EasyMini Owner’s Manual

The Lithium Polymer EasyMini battery can be charged by disconnecting it from the board and plugging it into a standalone battery charger such as LipoCharger, and connecting that via a USB cable to a laptop or other USB power source.

You can also choose to use another battery with EasyMini, anything supplying between 4 and 12 volts should work fine (like a standard 9V battery), but if you are planning to fire pyro charges, ground testing is required to verify that the battery supplies enough current to fire your chosen e-matches.

Next you should obtain and install the AltOS software. The AltOS distribution includes the AltosUI ground station program, current firmware images for all of the hardware, and a number of standalone utilities that are rarely needed. Pre-built binary packages are available for Linux, Microsoft Windows, Mac OSX. Full source code and build instructions are also available. The latest version may always be downloaded from http://altusmetrum.org/AltOS

To prevent electrical interference from affecting the operation of the flight computer, it’s important to always twist pairs of wires connected to the board. Twist the switch leads, the pyro leads and the battery leads. This reduces interference through a mechanism called common mode rejection.

All Altus Metrum flight computers have a two pin JST PH series connector to connect up a single-cell Lithium Polymer cell (3.7V nominal). You can purchase matching batteries from the Altus Metrum store, or other vendors, or you can make your own. Pin 1 of the connector is positive, pin 2 is negative. Spark Fun sells a cable with the connector attached, which they call a JST Jumper 2 Wire Assembly

Altus Metrum flight computers always have two screws for each pyro charge. This means you shouldn’t need to put two wires into a screw terminal or connect leads from pyro charges together externally.

On the flight computer, one lead from each charge is hooked to the positive battery terminal through the power switch. The other lead is connected through the pyro circuit, which is connected to the negative battery terminal when the pyro circuit is fired.

Altus Metrum flight computers need an external power switch to turn them on. This disconnects both the computer and the pyro charges from the battery, preventing the charges from firing when in the Off position. The switch is in-line with the positive battery terminal.

Altus Metrum flight computers include a beeper to provide information about the state of the system.

Here’s a short summary of all of the modes and the beeping that accompanies each mode. In the description of the beeping pattern, “dit” means a short beep while "dah" means a long beep (three times as long). “Brap” means a long dissonant tone.

Here’s a summary of all of the Pad and Idle mode indications. In Idle mode, you’ll hear one of these just once after the two short dits indicating idle mode. In Pad mode, after the dit dah dah dit indicating Pad mode, you’ll hear these once every five seconds.

Connect a battery and power switch and turn the switch to "on". The flight computer will signal power on by reporting the battery voltage and then perform an internal self test and sensor calibration.

Once the self test and calibration are complete, there are two modes that an Altus Metrum flight computer can operate in:

For EasyMini, if the USB cable is connected to a computer, it will enter Idle mode. Otherwise, it will enter Flight/Pad mode.

You can see in Understanding Beeps how to tell which mode the flight computer is in.

You can use an active switch circuit, such as the Featherweight Magnetic Switch, with any Altus Metrum flight computer. These require three connections, one to the battery, one to the positive power input on the flight computer and one to ground. Find instructions on how to hook these up for each flight computer below. Then follow the instructions that come with your active switch to connect it up.

As mentioned above in Hooking Up Pyro Charges, one lead for each of the pyro charges is connected through the power switch directly to the positive battery terminal. The other lead is connected to the pyro circuit, which connects it to the negative battery terminal when the pyro circuit is fired. The pyro circuit on all of the flight computers is designed to handle up to 16V.

To use a separate pyro battery, connect the negative pyro battery terminal to the flight computer ground terminal, the the switched positive battery terminal to the igniter and the other igniter lead to the negative pyro terminal on the flight computer. When the pyro channel fires, it will complete the circuit between the negative pyro terminal and the ground terminal, firing the igniter. Specific instructions on how to hook this up for each flight computer will be found in the section below for that flight computer.

Note that you must include a switch in the positive lead of the pyro battery for safety, as the on-board power switch circuit on our product only controls current flow from the the primary or system battery!

EasyMini is designed to use either a lithium polymer battery or any other battery producing between 4 and 12 volts, such as a rectangular 9V battery.

