Neil Anderson Flies EasyMega to 118k' At BALLS 23

Altus Metrum would like to congratulate Neil Anderson and Steve Cutonilli on the success the two stage rocket, “A Money Pit”, which flew on Saturday the 20th of September on an N5800 booster followed by an N1560 sustainer.

“A Money Pit” used two Altus Metrum EasyMega flight computers in the sustainer, each one configured to light the sustainer motor and deploy the drogue and main parachutes.

Safely Staged After a 7 Second Coast

After the booster burned out, the rocket coasted for 7 seconds to 250m/s, at which point EasyMega was programmed to light the sustainer. As a back-up, a timer was set to light the sustainer 8 seconds after the booster burn-out. In both cases, the sustainer ignition would have been inhibited if the rocket had tilted more than 20° from vertical. During the coast, the rocket flew from 736m to 3151m, with speed going from 422m/s down to 250m/s.

This long coast, made safe by EasyMega's quaternion-based tilt sensor, allowed this flight to reach a spectacular altitude.

Apogee Determined by Accelerometer

Above 100k', the MS5607 barometric sensor is out of range. However, as you can see from the graph, the barometric sensor continued to return useful data. EasyMega doesn't expect that to work, and automatically switched to accelerometer-only apogee determination mode.

Because off-vertical flight will under-estimate the time to apogee when using only an accelerometer, the EasyMega boards were programmed to wait for 10 seconds after apogee before deploying the drogue parachute. That turned out to be just about right; the graph shows the barometric data leveling off right as the apogee charges fired.

Fast Descent in Thin Air

Even with the drogue safely fired at apogee, the descent rate rose to over 200m/s in the rarefied air of the upper atmosphere. With increasing air density, the airframe slowed to 30m/s when the main parachute charge fired at 2000m. The larger main chute slowed the descent further to about 16m/s for landing.

Posted Mon 22 Sep 2014 09:33:01 PM PDT Tags: tags/rockets

AltOS 1.5 — EasyMega support, features and bug fixes

Bdale and I are pleased to announce the release of AltOS version 1.5.

AltOS is the core of the software for all of the Altus Metrum products. It consists of firmware for our cc1111, STM32L151, LPC11U14 and ATtiny85 based electronics and Java-based ground station software.

This is a major release of AltOS, including support for our new EasyMega board and a host of new features and bug fixes

AltOS Firmware — EasyMega added, new features and fixes

Our new flight computer, EasyMega, is a TeleMega without any radios:

  • 9 DoF IMU (3 axis accelerometer, 3 axis gyroscope, 3 axis compass).

  • Orientation tracking using the gyroscopes (and quaternions, which are lots of fun!)

  • Four fully-programmable pyro channels, in addition to the usual apogee and main channels.

AltOS Changes

We've made a few improvements in the firmware:

  • The APRS secondary station identifier (SSID) is now configurable by the user. By default, it is set to the last digit of the serial number.

  • Continuity of the four programmable pyro channels on EasyMega and TeleMega is now indicated via the beeper. Four tones are sent out after the continuity indication for the apogee and main channels with high tones indicating continuity and low tones indicating an open circuit.

  • Configurable telemetry data rates. You can now select among 38400 (the previous value, and still the default), 9600 or 2400 bps. To take advantage of this, you'll need to reflash your TeleDongle or TeleBT.

AltOS Bug Fixes

We also fixed a few bugs in the firmware:

  • TeleGPS had separate flight logs, one for each time the unit was turned on. Turning the unit on to test stuff and turning it back off would consume one of the flight log 'slots' on the board; once all of the slots were full, no further logging would take place. Now, TeleGPS appends new data to an existing single log.

  • Increase the maximum computed altitude from 32767m to 2147483647m. Back when TeleMetrum v1.0 was designed, we never dreamed we'd be flying to 100k' or more. Now that's surprisingly common, and so we've increased the size of the altitude data values to fit modern rocketry needs.

