[web/altusmetrum] / TeleMetrum / index.mdwn

# TeleMetrum

This is a recording dual-deploy altimeter for high power model rocketry 
with integrated GPS and telemetry link.  

These are photos of our current version,
which includes an integrated GPS receiver and patch antenna:

<a href="v0.2/cimg5164-cropped.jpg"> <img src="v0.2/cimg5164-thumb.jpg"></a>
<a href="v0.2/cimg5171-cropped.jpg"> <img src="v0.2/cimg5171-thumb.jpg"></a>

And this is a photo of our original board with serial port for off-board GPS,
without the big off-board 1000uF cap from the original ejection circuit:

<a href="v0.1/loadedpair.jpg"> <img src="v0.1/loadedpair-thumb.jpg"></a>

## Motivation ##

Bdale and Keith both own 
[BeeLine](http://www.bigredbee.com/BeeLine.htm)
trackers from 
[Big Red Bee](http://www.bigredbee.com), and are pretty happy with them.
They use a PIC processor and a TI CC1050 transmitter chip, and
operate in the ham radio 70cm band.

One weekend while attending a conference together, we got to wondering if 
we couldn't adapt one to use as a downlink for the
[AltusMetrum](../AltusMetrum/) altimeter board in addition to direction
finding after flight.  That caused us to start thinking about other things
in the design we might want to tweak, and before long we were working on the
design of a new tracker board derived from the BeeLine design.
Another friend at the same conference showed us a board he was working on 
using a different part in the same TI series, that integrated a transceiver
and CPU on the same chip.
It didn't take us long to realize that with such a part we could combine and
simplify things by building a new altimeter with integrated RF link!  And
after gaining some experience in 2009 with a first version, we realized we
always want GPS on board, which lead to our current second generation boards.

## Features ##

### User View ###

* Recording altimeter for model rocketry
* Supports dual deployment (can fire 2 ejection charges)
* 70cm ham-band transceiver for telemetry downlink
* Barometric pressure sensor good to 45k feet MSL
* 1-axis high-g accelerometer for motor characterization
* On-board, integrated GPS receiver
* On-board non-volatile memory for flight data storage
* USB for power, configuration, and data recovery
* Integrated support for LiPo rechargeable batteries
* Uses LiPo to fire e-matches, optional support for separate pyro battery
* 2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube

### Developer View ###

* Hardware Features
        * [TI CC1111F32](http://focus.ti.com/docs/prod/folders/print/cc1111f32.html) Low Power RF System-on-Chip
                * Sub-1Ghz transceiver
                * 8051 MCU
                * 32k Flash
                * 4k RAM
                * USB 2.0
                * 6 12-bit analog inputs (11 bits with single-ended sensors)
                * 2 channels of serial I/O
                * digital I/O
        * [Atmel AT45DB081D](http://www.atmel.com/dyn/products/product_card.asp?part_id=3819) DataFlash memory
                * 1M x 8
                * 256 byte page size
                * SPI interface
                * other parts in this Atmel DataFlash series can optionally be used
        * [SkyTraq](http://www.skytraq.com.tw/) Venus634FLPx GPS receiver
                * on-board passive patch antenna
                * U.FL connector with 3.3V DC for optional external amplified antenna
                * async serial interface
        * [Freescale MP3H6115A](http://www.freescale.com/webapp/search.partparamdetail.framework?PART_NUMBER=MP3H6115A6U) pressure sensor
        * [Freescale MMA2202EG](http://www.freescale.com/webapp/search.partparamdetail.framework?PART_NUMBER=MMA2202EG) 50g accelerometer.  Can use 40-200g variants!
* Software Features
        * Written mostly in C with some 8051 assembler
        * Runs from on-chip flash, uses on-chip RAM, stores flight data to
                serial DataFlash chip
        * USB serial emulation for "console" interface
* Tools Used
        * [gEDA](http://www.gpleda.org/) for schematic capture and PCB layout
        * [SDCC](http://sdcc.sourceforge.net/) compiler and source debugger
* Licenses
        * The hardware is licensed under the [TAPR](http://www.tapr.org) [Open Hardware License](http://www.tapr.org/ohl.html)
        * The software is licensed [GPL version 2](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)

### v0.1 Differences  ###

* 2.5 x 1 inch board with all parts mounted on one side
* 4-pin PicoBlade serial port connector for attachment of external GPS module 
* USB connector projected approximately 3mm over the edge of the board
* Debug connector used 4 IC socket pins on 100 mil centers
* no companion board interface
* [Microchip 25LC1024](http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en520389) CMOS serial EEPROM instead of DataFlash
        * 128k x 8
        * SPI interface
* [Microchip MCP9700A](http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en027103) discrete temperature sensor
* used 1000uF electrolytic capacitor charged to 5V for pyro supply
* two LEDs instead of one attached to CPU

The elimination of the discrete temperature sensor and second LED were
necessary to support the companion board interface added in v0.2.

