1 == Using Altus Metrum Hardware
3 Here are general instructions for hooking up an Altus Metrum
4 flight computer. Instructions specific to each model will be
5 found in the section devoted to that model below.
7 === Wiring and Electrical Interference
9 To prevent electrical interference from affecting the
10 operation of the flight computer, it's important to always
11 twist pairs of wires connected to the board. Twist the switch
12 leads, the pyro leads and the battery leads. This reduces
13 interference through a mechanism called common mode rejection.
15 === Hooking Up Lithium Polymer Batteries
17 All Altus Metrum flight computers have a two pin JST PH
18 series connector to connect up a single-cell Lithium Polymer
19 cell (3.7V nominal). You can purchase matching batteries
20 from the Altus Metrum store, or other vendors, or you can
21 make your own. Pin 1 of the connector is positive, pin 2 is
22 negative. Spark Fun sells a cable with the connector
23 attached, which they call a
24 link:https://www.sparkfun.com/products/9914[JST Jumper 2 Wire Assembly]
27 Many RC vendors also sell lithium polymer batteries with
28 this same connector. All that we have found use the opposite
29 polarity, and if you use them that way, you will damage or
30 destroy the flight computer.
32 === Hooking Up Pyro Charges
34 Altus Metrum flight computers always have two screws for
35 each pyro charge. This means you shouldn't need to put two
36 wires into a screw terminal or connect leads from pyro
37 charges together externally.
39 On the flight computer, one lead from each charge is hooked
40 to the positive battery terminal through the power switch.
41 The other lead is connected through the pyro circuit, which
42 is connected to the negative battery terminal when the pyro
45 === Hooking Up a Power Switch
47 Altus Metrum flight computers need an external power switch
48 to turn them on. This disconnects both the computer and the
49 pyro charges from the battery, preventing the charges from
50 firing when in the Off position. The switch is in-line with
51 the positive battery terminal.
53 === Understanding Beeps
55 Altus Metrum flight computers include a beeper to
56 provide information about the state of the system.
58 TeleMini doesn't have room for a beeper, so instead it
59 uses an LED, which works the same, except for every
60 beep is replaced with the flash of the LED.
63 Here's a short summary of all of the modes and the
65 ifdef::telemini[(or flashing, in the case of TeleMini v1)]
66 that accompanies each mode. In the description of the
67 beeping pattern, “dit” means a short beep while "dah"
68 means a long beep (three times as long). “Brap” means
69 a long dissonant tone.
72 [options="border",cols="1,1,2,2"]
81 |battery voltage in decivolts
82 |Calibrating sensors, detecting orientation.
87 |Ready to accept commands over USB
88 ifdef::radio[or radio link.]
93 |Waiting for launch. Not listening for commands.
98 |Accelerating upwards.
103 |Decelerating, but moving faster than 200m/s.
108 |Decelerating, moving slower than 200m/s
113 |Descending after apogee. Above main height.
118 |Descending. Below main height.
123 |Stable altitude for at least ten seconds.
129 |Error detected during sensor calibration.
132 Here's a summary of all of the Pad and Idle mode
133 indications. In Idle mode, you'll hear one of these
134 just once after the two short dits indicating idle
135 mode. In Pad mode, after the dit dah dah dit
136 indicating Pad mode, you'll hear these once every five
139 .Pad/Idle Indications
140 [options="header",cols="1,1,3"]
142 |Name |Beeps |Description
146 |No continuity detected on either apogee or main igniters.
150 |Continuity detected only on apogee igniter.
154 |Continuity detected only on main igniter.
159 |Continuity detected on both igniters.
164 |On-board data logging storage is full. This will
165 not prevent the flight computer from safely
166 controlling the flight or transmitting telemetry
167 signals, but no record of the flight will be
168 stored in on-board flash.
170 ifdef::easymega,telemega[]
172 |four very short beeps
173 |Continuity indication for the four additional pyro
174 channels on TeleMega and EasyMega. One high tone for
175 no continuity, one low tone for continuity. These are
176 produced after the continuity indicators for the two
177 primary igniter channels.