  • Continuously evaluate pyro firing condition during delay period. The previous firmware would evaluate the pyro firing requirements, and once met, would delay by the indicated amount and then fire the channel. If the conditions had changed state, the channel would still fire. Now, the conditions are continuously evaluated during the delay period and if they change state, the event is suppressed.

  • Allow negative values in the pyro configuration. Now you can select a negative speed to indicate a descent rate or a negative acceleration value to indicate acceleration towards the ground.

AltosUI and TeleGPS — EasyMega support, OS integration and more

The AltosUI and TeleGPS applications have a few changes for this release:

  • EasyMega support. That was a simple matter of adapting the existing TeleMega support.

  • Added icons for our file types, and hooked up the file manager so that AltosUI, TeleGPS and/or MicroPeak are used to view any of our data files.

  • Configuration support for APRS SSIDs, and telemetry data rates.

Posted Sat 13 Sep 2014 11:47:42 AM PDT Tags: tags/rockets

AltOS 1.4.1 — Fix ups for 1.4

Bdale and I are pleased to announce the release of AltOS version 1.4.1.

AltOS is the core of the software for all of the Altus Metrum products. It consists of firmware for our cc1111, STM32L151, LPC11U14 and ATtiny85 based electronics and Java-based ground station software.

This is a minor release of AltOS, incorporating a small handful of build and install issues. No new features have been added, and the only firmware change was to make sure that updated TeleMetrum v2.0 firmware is included in this release.

AltOS — TeleMetrum v2.0 firmware included

AltOS version 1.4 shipped without updated firmware for TeleMetrum v2.0. There are a couple of useful new features and bug fixes in that version, so if you have a TeleMetrum v2.0 board with older firmware, you should download this release and update it.

AltosUI and TeleGPS — Signed Windows Drivers, faster maps downloading

We finally figured out how to get our Windows drivers signed making it easier for Windows 7 and 8 users to install our software and use our devices.

Also for Windows users, we've fixed the Java version detection so that if you have Java 8 already installed, AltOS and TeleGPS won't try to download Java 7 and install that. We also fixed the Java download path so that if you have no Java installed, we'll download a working version of Java 6 instead of using an invalid Java 7 download URL.

Finally, for everyone, we fixed maps downloading to use the authorized Google API key method for getting map tiles. This makes map downloading faster and more reliable.

Thanks for flying with Altus Metrum!

Posted Tue 24 Jun 2014 10:35:08 PM PDT Tags: tags/rockets

TeleGPS Battery Life

I charged up one of the "160mAh" batteries that we sell. (The ones we've got now are labeled 200mAh; the 160mAh rating is something like a minimum that we expect to be able to ever get at that size.)

I connected the battery to a TeleGPS board, hooked up a telemetry monitoring setup on my laptop and set the device in the window of my office. This let me watch the battery voltage through the day without interrupting my other work. Of course, because the telemetry was logged to a file, I've now got a complete plot of the voltage data:

It looks like a pretty typical lithium polymer discharge graph; slightly faster drop from the 4.1V full charge voltage down to about 3.9V, then a gradual drop to 3.65 at which point it starts to dive as the battery is nearly discharged.

Because we run the electronics at 3.3V, and the LDO has a dropout of about 100mV, it's best if the battery stays above 3.4V. That occurred at around 21500 seconds of run time, or almost exactly six hours.

We also have an "850mAh" battery in the shop; I'd expect that to last a bit more than four times as long, or about a day. Maybe I'll get bored enough at some point to hook one up and verify that guess.

Posted Tue 17 Jun 2014 07:23:49 PM PDT Tags: tags/rockets

AltOS 1.4 — TeleGPS support, features and bug fixes

Bdale and I are pleased to announce the release of AltOS version 1.4.

AltOS is the core of the software for all of the Altus Metrum products. It consists of firmware for our cc1111, STM32L151, LPC11U14 and ATtiny85 based electronics and Java-based ground station software.

This is a major release of AltOS, including support for our new TeleGPS board and a host of new features and bug fixes

AltOS Firmware — TeleGPS added, new features and fixes

Our new tracker, TeleGPS, works quite differently than a flight computer

  • Starts tracking and logging at power-on

  • Disables RF and logging only when connected to USB

  • Doesn't log position when it isn't moving for a long time.

