Month: September 2013

Debian on Ouya: All Systems Go

tuomas

I finally got all the major subsystems working and Debian is now usable on Ouya. I prefer Debian but Ubuntu should work similarly.

Working video and 3D

In the above screenshot I’m playing 1080p H264 while running glmark2-es, an OpenGL ES benchmark. And the CPUFreq ondemand governor doesn’t even raise the CPU frequency from the minimum as everything is properly accelerated. I do have to admit that the 1080p video isn’t running smoothly with the benchmark running at the same time.

A disclaimer before telling more: Trying this out might void the warranty and flashing anything to Ouya may easily brick it forever. So don’t try it, unless you are willing to buy a new one.

That said, the idea is not to touch Ouya’s Android at all. Kernel is booted from RAM and Debian from an SD card or USB stick.

The instructions for debootstrapping your own Debian Wheezy rootfs are described in the github repository and the needed binaries are in a temporary location that will probably change at some point.

WiFi is working as well but I’m not sure if the firmware binaries are redistributable, so you need to copy them from the Android rootfs after booting to Debian.

One of my main goals for this whole exercise is video encoding and I’m happy to say that H264 encoding from an USB webcam works nicely with hardware acceleration as well.

I’ve also noticed some issues:

  • Hciconfig doesn’t show BT devices, I didn’t debug much further.
  • Mpg123 seems to play but nothing is heard. Maybe it tries to pass MP3 onwards instead of PCM? GStreamer provides acceleration for MP3 and AAC though.
  • Video acceleration works only with GStreamer and nvxvimagesink. Mplayer can’t even use XV video output correctly.
  • Tegra3 supports only OpenGL ES 2.0 with EGL, so no full OpenGL with GLX.
  • Xrandr seems to be able to switch the resolution but after the switch there was window decoration corruption.

Despite the deficiencies I think Tegra3 is quite well supported in the X.Org world and many things work well with this 99$ device.

If you test my instructions, let me know how it goes and what you think about it! :)

Pleco Phase02 completed

tuomas

It’s been two years already since I posted about Phase01 being completed. It was a simple track based vehicle using cheap DC motors and the hull was built from Meccano parts:

Pleco Phase01

For Phase02 I decided to go with a ready made car and bought an RC Rock Crawler. It’s about four times the size of the Phase01:

Pleco Phase02 open

Pleco Phase02

The software is roughly the same as it was for Phase01. I’ve fixed a lot of bugs, simplified some things and added a bunch of new features. The slave has a sonar next to webcam and it measures the distance to what ever the camera is pointing at. The slave also measures the current consumption and battery voltage level. All details are shown on the GUI.

The hardware on the other hand has changed a lot. Instead of handling the servos directly from Linux there’s now a separate self-designed Cortex-M4 based microcontroller board for driving the PWM signals. In the future the microcontroller can update the PWM signals real-time based on other sensors without having to worry about latency issues in Linux.

The Linux is now running on a Tegra3 based Ouya gaming device. Ouya is not as convenient for robotics as Gumstix was but personally I think Tegra has better Linux support than OMAPs. And since there is now a separate control board for motors and sensors, it’s enough for the Ouya to only have a USB connection to the control board.

Ouya needs 12 volts while the motors need 5 volts and I’m expecting to need 3.3 volts as well. So I now have three switching regulators connected to the battery for the needed voltage levels. And a USB hub because of the USB based control board and webcam. There are also lots of cables. So I’m not actually able to get everything nicely inside the car, but almost.

Controlling an RC car with a keyboard is inconvenient, so I’ve added support for gamepads. I’m currently using a Bluetooth based gamepad from Logitech:

Logitech F710 gamepad

When driving in a local WiFi network, there’s no noticeable latency at all. It’s still not possible to really drive based on the camera only, the viewing angle is too narrow, turning the camera is cumbersome and the video quality needs some tweaking.

Now that I’ve made some nice progress with the project, I have clear goals for the Phase03:

  1. Disassemble the webcam to get the size and the weight down and to be able to attach fish eye lenses to it.
  2. 3D print a frame for the electronics and the webcam.
  3. Tweak the video quality and camera controls so that it would finally be possible to drive based on the video stream.
  4. Control the webcam based on driver’s head orientation?

So there are plenty of interesting things to learn :)

Oh, and I’ve moved the code to github.