X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=blobdiff_plain;f=doc%2Fmicropeak.xsl;fp=doc%2Fmicropeak.xsl;h=0000000000000000000000000000000000000000;hp=dafe36820650fa73f87da3691e7af758d74d2621;hb=ce297f14ff54d230d01fb6dedaafca571e8b836b;hpb=9aed128dc0aab5d49e1b3264c864a6c3e929bffe diff --git a/doc/micropeak.xsl b/doc/micropeak.xsl deleted file mode 100644 index dafe3682..00000000 --- a/doc/micropeak.xsl +++ /dev/null @@ -1,736 +0,0 @@ - - - - MicroPeak Owner's Manual - A recording altimeter for hobby rocketry - - - Keith - Packard - - - 2014 - Bdale Garbee and Keith Packard - - - - - - - - - This document is released under the terms of the - - Creative Commons ShareAlike 3.0 - - license. - - - - - 0.1 - 29 October 2012 - - Initial release with preliminary hardware. - - - - 1.0 - 18 November 2012 - - Updates for version 1.0 release. - - - - 1.1 - 12 December 2012 - - Add comments about EEPROM storage format and programming jig. - - - - 1.2 - 20 January 2013 - - Add documentation for the MicroPeak USB adapter board. Note - the switch to a Kalman filter for peak altitude - determination. - - - - 1.3.2 - 12 February 2014 - - Add a "Download" button to the main window, which makes it - quicker to access the download function. Update the data - download documentation to reflect the new MicroPeak USB - adapter design. Monitor data during download to let you see - if the USB connection is working at all by showing the - characters received from the MicroPeak USB adapter. - - - - - - Acknowledgements - - 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 - out on the rocket flight line somewhere. - -Bdale Garbee, KB0G -NAR #87103, TRA #12201 - -Keith Packard, KD7SQG -NAR #88757, TRA #12200 - - - - - Quick Start Guide - - MicroPeak is designed to be easy to use. Requiring no external - components, flying takes just a few steps - - - - - Install the battery. Fit a CR1025 battery into the plastic - carrier. The positive (+) terminal should be towards the more - open side of the carrier. Slip the carrier into the battery - holder with the positive (+) terminal facing away from the - circuit board. - - - - - - - - - - - - Install MicroPeak in your rocket. This can be as simple as - preparing a soft cushion of wadding inside a vented model payload - bay. Wherever you mount it, make sure you protect the - barometric sensor from corrosive ejection gasses as those - will damage the sensor, and shield it from light as that can - cause incorrect sensor readings. - - - - - Turn MicroPeak on. Slide the switch so that the actuator - covers the '1' printed on the board. MicroPeak will report - the maximum height of the last flight in decimeters using a - sequence of flashes on the LED. A sequence of short flashes - indicates one digit. A single long flash indicates zero. The - height is reported in decimeters, so the last digit will be - tenths of a meter. For example, if MicroPeak reports 5 4 4 - 3, then the maximum height of the last flight was 544.3m, or - 1786 feet. - - - - - Finish preparing the rocket for flight. After the - previous flight data have been reported, MicroPeak waits for - one minute before starting to check for launch. This gives - you time to finish assembling the rocket. As those - activities might cause pressure changes inside the airframe, - MicroPeak might accidentally detect boost. If you need to do - anything to the airframe after the one minute window passes, - make sure to be careful not to disturb the altimeter. The - LED will remain dark during the one minute delay, but after - that, it will start blinking once every 3 seconds. - - - - - Fly the rocket. Once the rocket passes about 30m in height - (100 feet), the micro-controller will record the ground - pressure and track the pressure seen during the flight. In - this mode, the LED flickers rapidly. When the rocket lands, - and the pressure stabilizes, the micro-controller will record - the minimum pressure pressure experienced during the flight, - compute the height represented by the difference in air - pressure and blink that value out on the LED. After that, - MicroPeak powers down to conserve battery power. - - - - - 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. - - - - - - Handling Precautions - - 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 - devices, there are some precautions you must take. - - - The CR1025 Lithium batteries have an - extraordinary power density. This is great because we can fly with - much less battery mass... but if they are punctured - or their contacts are allowed to short, they can and will release their - energy very rapidly! - Thus we recommend that you take some care when handling MicroPeak - to keep conductive material from coming in contact with the exposed metal elements. - - - The barometric sensor used in MicroPeak is sensitive to - sunlight. Please consider this when designing an - installation. Many model rockets with payload bays use clear - plastic for the payload bay. Replacing these with an opaque - cardboard tube, painting them, or wrapping them with a layer of - masking tape are all reasonable approaches to keep the sensor - out of direct sunlight. - - - The barometric sensor sampling ports must be able to "breathe", - both by not being covered by foam or tape or other materials that might - directly block the hole on the top of the sensor, and also by having a - suitable static vent to outside air. - - - As with all other rocketry electronics, Altus Metrum altimeters must - be protected from exposure to corrosive motor exhaust and ejection - charge gasses. - - - - The MicroPeak USB adapter - - - - - - - - - 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. - -
- Installing the MicroPeak software - - The MicroPeak application runs on Linux, Mac OS X and - Windows. You can download the latest version from - . - - - On Mac OS X and Windows, the FTDI USB device driver needs to - be installed. A compatible version of this driver is included - with the MicroPeak application, but you may want to download a - newer version from . - -