TeleGPS transmits our digital telemetry protocol, APRS and radio direction finding beacons.

For TeleMega, we've made the firing time for the additional pyro channels (A-D) configurable, in case the default (50ms) isn't long enough.

AltOS Beeping Changes

The three-beep startup tones have been replaced with a report of the current battery voltage. This is nice on all of the board, but particularly useful with EasyMini which doesn't have the benefit of telemetry reporting its state.

We also changed the other state tones to "Farnsworth" spacing. This makes them all faster, and easier to distinguish from the numeric reports of voltage and altitude.

Finally, we've added the ability to change the frequency of the beeper tones. This is nice when you have two Altus Metrum flight computers in the same ebay and want to be able to tell the beeps apart.

AltOS Bug Fixes

Fixed a bug which prevented you from using TeleMega's extra pyro channel 'Flight State After' configuration value.

AltOS 1.3.2 on TeleMetrum v2.0 and TeleMega would reset the flight number to 2 after erasing flights; that's been fixed.

AltosUI — New Maps, igniter tab and a few fixes

With TeleGPS tracks now potentially ranging over a much wider area than a typical rocket flight, the Maps interface has been updated to include zooming and multiple map styles. It also now uses less memory, which should make it work on a wider range of systems.

For TeleMega, we've added an 'Igniter' tab to the flight monitor interface so you can check voltages on the extra pyro channels before pushing the button.

We're hoping that the new Maps interface will load and run on machines with limited memory for Java applications; please let us know if this changes anything for you.

TeleGPS — All new application just for TeleGPS

While TeleGPS shares the same telemetry and data logging capabilities as all of the Altus Metrum flight computers, its use as a tracker is expected to be both broader and simpler than the rocketry-specific systems. We've build a custom TeleGPS application that incorporates the mapping and data visualization aspects of AltosUI, but eliminates all of the rocketry-specific flight state tracking.

Posted Sun 15 Jun 2014 07:48:15 PM PDT Tags: tags/rockets

Java Sound on Linux

I'm often in the position of having my favorite Java program (AltosUI) unable to make any sounds. Here's a history of the various adventures I've had.

Java and PulseAudio ALSA support

When we started playing with Java a few years ago, we discovered that if PulseAudio were enabled, Java wouldn't make any sound. Presumably, that was because the ALSA emulation layer offered by PulseAudio wasn't capable of supporting Java.

The fix for that was to make sure pulseaudio would never run. That's harder than it seems; pulseaudio is like the living dead; rising from the grave every time you kill it. As it's nearly impossible to install any desktop applications without gaining a bogus dependency on pulseaudio, the solution that works best is to make sure dpkg never manages to actually install the program with dpkg-divert:

# dpkg-divert --rename /usr/bin/pulseaudio

With this in place, Java was a happy camper for a long time.

Java and PulseAudio Native support

More recently, Java has apparently gained some native PulseAudio support in some fashion. Of course, I couldn't actually get it to work, even after running the PulseAudio daemon but some kind Debian developer decided that sound should be broken by default for all Java applications and selected the PulseAudio back-end in the Java audio configuration file.

Fixing that involved learning about said Java audio configuration file and then applying patch to revert the Debian packaging damage.

$ cat /usr/lib/jvm/java-7-openjdk-amd64/jre/lib/sound.properties
...
#javax.sound.sampled.Clip=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider
#javax.sound.sampled.Port=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider
#javax.sound.sampled.SourceDataLine=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider
#javax.sound.sampled.TargetDataLine=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider

javax.sound.sampled.Clip=com.sun.media.sound.DirectAudioDeviceProvider
javax.sound.sampled.Port=com.sun.media.sound.PortMixerProvider
javax.sound.sampled.SourceDataLine=com.sun.media.sound.DirectAudioDeviceProvider
javax.sound.sampled.TargetDataLine=com.sun.media.sound.DirectAudioDeviceProvider

You can see the PulseAudio mistakes at the top of that listing, with the corrected native interface settings at the bottom.

