project page at savannah.nongnu.org

Stribog the attitude sensor homepage

• What it is
• Why you may want to get this stuff
• Project structure
• Hardware description
  1. Processor
  2. Sensors
  3. External data
• Getting the sources
• Some data captured with stribog
• Brief report of field tests on Oct 13, 2007

What it is

Stribog is an attempt to implement a platform for measuring user orientation relative to sides of world: azimuth, pitch and roll. the hardware includes a 3-axis magnetoresistive compass, a tilt sensor based on accelerometer ICs and a microcontroller to manage all.

Why you may want to get this stuff

You may be interested in the project in it's current state if you are looking for

• a sample software running on LPC213x microcontrollers built with a free toolchain
• an hardware project implementing an advanced technique for Earth field measurements via Honeywell magnetoresistors
• a design for board with IC-based attitude sensors; the board is capable to input GPS sensor data and output the combined data through an RS-232 UART

Project structure

This project consists of hardware and software sections. the former is designed with gEDA, the latter with GNU toolchains.

The whole design is distributed under the GNU GPL v3 "or later".

Hardware contains a 3-axis (magnetoresistive compass, accelerometer, optionally gyroscope) and an ARM-based microcontroller to manage all.

Software includes programs for MCU to test and align hardware parts, to perform the measurements; the software part also has some programs for POSIX host to receive obtained data.

Hardware description

Processor

Stribog is primarily designed on LPC2138. these ARMs could run at 60MHz, but this rate is limited by ROM and peripherals.

The main board has an I2C and two RS-232 ports.

Sensors

Magnetoresistive sensors are Honeywell HMC1022 and HMC1021Z. Philips make cheaper almost pin-to-pin analogs, but we have never test them. we use most precise measurements technique: the output value is the offset straps current when the bridge signal is zero. the samples rate is 800 Hz, which approaches to set/reset strap current limit.

Accelerometers are Analog Devices ADXL210AE (PWM outputs are used). ADXL202 are pin-to-pin compatible, with a more narrow measured acceleration range.

Angular rate sensors ADXRS300 can be added optionally.

External data

Since the on-board sensors can't provide the full orientation, stribog is designed to use external sensors. The data of the external sensors can come through the RS-232 ports. as of Feb 2008 we were used to connect to our main board a GARMIN GPS25 LP series receiver and a car odometer. to transform the odometer pulses into RS-232 messages and transmit them together with the GPS receiver data, a simple AVR-based board was soldered. the schematic diagramme and the firmware sources for this board form an auxiliary part of the project.

Last modified: 17 Apr 2008

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Copyright (C) 2008 Ineiev <ineiev@users.sourceforge.net>

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