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- Downloading Micro Peak data - - - - Plug the MicroPeak USB adapter in to your computer. - - - - - - Start the MicroPeak application. - - - - - - - - - - - - - Click on the Download button at the top of the window. - - - - - - - - - - - - - Select from the listed devices. There will probably be - only one. - - - - - - - - - - - - The application will now wait until it receives valid data - from the MicroPeak USB adapter. - - - - - - - - - - The MicroPeak USB adapter has a small phototransistor - under the hole in the center of the box. - Locate this, turn on the MicroPeak and place the orange LED on the MicroPeak - directly inside the hole, resting the MicroPeak itself on - the box. You should see the blue LED on the MicroPeak USB - adapter blinking in time with the orange LED on the - MicroPeak board itself. - - - - - - - - - - - - - After the maximum flight height is reported, MicroPeak will - pause for a few seconds, blink the LED four times rapidly - and then send the data in one long blur on the LED. The - MicroPeak application should receive the data. When it does, - 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. - - - - - - - - - - - - - Once the data are saved, a graph will be displayed with - height, speed and acceleration values computed from the - recorded barometric pressure data. See the next section - for more details on that. - - - -
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- Analyzing MicroPeak Data - - The MicroPeak application can present flight data in the form - of a graph, a collection of computed statistics or in tabular - form. - - - MicroPeak collects raw barometric pressure data which is - then used to compute the remaining data. Altitude is computed - through a standard atmospheric model. Absolute error in this - data will be affected by local atmospheric - conditions. Fortunately, these errors tend to mostly cancel - out, so the error in the height computation is much smaller - than the error in altitude would be. - - - Speed and acceleration are computed by first smoothing the - height data with a Gaussian window averaging filter. For speed - data, this average uses seven samples. For acceleration data, - eleven samples are used. These were chosen to provide - reasonably smooth speed and acceleration data, which would - otherwise be swamped with noise. - - - The File menu has operations to open existing flight logs, - Download new data from MicroPeak, Save a copy of the flight - log to a new file, Export the tabular data (as seen in the Raw - Data tab) to a file, change the application Preferences, Close - the current window or close all windows and Exit the - application. - -
- MicroPeak Graphs - - Under the Graph tab, the height, speed and acceleration values - are displayed together. You can zoom in on the graph by - clicking and dragging to sweep out an area of - interest. Right-click on the plot to bring up a menu that will - let you save, copy or print the graph. - - - - - - - - -
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- MicroPeak Flight Statistics - - The Statistics tab presents overall data from the flight. Note - that the Maximum height value is taken from the minumum - pressure captured in flight, and may be different from the - apparant apogee value as the on-board data are sampled twice - as fast as the recorded values, or because the true apogee - occurred after the on-board memory was full. Each value is - presented in several units as appropriate. - - - - - - - - -
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- Raw Data - - A table consisting of the both the raw barometric pressure - data and values computed from that for each recorded time. - - - - - - - - -
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- Configuring the Graph - - This selects which graph elements to show, and lets you - switch between metric and imperial units - - - - - - - - -
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- Setting MicroPeak Preferences - - - - - - - - - The MicroPeak application has a few user settings which are - configured through the Preferences dialog, which can be - accessed from the File menu. - - - - The Log Directory is where flight data will be saved to - and loaded from by default. Of course, you can always - navigate to other directories in the file chooser windows, - this setting is just the starting point. - - - - - If you prefer to see your graph data in feet and - miles per hour instead of meters and meters per second, - you can select Imperial Units. - - - - - To see what data is actually arriving over the serial - port, start the MicroPeak application from a command - prompt and select the Serial Debug option. This can be - useful in debugging serial communication problems, but - most people need never choose this. - - - - - You can adjust the size of the text in the Statistics tab - by changing the Font size preference. There are three - settings, with luck one will both fit on your screen and - provide readable values. - - - - - The Look & feel menu shows a list of available - application appearance choices. By default, the MicroPeak - application tries to blend in with other applications, but - you may choose some other appearance if you like. - - - - - - 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. - -
- - - Technical Information -
