Freerunner Navigation Board v2

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Note: a new hardware revision will be available soon: the Freerunner Navigation Board v3!

The second version of the Freerunner Navigation Board includes lots of new stuff to play with, while still providing the same feature set as the first version.

Freerunner Navigation Board v2



The FRNBv2 realizes all features from the first version on the top side of the PCB. The bottom side is all about further expansion. Most of these chips are not very usable without connecting additional electronics to them. I'll add detailed descriptions of what I did with them to this page.

Top side

3D Gyroscope ITG-3200

The new ITG-3200 digital gyroscope detects rotations and measures their angular velocity. This enables the FR to be used as game controller or to improve navigation capabilities without GPS.

3D Magnetometer HMC5843

A magnetometer senses magnetic fields. It can be used as compass for navigation purposes or to sense fields from other magnetic sources.

Air pressure/temperature sensor: BMP085

A pressure sensor can be used for weather forecast or to measure the height above sea level if the pressure at sea level is known. If the height is known from other sources (e.g. GPS), the change in ambient pressure can be used to detect weather changes. This may be useful for gliding.

Bottom side

4ch Programmable LED Controller PCA9632

This chip can source or sink current for up to four LEDs with a maximum of 25mA per LED. In addition to simple on/off states it can be programmed to blink or dim individual channels or a group of channels. Since the chip does everything on its own, it will continue to work even if the host cpu suspends. This allows the often requested feature to drain the battery even faster to notify users of incoming SMS or missed phone calls by blinking a LED even if the phone is suspended. A blink frequency down to once every 10 seconds and a widely adjustable duty cycle allows for very short flashes to save battery power.

1kHz – 68MHz Programmable oscillator LTC6904

This is, well, a programmable oscillator from which one frequency output and the output enable pin are available at testpoints. My intention was to use it as 38kHz oscillator to generate the carrier frequency of common infrared remote controls. The output enable can be connected to a GPIO. After implementing a small driver, this should work as a generic remote control solution using lirc.

12 bit Analog to Digital Converter ADS1015

This is similar to the chip which was used on the FRNBv1 to digitize analog gyroscope outputs. It provides only 12 instead of 16 bits of resolution, but this should be enough for most applications. The FRNBv2 does not use it for own purposes, so it is completely under user's control.

Touch Sensor MPR121

The MPR121 from Freescale Semiconductor is a multi channel proximity capacitive touch sensor controller. Up to twelve sensor areas could be connected, but due to space restrictions, only seven channels are accessible at solder pads. It is not guaranteed that the chip will work as intended, but I think it's worth to test it. The Datasheet can be found here.

Expansion pads

The supply voltage as well as the I2C bus is routed to testpads at the end of the board. These enable easy further expansion with more I2C devices (e.g. a digital humidity sensor)


Schematic and board layout files are available in CadSoft EAGLE 5.x format from


Pinout: Bottom side, Top side
I2C testpoints
  • VCC: +3.3V, available at the AUX-Switch
  • GND: Ground, available from the (big) decoupling capacitor next to the accelerometer
  • SCL, SDA: Serial clock and data, get it from testpoints at the debug connector
  • OE: Output enable from the frequency generator. Pull this pin high to enable the CLK output
  • CLK: Clock output from the frequency generator.
  • LED controller 0-3: LED current sinks. Connect LEDs in series with current limiting resistors from VCC to these pads.
  • 12-Bit A/D 0-3: Analog to digital converter inputs. They can operate single ended or differencial. The reference voltage is VCC.
  • Touch electrodes 0-6: Connect these pads to a larger conducting area to use it as touch sensor. The inputs 0-3 can also be used to drive LEDs. Refer to the datasheet for more information.
Top side with the BMP085
Bottom side with PCA9632 and LTC6904. The LED controller works :)


Hardware installation

The best way to connect the FRNBv2 to your Freerunner is to solder four wires to the VCC, GND, SCL and SDA pads at the top side of the board. SDA and SCL are available at test points next to the debug connector. VCC is accessible at the AUX switch. GND is available from the big decoupling capacitor below the backup battery.

