sense hat sample “snake” returns “event device not found” error

Question

My "sense hat" sits ontop of a raspberry pi 3. I've completed the installation instructions found at https://www.raspberrypi.org/documentation/hardware/sense-hat/

lexu:~> sudo apt-get update
lexu:~> sudo apt-get install sense-hat
lexu::~> cp /usr/src/sense-hat/examples ~/ -a
lexu:~> sudo reboot

But when I try to run the 'snake' example, I get a 'Event device not found." - error. Apparently the "joystick" can't be found/read from. Here's the relevant c-code:

    evpoll.fd = open_evdev("Raspberry Pi Sense HAT Joystick");
    if (evpoll.fd < 0) {
            fprintf(stderr, "Event device not found.\n");
            return evpoll.fd;
    }

Answer 1

entering sudo chmod 666 /dev/fd1 fixed the problem!

lexu:~> sudo chmod 666 /dev/fd1

Explanation: The code examples assume that you are running either as root or as a user in that belongs to the group video. My personal user 'lexu' doesn't, so I had to change the access rights.

Answer 2

the group video is required for the LED grid.

the group input is required for the joystick and causes the error mentioned above.

don't forget to relogin after usermod.