178 endif::easymega,telemega[]
183 For devices with a radio transmitter, in addition to
184 the digital and APRS telemetry signals, you can also
185 receive audio tones with a standard amateur
186 70cm FM receiver. While on the pad, you will hear
187 igniter status once every five seconds.
189 .Pad Radio Indications
190 [options="header",cols="1,1,3"]
192 |Name |Beeps |Description
196 |No continuity detected on either apogee or main igniters.
200 |Continuity detected only on apogee igniter.
204 |Continuity detected only on main igniter.
209 |Continuity detected on both igniters.
213 During ascent, the tones will be muted to allow the
214 telemetry data to consume the full radio bandwidth.
216 During descent and after landing, a ½ second tone will
217 be transmitted every five seconds. This can be used to
218 find the rocket using RDF techniques when the signal
219 is too weak to receive GPS information via telemetry
223 === Turning On the Power
225 Connect a battery and power switch and turn the switch
226 to "on". The flight computer will signal power on by
227 reporting the battery voltage and then perform an internal self
228 test and sensor calibration.
230 Once the self test and calibration are complete, there
231 are two modes that an Altus Metrum flight computer can
235 The flight computer is waiting to detect
236 launch and then fly the rocket. In this mode, the USB
238 ifdef::radio[disabled, and the radio goes into transmit-only mode.]
239 ifndef::radio[disabled.]
240 The only way to get out of this
241 mode is to power the flight computer down.
244 The flight computer is ready to communicate over USB
245 ifdef::radio[and in packet mode over the radio.]
247 the flight computer, download data or display
250 ifdef::telemetrum,easymega,telemega[]
251 For flight computers with accelerometers (TeleMetrum,
252 EasyMega and TeleMega), the mode is selected by the
253 orientation of the board during the self test
254 interval. If the board is pointing upwards as if ready
255 to fly, it will enter Flight/Pad mode. Otherwise, it will
257 endif::telemetrum,easymega,telemega[]
260 For EasyMini, if the USB cable is connected to a
261 computer, it will enter Idle mode. Otherwise, it will
262 enter Flight/Pad mode.
266 For TeleMini v1.0, if a packet link is waiting to
267 connect when the device is powered on, it will enter
268 Idle mode, otherwise it will enter Flight/Pad mode.
271 You can see in <<_understanding_beeps>>
272 how to tell which mode the flight computer is in.
274 === Using an External Active Switch Circuit
276 You can use an active switch circuit, such as the
277 Featherweight Magnetic Switch, with any Altus Metrum
278 flight computer. These require three connections, one to
279 the battery, one to the positive power input on the flight
280 computer and one to ground. Find instructions on how to
281 hook these up for each flight computer below. Then follow
282 the instructions that come with your active switch to
285 === Using a Separate Pyro Battery
287 As mentioned above in <<_hooking_up_pyro_charges>>, one
288 lead for each of the pyro charges is connected through
289 the power switch directly to the positive battery
290 terminal. The other lead is connected to the pyro
291 circuit, which connects it to the negative battery
292 terminal when the pyro circuit is fired. The pyro
293 circuit on all of the flight computers is designed to
296 To use a separate pyro battery, connect the negative pyro
297 battery terminal to the flight computer ground terminal,
298 the positive battery terminal to the igniter and the other
299 igniter lead to the negative pyro terminal on the flight
300 computer. When the pyro channel fires, it will complete the
301 circuit between the negative pyro terminal and the ground
302 terminal, firing the igniter. Specific instructions on how
303 to hook this up for each flight computer will be found
304 in the section below for that flight computer.
306 === Using a Different Kind of Battery
309 ifdef::telemini[and TeleMini v2 are]
311 designed to use either a
312 lithium polymer battery or any other battery producing
313 between 4 and 12 volts, such as a rectangular 9V
316 ifdef::telemega,easymega,telemetrum[]
318 TeleMega, EasyMega and TeleMetrum are only designed to
319 operate off a single-cell Lithium Polymer battery and
320 cannot be used with any other kind. Connecting a
321 different kind of battery to any of these will destroy
323 endif::telemega,easymega,telemetrum[]