The FRNBv2 can be mounted into the free space below the GPS connector. I would reccomend to apply some adhesive tape to the GPS connector and the metallic cover on the main pcb. It prohibits short circuits which cause damage to the Freerunner or the FRNBv2.

Here is a PDF with an overview of the Installation.

Software installation

Boot your OS and run

i2cdetect 0

It should display a table with all I2C adresses for which a device is connected to your Freerunner: (TODO: example)

You should find all adresses listed below.

Test Status

The first PCBs arrived and allows to test single features. The progress will be documented here.

Chip I²C address Test Result Notes
ITG3200 0x69 ok driver usable but still incomplete
HMC5843 0x1E ok driver should to degauss sensor to ensure proper operation
BMP085 0x77 ok
PCA9632 0x60 ok
LTC6904 0x17 ok works with 15pF cap between SCL and SDA (NOR boot fix)
ADS1015 0x40 ok kernel driver incomplete. Userspace driver incomplete
MPR121 0x5A ok works, hackish driver available


Known HW or SW Issues

  • LTC6904
The frequency generator LTC6904 consumes about 0.5mA even if the outputs are turned off. This is not a real bug but it would be nice to turn the chip off while unused. A small modification should make it possible to use one output from the LED controller to control the power.
The chip works with the NOR-Boot fix described below.
Reading exactly two bytes from the LTC6904 causes the I2C bus to lock up. The stop condition is not sent correctly and the master does not stop generating a clock. The chip works fine when programmed with a MSP430 microcontroller. Therefore either the Linux driver or the Samsung SoC (or both) are causing the bug. I'll try to resolve this, but I'm quite busy with other stuff. If someone wants to help, please contact me.
  • ITG3200
Use *50V* 2.2nF capacitor for C5. fixed.
  • General
NOR-Boot does not work if the FRNBv2 is connected. If you need the NOR boot only as emergency recovery, hold your finger onto the I2C-SCL pad (pay attention to ESD!) or connect the debug board cable (no need to connect the real board, the cable is enough) to "fix" the issue.
Of course, this issue can be fixed permanently with an additional capacitor ;-) Solder a 15pF cap between SDA and SCL. A 0402 sized capacitor fits easily onto the test points at the edge of the board.


Kernel drivers

This gitorious page lists all currently available drivers for the FRNBv2. The kernel drivers for the BMP085 and the HMC5843 are already upstream and will be shipped with kernel 2.6.36. All other drivers need some cleanup and more documentation to be accepted. I will try to get this done. If you're bored and want to help, please do so!


The compass driver reports wrong values. The latest patch swaps MSB and LSB. Now it returns more meaningful values. There may be more bugs left. For reference you may have a look at another driver which is already upstream: hmc5843.c bvg

Userspace software


The sensor-monitor is an excellent application to test the different sensors. Alternatively cat and echo can be used to communicate with them. Right now the interfaces to userspace lack some documentation. Either look at the source code or ask me if you are in trouble.


This program provides altitude or weather information on Neo Freerunners with bmp085 pressure sensors installed. The bmp085 is available as part of the Freerunner Navigation Board. Source code and binaries can be found here.


ValaCompass is a minimalistic 3D compass application written in Vala that displays the North direction considering the pitch and roll orientation of the handheld.


The team kindly offered to retail the FRNBv2. You can find it here.

Two assembly options are available:

  • Complete: everything you (possibly) want. Contains all chips as described above.
  • Standard: contains everything except the frequency generator and the analog to digital converter.

Possible packaging options:

  • CAB: Completely assembled board. Just add some wires and you're ready
  • DIY: Do it yourself! The PCB and all components needed to get your hands dirty
  • PCB: The bare PCB. You are free to buy only what you need.

Right now, only the CAB boards can be ordered online. If you just want the PCB and/or a few parts, contact me or the nice staff at

User Reports

Please write to the discussion page.

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