Would you like to use a remote control to control your computer? How about using your computer to send remote control signals to your TV or Stereo instead of using the remote?
This is the first in a series of posts where I will describe how to use a Raspberry Pi, Raspbian and Linux Infrared Remote Control (Lirc) to receive and send infrared remote control signals. This first post will be focused on setup and receiving input.
Linux Infrared Control Posts
Linux Infrared Remote Control (Lirc) has been around for many years and is an example of a ‘traditional’ unix application: it can do many things and is tricky to setup (the documentation even says a much). With a Raspberry Pi and a few cheap electrical parts it is possible to create a custom remote control or have your computer respond to your existing remote.
The presence of the general purpose input output (GPIO) pins on the Raspberry pi allows the control of external circuits from a linux computer. These instructions will use Linux Infrared Remote Control (Lirc), a well established and tested collection of applications, to receive input and send output.
Raspberry Pi Models
A quick note about Raspberry Pi models. All Raspberry Pis have a row of GPIO pins, but depending on the model, some of have either 26 or 40 pins. To confuse things a little more, early models changed what some pins did.
In an attempt to keep things simple, these instructions will use the following pins which are the same across all models:
- Pin 8 (GPIO 14) for input
- Pin 1 for input power
- Pin 6 for input ground
- Pin 10 (GPIO 15) for output
- Pin 2 for output power
- Pin 14 for input ground
It should be noted there are two ways to refer to the pins. One way is by pin number, starting at 1, labeled on the board with P1. A second way is by pin function, such as GPIO1, TXD0 etc. FYI there are multiple GND, +3V3 and +5V pins. These instructions will be using pin numbers.
Install & Update Raspbian
Rather then re-hash how to install Raspbian on a SD / MicroSD, please see the official instructions. Use Etcher, it makes things much easier and less likely to make your computer unbootable.
Testing was done with 2017-09-07-raspbian-stretch-lite, which included lirc version 0.9.4c.
Different versions of Raspbian or lirc may have different results.
After installing, connect the Raspberry Pi to the internet and login.
First change your password.
Optionally enable ssh, run `raspi-config`:
Select `Interfacing Options`, select `SSH`, Enabled `YES`. Also at this point consider changing your hostname and any localization settings.
Apply all updates:
sudo apt-get update && sudo apt-get upgrade -y sudo apt-get dist-upgrade -y sudo apt-get autoremove -y
Previously it was recommended to install and run rpi-update, which updates the firmware and kernel, this is no longer recommended.
As a result of running rpi-update, test and developmental firmware and kernels were installed, which can be unstable and some do not include the lirc drivers. As a result it is no longer recommended to run rpi-update.
Reboot to make sure changes are live:
Finally, install lirc:
sudo apt-get install lirc -y
This installs version 0.9.4c of the lirc package.
Configure Rasbpian and Lirc
Edit `/boot/config.txt` to configure gpio pin 14 (input):
sudo vi /boot/config.txt
#dtoverlay=lirc-rpi # ADDED dtoverlay=lirc-rpi dtparam=gpio_in_pin=14
Edit `/etc/lirc/lirc_options.conf` to configure to use the Raspberry Pi GPIO pins by changing the `driver` from `devinput` to `default`:
sudo vi /etc/lirc/lirc_options.conf
# These are the default options to lircd, if installed as # /etc/lirc/lirc_options.conf. See the lircd(8) and lircmd(8) # manpages for info on the different options. # # Some tools including mode2 and irw uses values such as # driver, device, plugindir and loglevel as fallback values # in not defined elsewhere. [lircd] nodaemon = False # CHANGED #driver = devinput driver = default device = auto output = /var/run/lirc/lircd pidfile = /var/run/lirc/lircd.pid plugindir = /usr/lib/arm-linux-gnueabihf/lirc/plugins permission = 666 allow-simulate = No repeat-max = 600 #effective-user = #listen = [address:]port #connect = host[:port] #loglevel = 6 #uinput = ... #release = ... #logfile = ... [lircmd] uinput = False nodaemon = False # [modinit] # code = /usr/sbin/modprobe lirc_serial # code1 = /usr/bin/setfacl -m g:lirc:rw /dev/uinput # code2 = ... # [lircd-uinput] # release-timeout = 200
Reboot to make the changes live:
Shutdown the Raspberry Pi whenever connections are made to the GPIO pins.
First buy a breadboard, leads and infrared receiver. The receivers are cheap, around $2.00.
This hardware will be to prototype the circuit and will not require soldering.