All AltusMetrum flight computers that have a radio can communicate with the ground station software for configuration and other operations using the Packet Link mode. This uses radio communication instead of a USB cable. To set this up, the ground station software must be configured to the correct data rate, frequency and callsign.

You can monitor Packet Link mode from TeleBT or TeleDongle by watching the LEDs. Each time the device transmits, the red LED will flash. When the link is busy, or when the link is not working, the device will transmit 10 times per second, so the LED will flash rapidly. When the link is working and there is no data to send, the link will flash once per second, and the LED will flash more slowly.

EasyMini has two sets of four screw terminals near one end of the board. Using the picture above, the top four have connections for the main pyro circuit and an external battery and the bottom four have connections for the apogee pyro circuit and the power switch. Counting from the left, the connections are as follows:

There are two possible battery connections on EasyMini. You can use either method; both feed through the power switch terminals.

One battery connection is the standard Altus Metrum white JST plug. This mates with single-cell Lithium Polymer batteries sold by Altus Metrum.

The other is a pair of screw terminals marked 'Battery +' and 'Battery -'. Connect a battery from 4 to 12 volts to these terminals, being careful to match polarity.

Because EasyMini allows for batteries other than the standard Altus Metrum Lithium Polymer cells, it cannot incorporate a battery charger circuit. Therefore, when using a Litium Polymer cell, you’ll need an external charger. These are available from Altus Metrum, or from Spark Fun.

As described above, using an external pyro battery involves connecting the negative battery terminal to the flight computer ground, connecting the positive battery terminal to one of the igniter leads and connecting the other igniter lead to the per-channel pyro circuit connection.

To connect the negative pyro battery terminal to EasyMini ground, connect it to the negative external battery connection, top terminal 4.

Connecting the switched positive battery terminal to the pyro charges must be done separate from EasyMini, by soldering them together or using some other connector. Note that for safety, you must put a switch between the pyro battery and the rest of the circuit!

The other lead from each pyro charge is then inserted into the appropriate per-pyro channel screw terminal (top terminal 1 for the Main charge, bottom terminal 1 for the Apogee charge).

As explained above, an external active switch requires three connections, one to the positive battery terminal, one to the flight computer positive input and one to ground. Use the negative external battery connection, top terminal 4 for ground.

The positive battery terminal is available on bottom terminal 4, the positive flight computer input is on the bottom terminal 3.

In the rocket itself, you just need a flight computer and a single-cell, 3.7 volt nominal Li-Po rechargeable battery. A 110mAh battery weighs less than a triple A battery and is a good choice for use with EasyMini.

The GUI tool, AltosUI, is written in Java and runs across Linux, Mac OS and Windows. There’s also a suite of C tools for Linux which can perform most of the same tasks.

After the flight, you can use a USB cable to plug into the flight computer board directly. A USB cable is also how you charge the Li-Po battery, so you’ll want one of those anyway. The same cable used by lots of digital cameras and other modern electronic stuff will work fine.

Our software makes it easy to log the data from each flight, both the telemetry received during the flight itself, and the more complete data log recorded in the flash memory on the altimeter board. Once this data is on your computer, our post-flight tools make it easy to quickly get to the numbers everyone wants, like apogee altitude, max acceleration, and max velocity. You can also generate and view a standard set of plots showing the altitude, acceleration, and velocity of the rocket during flight. And you can even export a flight log in a format usable with Google Maps and Google Earth for visualizing the flight path in two or three dimensions!

Our ultimate goal is to emit a set of files for each flight that can be published as a web page per flight, or just viewed on your local disk with a web browser.

Because all of our work is open, both the hardware designs and the software, if you have some great idea for an addition to the current Altus Metrum family, feel free to dive in and help! Or let us know what you’d like to see that we aren’t already working on, and maybe we’ll get excited about it too…​

Watch our web site for more news and information as our family of products evolves!

The altimeter records flight data to its internal flash memory. The 'Save Flight Data' button allows you to read the flash memory and write it to disk.

Clicking on the 'Save Flight Data' button brings up a list of connected flight computers and TeleDongle devices. If you select a flight computer, the flight data will be downloaded from that device directly.