- Barometric Sensor - - 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. - - - The pressure range corresponds roughly to an altitude range of - -1500m (-4900 feet) to 31000m (102000 feet), while the - resolution is approximately 20cm (8 inches) near sea level and - 60cm (24in) at 10000m (33000 feet). - - - Ground pressure is computed from an average of 16 samples, - taken while the altimeter is at rest. The flight pressure used to - report maximum height is computed from a Kalman filter - designed to smooth out any minor noise in the sensor - values. The flight pressure recorded to non-volatile storage - is unfiltered, coming directly from the pressure sensor. - -
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- Micro-controller - - 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 - storage of previous flight data. - - - The ATtiny85 has a low-power mode which turns off all of the - clocks and powers down most of the internal components. In - this mode, the chip consumes only .1μA of power. MicroPeak - uses this mode once the flight has ended to preserve battery - power. - -
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- Lithium Battery - - 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 - sitting on the launch pad or during flight. - - - The large positive terminal (+) is usually marked, while the - smaller negative terminal is not. Make sure you install the - battery with the positive terminal facing away from the - circuit board where it will be in contact with the metal - battery holder. A small pad on the circuit board makes contact - with the negative battery terminal. - - - Shipping restrictions may prevent us from including a CR1025 - battery with MicroPeak. If so, many stores carry CR1025 - batteries as they are commonly used in small electronic - devices such as flash lights. - -
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- Atmospheric Model - - 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 - which is then used to compute the altitude of the ground and - apogee. The difference between these represents the maximum - height of the flight. - - - The model assumes a particular set of atmospheric conditions, - which, while a reasonable average, cannot represent the changing - nature of the real atmosphere. Fortunately, for flights - reasonably close to the ground, the effect of this global - inaccuracy are largely canceled out when the computed ground - altitude is subtracted from the computed apogee altitude, so - the resulting height is more accurate than either the ground - or apogee altitudes. - - - Because the raw pressure data is recorded to non-volatile - storage, you can use that, along with a more sophisticated - atmospheric model, to compute your own altitude values. - -
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- Mechanical Considerations - - 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 - ruggedness. - - - The MicroPeak battery holder is designed to withstand impact - up to 150g without breaking contact (or, worse yet, causing - the battery to fall out). That means it should stand up to - almost any launch you care to try, and should withstand fairly - rough landings. - - - The power switch is designed to withstand up to 50g forces in - 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. - -
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- On-board data storage - - 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 - flight. Barometric measurements from the ground before launch - and at apogee are stored, and used at power-on to compute the - height of the last flight. - - - In addition to the data used to present the height of the last - flight, MicroPeak also stores barometric information sampled - at regular intervals during the flight. This is the - information captured with the MicroPeak USB adapter. It can - also be read from MicroPeak through any AVR programming - tool. - - - 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 - from the previous sample, assuming that pressure doesn't - change by more more than 32kPa in a single sample - interval. Note that this pressure data is not - filtered in any way, while both the recorded ground and apogee - pressure values are, so you shouldn't expect the minimum - instantaneous pressure value to match the recorded minimum - pressure value exactly. - - - MicroPeak samples pressure every 96ms, but stores only every - other sample in the EEPROM. This provides for 251 pressure - samples at 192ms intervals, or 48.192s of storage. The clock - used for these samples is a factory calibrated RC circuit - built into the ATtiny85 and is accurate only to within ±10% at - 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. - -
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- MicroPeak Programming Interface - - MicroPeak exposes a standard 6-pin AVR programming interface, - but not using the usual 2x3 array of pins on 0.1" - centers. Instead, there is a single row of tiny 0.60mm × - 0.85mm pads on 1.20mm centers exposed near the edge of the - circuit board. We couldn't find any connector that was - small enough to include on the circuit board. - - - In lieu of an actual connector, the easiest way to connect to - the bare pads is through a set of Pogo pins. These - spring-loaded contacts are designed to connect in precisely - this way. We've designed a programming jig, the MicroPeak - Pogo Pin board which provides a standard AVR interface on one - end and a recessed slot for MicroPeak to align the board with - the Pogo Pins. - - - The MicroPeak Pogo Pin board is not a complete AVR programmer, - it is an interface board that provides a 3.3V regulated power - supply to run the MicroPeak via USB and a standard 6-pin AVR - programming interface with the usual 2x3 grid of pins on 0.1" - centers. This can be connected to any AVR programming - dongle. - - - The AVR programming interface cannot run faster than ¼ of the - AVR CPU clock frequency. Because MicroPeak runs at 250kHz to - save power, you must configure your AVR programming system to - clock the AVR programming interface at no faster than - 62.5kHz, or a clock period of 32µS. - -
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