Setup the sensor on the breadboard. There are three leads, if you are using the TSOP38238, lens (‘bump’ on sensor) facing up and should be connected as follows:
+-----------------------+ A | +-----------o +3.3V, Pin 1 | | | ______________ | | / | | ( | B | \______________ + +-----------o GND, Pin 6 | | | | C | - +-----------o GPIO 14, Pin 8 +-----------------------+ Pin 1 Pin2 +3V3 [A] [ ] +5V SDA1 / GPIO 2 [ ] [ ] +5V SCL1 / GPIO 3 [ ] [B] GND GPIO 4 [ ] [C] GPIO 14 / TXD0 GND [ ] [ ] GPIO 15 / RXD0 GPIO 17 [ ] [ ] GPIO 18 GPIO 27 [ ] [ ] GND GPIO 22 [ ] [ ] GPIO 23 +3V3 [ ] [ ] GPIO 24 MOSI / GPIO 10 [ ] [ ] GND MISO / GPIO 9 [ ] [ ] GPIO 25 SCLK / GPIO 11 [ ] [ ] GPIO 8 / CE0# GND [ ] [ ] GPIO 7 / CE1# Pin 25 Pin 26
Original ASCII art from:
The wiring should look like:
Receiver Software: Testing with mode2
Now that the circuit is complete, next step is to test the reception of remote control button presses
First stop lirc, if running:
sudo systemctl stop lircd.socket sudo systemctl stop lircd.service
Second, start `mode2`, which will listen for pulses from the sensor.
mode2 -d /dev/lirc0
On start you should see:
Using driver default on device /dev/lirc0 Trying device: /dev/lirc0 Using device: /dev/lirc0
Point remote at receiver, begin pressing buttons. If you see a series of lines like the following, then the circuit is working:
space 10607416 pulse 4503 space 4442 pulse 564 space 1662 pulse 561 space 1657
Press `control c` to exit mode2.
Receiver Software: Capture with irrecord
Next we will create a lirc configuration file for your remote.
As a result of the large number of different remotes with buttons, lirc defines a standard set of button names (commonly referred to as a namespace), the current namespace has over 500 button names. A typical remote will only have a small subset of these names.
To see the list of standard button names, type:
Based on the remote being captured, it is worth taking a few minutes and plan out which buttons names should be used.
Existing Remote Configurations
The lirc project does ship with some remote configurations already captured, see `/usr/share/lirc/configs`
Once captured, these button presses can be used to either send out the same button presses using an ir transmitter (sometimes referred to as a irblaster) or listen and execute programs when the button presses are received.
As a demo, we are going to capture the power button on the remote, this is the KEY_POWER in the name space. In part 2, this button press will be transmitted to demo `irsend`.
First stop lirc, if running:
sudo systemctl stop lircd.socket sudo systemctl stop lircd.service
Second, start `irrecord` and specify an appropriate conf filename:
irrecord -d /dev/lirc0
On start the example output look like:
Using driver default on device /dev/lirc0 irrecord - application for recording IR-codes for usage with lirc Copyright (C) 1998,1999 Christoph Bartelmus(firstname.lastname@example.org) This program will record the signals from your remote control and create a config file for lircd. A proper config file for lircd is maybe the most vital part of this package, so you should invest some time to create a working config file. Although I put a good deal of effort in this program it is often not possible to automatically recognize all features of a remote control. Often short-comings of the receiver hardware make it nearly impossible. If you have problems to create a config file READ THE DOCUMENTATION at https://sf.net/p/lirc-remotes/wiki If there already is a remote control of the same brand available at http://sf.net/p/lirc-remotes you might want to try using such a remote as a template. The config files already contains all parameters of the protocol used by remotes of a certain brand and knowing these parameters makes the job of this program much easier. There are also template files for the most common protocols available. Templates can be downloaded using irdb-get(1). You use a template file by providing the path of the file as a command line parameter. Please take the time to finish the file as described in https://sourceforge.net/p/lirc-remotes/wiki/Checklist/ an send it to
so it can be made available to others. Press RETURN to continue. Checking for ambient light creating too much disturbances. Please don't press any buttons, just wait a few seconds... No significant noise (received 0 bytes) Enter name of remote (only ascii, no spaces) :example Using example.lircd.conf as output filename Now start pressing buttons on your remote control. It is very important that you press many different buttons randomly and hold them down for approximately one second. Each button should generate at least one dot but never more than ten dots of output. Don't stop pressing buttons until two lines of dots (2x80) have been generated. Press RETURN now to start recording. ................................................................................ Got gap (46527 us)} Please keep on pressing buttons like described above. ............................................................................... Please enter the name for the next button (press to finish recording) KEY_POWER Now hold down button "KEY_POWER". Please enter the name for the next button (press to finish recording) Checking for toggle bit mask. Please press an arbitrary button repeatedly as fast as possible. Make sure you keep pressing the SAME button and that you DON'T HOLD the button down!. If you can't see any dots appear, wait a bit between button presses. Press RETURN to continue. ..............................Cannot find any toggle mask. Successfully written config file example.lircd.conf
And that is it! Hopefully you have a really simple circuit that is capturing the IR signals from your remote. Next we will transmit this button press back to power on or off the device the remote controlled.