Java and single-open ALSA drivers

It used to be that ALSA drivers could support multiple applications having the device open at the same time. Those with hardware mixing would use that to merge the streams together; those without hardware mixing might do that in the kernel itself. While the latter is probably not a great plan, it did make ALSA a lot more friendly to users.

My new laptop is not friendly, and returns EBUSY when you try to open the PCM device more than once.

After downloading the jdk and alsa library sources, I figured out that Java was trying to open the PCM device multiple times when using the standard Java sound API in the simplest possible way. I thought I was going to have to fix Java, when I figured out that ALSA provides user-space mixing with the 'dmix' plugin. I enabled that on my machine and now all was well.

$ cat /etc/asound.conf
pcm.!default {
    type plug
    slave.pcm "dmixer"
}

pcm.dmixer  {
    type dmix
    ipc_key 1024
    slave {
        pcm "hw:1,0"
        period_time 0
        period_size 1024
        buffer_size 4096
        rate 44100
    }
    bindings {
        0 0
        1 1
    }
}

ctl.dmixer {
    type hw
    card 1
}

ctl.!default {
    type hw
    card 1
}

As you can see, my sound card is not number 0, it's number 1, so if your card is a different number, you'll have to adapt as necessary.

Posted Sat 05 Apr 2014 10:30:55 PM PDT Tags: tags/rockets

MicroPeak Approved for NAR Contests

The NAR Contest Board has approved MicroPeak for use in contests requiring a barometric altimeter starting on the 1st of April, 2014. You can read the announcement message on the contestRoc Yahoo message board here:

Contest Board Approves New Altimeter

The message was sent out on the 30th of January, but there is a 90 day waiting period after the announcement has been made before you can use MicroPeak in a contest, so the first date approved for contest flights is April 1. After that date, you should see MicroPeak appear in Appendix G of the pink book, which lists the altimeters approved for contest use

Thanks much to the NAR contest board and all of the fliers who helped get MicroPeak ready for this!

Posted Mon 17 Feb 2014 12:45:17 AM PST Tags: tags/rockets

AltOS 1.3.2 — Bug fixes and improved APRS support

Bdale and I are pleased to announce the release of AltOS version 1.3.2.

AltOS is the core of the software for all of the Altus Metrum products. It consists of firmware for our cc1111, STM32L151, LPC11U14 and ATtiny85 based electronics and Java-based ground station software.

This is a minor release of AltOS, including bug fixes for TeleMega, TeleMetrum v2.0 and AltosUI .

AltOS Firmware — GPS Satellite reporting and APRS improved

Firmware version 1.3.1 has a bug on TeleMega when it has data from more than 12 GPS satellites. This causes buffer overruns within the firmware. 1.3.2 limits the number of reported satellites to 12.

APRS now continues to send the last known good GPS position, and reports GPS lock status and number of sats in view in the APRS comment field, along with the battery and igniter voltages.

AltosUI — TeleMega GPS Satellite, GPS max height and Fire Igniters

AltosUI was crashing when TeleMega reported that it had data from more than 12 satellites. While the TeleMega firmware has been fixed to never do that, AltosUI also has a fix in case you fly a TeleMega board without updated firmware.

GPS max height is now displayed in the flight statistics. As the u-Blox GPS chips now provide accurate altitude information, we've added the maximum height as computed by GPS here.

Fire Igniters now uses the letters A through D to label the extra TeleMega pyro channels instead of the numbers 0-3.

Posted Sat 15 Feb 2014 02:45:39 AM PST Tags: tags/rockets

AltOS 1.3.1 — Bug fixes and improved APRS support

Bdale and I are pleased to announce the release of AltOS version 1.3.1.

AltOS is the core of the software for all of the Altus Metrum products. It consists of firmware for our cc1111, STM32L151, LPC11U14 and ATtiny85 based electronics and Java-based ground station software.