After the device has been selected, a dialog showing the flight data saved in the device will be shown allowing you to select which flights to download and which to delete. With version 0.9 or newer firmware, you must erase flights in order for the space they consume to be reused by another flight. This prevents accidentally losing flight data if you neglect to download data before flying again. Note that if there is no more space available in the device, then no data will be recorded during the next flight.

The file name for each flight log is computed automatically from the recorded flight date, altimeter serial number and flight number information.

Select this button and you are prompted to select a flight record file, either a .telem file recording telemetry data or a .eeprom file containing flight data saved from the altimeter flash memory.

Once a flight record is selected, the flight monitor interface is displayed and the flight is re-enacted in real time.

Select this button and you are prompted to select a flight record file, either a .telem file recording telemetry data or a .eeprom file containing flight data saved from flash memory.

Note that telemetry files will generally produce poor graphs due to the lower sampling rate and missed telemetry packets. Use saved flight data in .eeprom files for graphing where possible.

Once a flight record is selected, a window with multiple tabs is opened.

This tool takes the raw data files and makes them available for external analysis. When you select this button, you are prompted to select a flight data file, which can be either a .eeprom or .telem. The .eeprom files contain higher resolution and more continuous data, while .telem files contain receiver signal strength information. Next, a second dialog appears which is used to select where to write the resulting file.

Select this button and then select an altimeter.

The first few lines of the dialog provide information about the connected device, including the product name, software version and hardware serial number. Below that are the individual configuration entries.

At the bottom of the dialog, there are four buttons:

The rest of the dialog contains the parameters to be configured.

This button presents a dialog so that you can configure the AltosUI global settings.

This reprograms Altus Metrum devices with new firmware. EasyMini is programmed directly over USB (self programming). Please read the directions for flashing devices in Updating Device Firmware.

This activates the igniter circuits in the flight computer to help test recovery systems deployment.

Selecting the 'Fire Igniter' button brings up the usual device selection dialog. Pick the desired device. This brings up another window which shows the current continuity test status for all of the pyro channels.

Next, select the desired igniter to fire. This will enable the 'Arm' button.

Select the 'Arm' button. This enables the 'Fire' button. The word 'Arm' is replaced by a countdown timer indicating that you have 10 seconds to press the 'Fire' button or the system will deactivate, at which point you start over again at selecting the desired igniter.

The AltOS firmware build for the altimeters has two fundamental modes, “idle” and “flight”. Which of these modes the firmware operates in is determined at start up time. Since EasyMini doesn’t have an accelerometer we can use to determine orientation, “idle” mode is selected if the board is connected via USB to a computer, otherwise the board enters “flight” mode. This is also how EasyMotor works, since even though it has an accelerometer, it detects the motor burn it is meant to record by detecting
a rise in chamber pressure, and board orientation doesn’t matter.

At power on, the altimeter will beep out the battery voltage to the nearest tenth of a volt. Each digit is represented by a sequence of short “dit” beeps, with a pause between digits. A zero digit is represented with one long “dah” beep. Then there will be a short pause while the altimeter completes initialization and self test, and decides which mode to enter next.

In flight or “pad” mode, the altimeter engages the flight state machine, goes into transmit-only mode to send telemetry, and waits for launch to be detected. Flight mode is indicated by an “di-dah-dah-dit” (“P” for pad) on the beeper or lights, followed by beeps or flashes indicating the state of the pyrotechnic igniter continuity. One beep/flash indicates apogee continuity, two beeps/flashes indicate main continuity, three beeps/flashes indicate both apogee and main continuity, and one longer “brap” sound which is made by rapidly alternating between two tones indicates no continuity. For a dual deploy flight, make sure you’re getting three beeps or flashes before launching! For apogee-only or motor eject flights, do what makes sense.

If idle mode is entered, you will hear an audible “di-dit” or see two short flashes (“I” for idle), and the flight state machine is disengaged, thus no ejection charges will fire. Idle mode is useful for configuring the altimeter, for extracting data from the on-board storage chip after flight, and for ground testing pyro charges.

In “Idle” and “Pad” modes, once the mode indication beeps/flashes and continuity indication has been sent, if there is no space available to log the flight in on-board memory, the flight computer will emit a warbling tone (much slower than the “no continuity tone”)

See Understanding Beeps for a summary of all of the audio signals used.