## [Production History](../production) ##

## [Flight Logs](flightlogs) ##

## Problems ##

* The CC1111F32 is a 36-pin QFN package, which necessitates reflow 
  soldering.  Since we needed to reflow solder anyway, and because TI used 
  them in their reference design, we went a little crazy and used 0402 
  passive parts everywhere.  That means working under a microscope to 
  place parts!  Without an inspection microscope, loading and testing these
  boards might be impossible.

* The addition of on-board GPS in v0.2 means that the total power consumption
  can exceed the rate at which we draw power from the USB interface, 
  particularly when the GPS is in cold start mode.  This means a battery must 
  be attached during operation, and also that the battery will only charge 
  effectively from USB when the board is turned off.

* The v0.1 artwork had three issues, two of which required physical rework
  on each board.  All of these issues were fixed in v0.2.

        * The USB connector footprint was placed wrong, so that the
          connector hung out over the edge of the board instead of being 
          flush.
        * We needed chip select on the SPI memory.  To fix that, we gave up the 
          ability to put the accelerometer into self-test mode and used that 
          GPIO line to pull chip select on the memory, which required two
          cuts and two jumpers.  
        * The igniter sense circuits each needed a second resistor to 
          complete the voltage divider so our 3.3V CPU ADC could read the 
          5V ejection voltage.  This was fixed by changing two resistor 
          values, and tacking two additional resistors onto the board
          with jumpers to ground.

## Artifacts ##

The hardware design current gEDA files are available from 
[git.gag.com](http://git.gag.com) in the project 
[hw/telemetrum](http://git.gag.com/?p=hw/telemetrum;a=summary).  

Work on the next version proceeds on the master branch, with occasional
temporary branches created when Bdale is making some major / speculative
change.  The 'v0.2' and 'v0.1' branches document what we're actually flying 
right now on the two respective PCB revisions.  The 'ground' branch has a 
cut-down schematic used to generate the BOM for partially loading v0.1 boards 
to used on the ground.  We call the on-the-ground version 'TeleDongle'.

For those who don't have ready access to the gEDA suite, here are pdf snapshots
of files in more easily readable form.  

* These are from the v0.2 branch:
 * [schematic](v0.2/telemetrum.pdf)
 * [pcb artwork](v0.2/telemetrum.pcb.pdf)
 * [bill of materials](v0.2/partslist.csv)
* These are as of the working-v0.1 tag:  
 * [schematic](v0.1/telemetrum.pdf)
 * [pcb artwork](v0.1/telemetrum.pcb.pdf)
 * [bill of materials](v0.1/telemetrum.bom)

Our [AltOS](../AltOS) firmware works well enough that we now routinely fly 
TeleMetrum with no backup.  Rockets with v0.1 boards have exceeded 50g 
acceleration, been above Mach 1, and reached altitudes greater 
than 12k feet AGL with great results.  Keith's ground station program 
called ao-view logs telemetry to disk, displays current and max values for 
key parameters during flight, and even includes voice synthesis 
during the flight so that our eyes can stay on the rockets!  We have post
flight analysis software that makes it easy to extract data from the board,
analyze it, and even generate KML files for viewing flights in GoogleEarth!
More details on the software, including full source code and pre-built packages
can be found on the [AltOS](../AltOS) page on this site.

## Future Plans ##

As of early February 2010, three prototypes of v0.2 are done and working on 
the bench.  We hope to flight test them shortly, then arrange a production
run in time to make TeleMetrum available in assembled and tested form to 
others in the rocketry hobby who have expressed interest in time for the 
2010 flying season.

Because we understand that not everyone uses Linux, we've started discussing 
the best way to make a cross-platform ground station program for use with 
[AltOS](../AltOS), perhaps in Java...