Thanks Dave
It looks like going with a third-party GPS unit will give me more choice and should be easy to integrate.
Looking more closely at the capabilities of the RoboStix...
The ADC is (only) 10bit - Ignoring any improvements possible with dither, on a +/- 10g IMU, the precision will be only about 0.2 m/s^2 (quite poor relative to the accuracy of the accelerometers themselves). Is there a practical way of increasing this precision. If not, i will have to consider using an integrated digital IMU (something i wanted to avoid for cost and because I wantered to implment my own filters on the Robostix), or alternatively an auxiliary ADC (I assume one can buy such a thing).
Additionally, I noticed that the Robostix has 6 dedicated PWM terminals. Can I program the other GPIO pins to perform the same function (whilst carrying the power direct to the servos).
At this point I can wondering if the RoboStix is really giving me anything useful, or if indeed I am going down the right route with hardware.
07 January 2007 19:03:53
Dave Hylands (

General mailing list for gumstix users. (

Re: [Gumstix-users] Which expansion/mother boards - Autonomous Air Vehicle

Hi Mike,

> It looks like I've completely overlooked the fact that I can only connect 1
> or 2 expansion boards (Basix or Connex respectively) plus a tweener for
> RS232.
> For an Autonomous Air Vehicle:
> I'll need a wireless serial unit for comms (whose interface I am assuming
> will be an RS232).
> I'll need analogue (and probably digital) I/O for sensor inputs and
> filtering, and servo control. I wanted to use a robostix (Hirose 60-pin)
> I'll need GPS. I wanted to use a GPSStix (Hirose 60-pin, but FAQs talk about
> connection via a STUART as on the RoboStix!).
> I wanted MMC for memory expansion. I wanted to use a Basix for its
> MMC.Assuming I use a tweener for connection to my wireless serial link, I
> really think I need a Robostix for general interfacing. Does this mean I'll
> have to forgo the GPSStix or can I use it without connecting the 60 pin
> Hirose and instead connecting it to the RoboStix STUART.
> Can anyone suggest a solution? Thanks in advance

The robostix exposes the STUART and FFUART serial ports as 5v logic
level serial ports.

The GPSstix exposes all 4 serial ports as 3.3v logic level serial, but
uses the STUART to connect to the GPS.

You could connect the robostix directly to the gumstix and use another
GPS module:

Or you could plug ini the gpsstix to the gumstix and connect the
robostix vi i2c.

So the tweener basically acts like a logic-level to RS232 level
voltage converter.

You should probably check out these pages:

Dave Hylands
Vancouver, BC, Canada

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