Once landed, the flight computer will signal that by emitting the “Landed” sound described above, after which it will beep out the apogee height (in meters). Each digit is represented by a sequence of short “dit” beeps, with a pause between digits. A zero digit is represented with one long “dah” beep. The flight computer will continue to report landed mode and beep out the maximum height until turned off.

An important aspect of preparing a rocket using electronic deployment for flight is ground testing the recovery system.

Just prep the rocket for flight, then power up the altimeter in “idle” mode. You can now command the altimeter to fire the apogee or main charges from a safe distance using your computer and the Fire Igniter tab to complete ejection testing.

Configuring an Altus Metrum altimeter for flight is very simple. Even on our baro-only TeleMini and EasyMini boards, the use of a Kalman filter means there is no need to set a “mach delay”. All of the configurable parameters can be set using AltosUI. Read Configure Altimeter for more information.

Self-programmable devices are reprogrammed by connecting them to your computer over USB.

Version 1.9.19

Version 1.9.18

Version 1.9.17

Version 1.9.16

Version 1.9.15

Version 1.9.14

Version 1.9.13

Version 1.9.12

Version 1.9.11

Version 1.9.10

This release contains a couple of bug fixes for ground station software.

Version 1.9.9

This release contains a critical bug fix for a problem introduced in version 1.9.8 for TeleMega and EasyMega boards. This problem occurs when using the stored configuration from 1.9.7 or earlier.

If you are running 1.9.8 or are upgrading from 1.9.8 on any version of TeleMega or EasyMega, you must reconfigure all pyro channels, recalibrate accelerometers, reset the APRS interval, adjust the beep tone and reset the pyro time.

Version 1.9.8

Version 1.9.7

Version 1.9.6

Version 1.9.5

Version 1.9.4

Version 1.9.3

Version 1.9.1

Version 1.9

Version 1.8.7

Version 1.8.6

Version 1.8.5 includes fixes to the ground software support for TeleBT v4, along with a few other minor updates.

Version 1.8.4 includes support for EasyMini version 2.0

Version 1.8.3 includes support for TeleMega version 3.0 along with two important flight computer fixes. This version also changes KML export data to make Tripoli Record reporting better and some updates to graph presentation and data downloading.

Version 1.8.2 includes support for TeleGPS version 2.0 along with accelerometer recalibration support in AltosUI.

1.8.2 also contains a couple of minor fixes for AltosUI when analyzing saved data files.

Version 1.8.1 includes an important bug fix for Apogee Lockout operation in all flight computers. Anyone using this option must update firmware.

This release also contains a change in how flight computers with accelerometers deal with speeds around and above Mach 1. In previous versions, the flight computer would completely disregard the barometric sensor above 330m/s (around Mach 1). Now, the data from the barometric sensor is reduced in effect without ever going away entirely. This prevents early drogue deployment for flights which spend considerable time above Mach 1.

1.8.1 also contains a couple of minor fixes for AltosUI when analyzing saved data files.

Version 1.8 includes support for our new TeleBT v4.0 ground station, updates for data analysis in our ground station software and bug fixes in in the flight software for all our boards and ground station interfaces.

Version 1.7 includes support for our new TeleMini v3.0 flight computer and bug fixes in in the flight software for all our boards and ground station interfaces.

Version 1.6.8 fixes a TeleMega and TeleMetrum v2.0 bug where the device could stop logging data and transmitting telemetry in flight. All TeleMega v1.0, v2.0 and TeleMetrum v2.0 users should update their flight firmware.

Version 1.6.5 fixes a TeleMega and TeleMetrum v2.0 bug where the device would often stop logging data and transmitting telemetry in flight. All TeleMega v1.0, v2.0 and TeleMetrum v2.0 users should update their flight firmware.

Version 1.6.4 fixes a bluetooth communication problem with TeleBT v1.0 devices, along with some altosui and altosdroid minor nits. It also now ships firmware for some newer devices.

Version 1.6.3 adds idle mode to AltosDroid and has bug fixes for our host software on desktops, laptops an android devices along with BlueTooth support for Windows.

Version 1.6.2 includes support for our updated TeleMega v2.0 product and bug fixes in in the flight software for all our boards and ground station interfaces.