This is a minor release of AltOS, including bug fixes for TeleMega, TeleMetrum v2.0 and AltosUI .

AltOS Firmware — Antenna down fixed and APRS improved

Firmware version 1.3 has a bug in the support for operating the flight computer with the antenna facing downwards; the accelerometer calibration data would be incorrect. Furthermore, the accelerometer self-test routine would be confused if the flight computer were moved in the first second after power on. The firmware now simply re-tries the self-test several times.

I went out and bought a "real" APRS radio, the Yaesu FT1D to replace my venerable VX 7R. With this in hand, I changed our APRS support to use the compressed position format, which takes fewer bytes to send, offers increased resolution and includes altitude data. I took the altitude data out of the comment field and replaced that with battery and igniter voltages. This makes APRS reasonably useful in pad mode to monitor the state of the flight computer before boost.

Anyone with a TeleMega should update to the new firmware eventually, although there aren't any critical bug fixes here, unless you're trying to operate the device with the antenna pointing downwards.

AltosUI — TeleMega support and offline map loading improved.

I added all of the new TeleMega sensor data as possible elements in the graph. This lets you see roll rates and horizontal acceleration values for the whole flight. The 'Fire Igniter' dialog now lists all of the TeleMega extra pyro channels so you can play with those on the ground as well.

Our offline satellite images are downloaded from Google, but they restrict us to reading 50 images per minute. When we tried to download a 9x9 grid of images to save for later use on the flight line, Google would stop feeding us maps after the first 50. You'd have to poke the button a second time to try and fill in the missing images. We fixed this by just limiting how fast we load maps, and now we can reliably load an 11x11 grid of images.

Of course, there are also a few minor bug fixes, so it's probably worth updating even if the above issues don't affect you.

Posted Wed 22 Jan 2014 08:39:01 PM PST Tags: tags/rockets

AltOS 1.3 — TeleMega and EasyMini support

Bdale and I are pleased to announce the release of AltOS version 1.3.

AltOS is the core of the software for all of the Altus Metrum products. It consists of firmware for our cc1111, STM32L151, LPC11U14 and ATtiny85 based electronics and Java-based ground station software.

This is a major release of AltOS as it includes support for both of our brand new flight computers, TeleMega and EasyMini.

AltOS Firmware — New hardware, new features and fixes

Our new advanced flight computer, TeleMega, required a lot of new firmware features, including:

  • 9 DoF IMU (3 axis accelerometer, 3 axis gyroscope, 3 axis compass).

  • Orientation tracking using the gyroscopes (and quaternions, which are lots of fun!)

  • APRS support so your existing amateur radio receiver can track the location of your rocket.

  • Software FEC, both encoding and decoding.

  • Four fully-programmable pyro channels, in addition to the usual apogee and main channels.

  • STM32L CPU support. TeleMega needed a more powerful processor. The STM32L is a 32-bit ARM Cortex-M3 which is definitely up to the challenge.

Our new easy-to-use flight computer, EasyMini also uses a new processor, the LPC11U14, which is an ARM Cortex-M0 part.

For our existing cc1111 devices, there are some minor bug fixes for the flight software, so you should plan on re-flashing flight units at some point. However, there aren't any incompatible changes, so you don't have to do it all at once.

Bug fixes:

  • More USB fixes for Windows.

  • Turn off the cc1111 RC oscillator at startup. This may save a bit of power, and may reduce noise inside the chip a bit.

AltosUI — Redesigned for TeleMega and EasyMini support

AltosUI has also seen quite a bit of work for the 1.3 release, but almost all of that was a massive internal restructuring necessary to support flight computers with a wide range of sensors. From the user's perspective, it's pretty similar with a few changes:

  • Graphs can now show the raw barometric pressure

  • Support for TeleMega and EasyMini, including alternate TeleMega pyro channel configuration.

  • Bug fixes in how data were extracted from a flight record for graphing -- sometimes values would end up getting plotted out of order, causing weird jaggy lines.

Posted Thu 19 Dec 2013 02:22:57 AM PST Tags: tags/rockets