the room-somewhere or is charging.

To power off, I pressed the power button again.  The board passes on all the IR signals received to the Raspberry Pi, including the one assigned to the power button, but it will start triggering a shutdown when the power-assigned button command is received.  It does this by the script that is installed as part of the setup.  It closely resembles the safe shutdown script ( that I discussed using with the other power switches.  The board's LED flashes red while the board shuts down the Pi.  It continues to monitor the Raspberry Pi's shutdown for up to a minute.  When the Pi is safely complete it's shutdown, the power is cut off (so the Pi becomes powered off), and the onboard LED turns off.  You can then use either the manual power button on the board or again the IR remote's power-assigned button to turn the Raspberry Pi back on.

The onboard LED proved to be a great asset to this power switch.  I no longer had to position the front-face position in my original lego case:

I retweaked the right-side of the case to become the new front-end of the unit.

The before:

The after:

I placed a white window block where the onboard LED is positioned, that gives the unit a nice glow when lit.  I placed an inset blue window piece for IR window.  The IR range provided by the window is adequate enough to get at least a 45 degree angle using the remote.  I moved up the blocks for the micro USB power port to line up with the new port.  I also added some support around the SD card as it was previously hanging out of the system.  It is now protected from being hit (and damaging the SD card port).

A closer view:

I revamped the top of the case to integrate the power button as well:

I review all the changes I made to my Raspberry Pi lego case for this board in this follow-on post.  In general, it is very easy to integrate the board into most cases as it doesn't change the footprint size of the Raspberry Pi.  The only customizations that are needed are:

  1. hole on the top for the manual power switch,
  2. relocation of micro USB power source in a higher position and
  3. uncovering for IR and LED visibility.

1 comment:

  1. Hey there,

    Just to let you know: it is your posts that convinced me to buy this IR solution for my PI.. It is shipping, really eager to see it all work. Thanks for your posts!