Copyright © 2012 Bdale Garbee and Keith Packard
+
Copyright © 2012 Bdale Garbee and Keith Packard
This document is released under the terms of the Creative Commons ShareAlike 3.0 @@ -14,7 +14,7 @@ Add documentation for the MicroPeak USB adapter board. Note the switch to a Kalman filter for peak altitude determination. -
Thanks to John Lyngdal for suggesting that we build something like this.
Have fun using these products, and we hope to meet all of you
@@ -26,7 +26,7 @@ NAR
Keith Packard, KD7SQG
NAR #88757, TRA #12200
-
Table of Contents
List of Tables
Table of Contents
List of Tables
MicroPeak is designed to be easy to use. Requiring no external components, flying takes just a few steps
@@ -77,7 +77,7 @@ NAR Recover the data. Turn MicroPeak off and then back on. MicroPeak will blink out the maximum height for the last flight. Turn MicroPeak back off to conserve battery power. -
All Altus Metrum products are sophisticated electronic devices. When handled gently and properly installed in an air-frame, they will deliver impressive results. However, as with all electronic @@ -107,12 +107,12 @@ NAR As with all other rocketry electronics, Altus Metrum altimeters must be protected from exposure to corrosive motor exhaust and ejection charge gasses. -
Table of Contents
+
Table of Contents
MicroPeak stores barometric pressure information for the first 48 seconds of the flight in on-board non-volatile memory. The contents of this memory can be downloaded to a computer using the MicroPeak USB adapter. -
+
The MicroPeak application runs on Linux, Mac OS X and Windows. You can download the latest version from http://altusmetrum.org/AltOS. @@ -121,7 +121,7 @@ NAR be installed. A compatible version of this driver is included with the MicroPeak application, but you may want to download a newer version from http://www.ftdichip.com/FTDrivers.htm. -
+
Connect the MicroPeak USB adapter to a USB cable and plug it in to your computer.
@@ -147,7 +147,7 @@ NAR it will present the data in a graph and offer to save the data to a file. If not, you can power cycle the MicroPeak board and try again. -
The MicroPeak application can present flight data in the form of a graph, a collection of computed statistics or in tabular form. @@ -190,7 +190,7 @@ NAR Data tab) to a file, change the application Preferences, Close the current window or close all windows and Exit the application. -
The MicroPeak application has a few user settings which are configured through the Preferences dialog, which can be accessed from the File menu. @@ -224,7 +224,7 @@ NAR Note that MicroPeak shares a subset of the AltosUI preferences, so if you use both of these applications, change in one application will affect the other. -
Table of Contents
Table of Contents
MicroPeak uses the Measurement Specialties MS5607 sensor. This has a range of 120kPa to 1kPa with an absolute accuracy of 150Pa and a resolution of 2.4Pa. @@ -238,7 +238,7 @@ NAR taken while the altimeter is at rest. Flight pressure is computed from a Kalman filter designed to smooth out any minor noise in the sensor values. -
MicroPeak uses an Atmel ATtiny85 micro-controller. This tiny CPU contains 8kB of flash for the application, 512B of RAM for temporary data storage and 512B of EEPROM for non-volatile @@ -249,7 +249,7 @@ NAR this mode, the chip consumes only .1μA of power. MicroPeak uses this mode once the flight has ended to preserve battery power. -
The CR1025 battery used by MicroPeak holds 30mAh of power, which is sufficient to run for over 40 hours. Because MicroPeak powers down on landing, run time includes only time @@ -266,7 +266,7 @@ NAR battery with MicroPeak. If so, many stores carry CR1025 batteries as they are commonly used in small electronic devices such as flash lights. -
MicroPeak contains a fixed atmospheric model which is used to convert barometric pressure into altitude. The model was converted into a 469-element piece wise linear approximation @@ -282,7 +282,7 @@ NAR altitude is subtracted from the computed apogee altitude, so the resulting height is more accurate than either the ground or apogee altitudes. -
MicroPeak is designed to be rugged enough for typical rocketry applications. It contains two moving parts, the battery holder and the power switch, which were selected for their @@ -298,7 +298,7 @@ NAR any direction. Because it is a sliding switch, orienting the switch perpendicular to the direction of rocket travel will serve to further protect the switch from launch forces. -
The ATtiny85 has 512 bytes of non-volatile storage, separate from the code storage memory. The MicroPeak firmware uses this to store information about the last completed @@ -311,7 +311,7 @@ NAR at regular intervals during the flight. This information can be extracted from MicroPeak through any AVR programming tool. -
Table 4.1. MicroPeak EEPROM Data Storage
| Address | Size (bytes) | Description |
|---|---|---|
| 0x000 | 4 | Average ground pressure (Pa) |
| 0x004 | 4 | Minimum flight pressure (Pa) |
| 0x008 | 2 | Number of in-flight samples |
| 0x00a … 0x1fe | 2 | Instantaneous flight pressure (Pa) low 16 bits |
+
Table 4.1. MicroPeak EEPROM Data Storage
| Address | Size (bytes) | Description |
|---|---|---|
| 0x000 | 4 | Average ground pressure (Pa) |
| 0x004 | 4 | Minimum flight pressure (Pa) |
| 0x008 | 2 | Number of in-flight samples |
| 0x00a … 0x1fe | 2 | Instantaneous flight pressure (Pa) low 16 bits |
All EEPROM data are stored least-significant byte first. The instantaneous flight pressure data are stored without the upper 16 bits of data. The upper bits can be reconstructed @@ -331,7 +331,7 @@ NAR 25°C. So, you can count on the pressure data being accurate, but speed or acceleration data computed from this will be limited by the accuracy of this clock. -