MiniMag

Overview

MiniMag Magnetometer

The Avionics Anonymous MiniMag Magnetometer is a high-precision magnetometer for small unmanned aircraft. It includes a high-quality Memsic MMC5983MA magnetometer enabling sub-1-degree heading accuracy. This interfaces to your autopilot via robust UAVCAN interface - no sketchy I2C wiring for your magnetometer!

What makes it special?

  • Extremely high-quality Memsic magnetometer IC allows better than 1-degree heading accuracy in low-interference installations

  • Robust UAVCAN interface is compatible with most Pixhawks and similar autopilots and makes it safe to install your laser far away from the autopilot, wherever is convenient!

  • Mount with screws through mounting ears or snip them off and foam tape it to your airframe

  • Update firmware via CAN interface

Specifications

  • Weight: 3.2 grams

  • Size: 1.25in x 0.75in x 0.25in

  • Power: 4.0V to 5.5V, XXmA

Required Accessories

  • CAN Harness - connects between the autopilot and a CAN node and between each CAN node on the bus

  • CAN Terminator - connects to the last device on the CAN bus

Where to Buy

User Guide

Wiring

The MiniMag is connected to your autopilot via CAN bus. The wiring is per the pinout below, or the necessary cables can be purchased to connect to your system right out of the box:

  • CAN Harness - connects between the autopilot and a CAN node and between each CAN node on the bus

  • CAN Terminator - connects to the last device on the CAN bus

Pinouts

CAN Connector

Pin

Name

Description

1

POWER_IN

Power Supply. 4.0-5.5V supported.

2

CAN_H

CAN high

3

CAN_L

CAN low

4

GND

Signal/power ground.

Mounting

Attachment

The MiniMag can be mounted several ways. It includes 4x screw holes for 4-40/M3 screws. If using screws, make sure to use aluminum or otherwise non-ferrous screws! You can also simply adhere it to your vehicle with double-sided tape, and if doing so, you can cut off the mounting ears to save some weight and space.

Orientation

The MiniMag is normally mounted with the "flat" side down (components on the board pointed up) and the connector-end of the board pointed toward the back of your vehicle.

Mounting Orientation and Rotation Param

It can, however, be mounted in any orientation. If mounted flat-side-down and only rotated in yaw, you can use the built-in rotation parameter to adjust for this. Enter the value (in degrees) that the board is rotated in yaw. For example, if the connector-end of the board points toward the left side of your vehicle, enter "90" for rotation.

For mounting orientations other than simple yaw, please use the external mag rotation settings in your autopilot to match your mounting.

Configuration

Autopilot Configuration

PX4

Several autopilot parameters must be set using QGC or similar:

  • UAVCAN must be enabled by setting UAVCAN_ENABLE non zero. Set this to 1 for basic functionality or 2 to allow the device's UAVCAN parameters to be accessed via QGC.

Node Configuration

The MiniMag node has a number of parameters accessible via the UAVCAN interface. These may be set following the steps outlined here

Parameters

Parameter Name

Description

Default Value

Allowable Values

node_id

Node ID for this device

102

1-125

rotation

Board rotation in degrees

0

0-360

update_rate_hz

Rate at which magnetic field data is published in Hz

30

1-30

auto_mag_set

Enable auto temperature compensation

0

0-1

Automatic Temperature Compensation

Setting the "auto_mag_set" parameter to 1 enables an experimental automatic temperature compensation. When enabled, every 10 seconds, the unit evaluates its internal temperature. if it has changed too much, the unit performs an automatic reset and set of the polarity of the sensing film and uses this to update thermal correction offsets. If the sensor undergoes significant changes in ambient temperature, this can dramatically improve stability and accuracy of its output, but also leads to small step changes in the magnetic field output when the offsets are updated. This will pose no issue for PX4 autopilots which fuse magnetic data into a Kalman filter, but you should ensure this behavior is safe in your application. Please contact us for more information.

Warning This feature has not been thoroughly vetted and is considered experimental! Use at your own risk.

Firmware

Release Notes

v1.3

  • Reset sensor magnetization on boot

v1.2

  • Improved firmware version reporting via CAN to support PX4-based firmware update

  • Fix timer rollover issue which could cause a failed mag sample every ~72 minutes

v1.0

  • Initial Release