Stanford SSI Wiki - User contributions [en]

Vector Graphics in Altium

2017-02-08T22:03:27Z

Thomas: /* Using an existing logo */

Altium currently lacks well-integrated support for putting vector graphics onto the silkscreen. There are a couple of workarounds for this. SSI's preferred option for vector graphics that will be re-used is to add them to the SSI font.

For one-off's, there is the PCB Logo Importer Script provided by Altium and documented [http://wiki.altium.com/pages/viewpage.action?pageId=6848718 here] or in [http://letanphuc.net/2016/05/put-logo-pcb-altium/ more detail here].

== Using an existing logo ==

The SSI Altium libraries SVN includes an "SSI Logos" font that already contains most of the logos you might need (including SSI logos, team logos, and sponsor logos). You can find the font here:

https://subversion.assembla.com/svn/stanfordspaceinitiative/libraries/logos/SSI

Install the font by double-clicking and pressing Add or Install.

Then launch Altium and insert a String on the Top or Bottom Overlay layer. Select TrueType font and choose "SSI Logos" as the font.

Each logo corresponds to a particular character. For example, typing 'A' will insert the SSI Logo. You can find a full list of available graphics here:

https://stanfordssi.assembla.com/spaces/stanfordspaceinitiative/subversion/source/HEAD/libraries/logos/SSI/SSI_LogosKey.txt

== Adding a new SVG ==

Vector Graphics in Altium

2017-02-08T01:36:36Z

Thomas:

Vector Graphics in Altium

2017-02-08T01:36:11Z

Thomas: Created page with "Altium currently lacks well-integrated support for putting vector graphics onto the silkscreen. There are a couple of workarounds for this. SSI's preferred option for vector g..."

File:Altimeter.jpg

2016-02-20T08:05:52Z

Thomas:

SSI Altimeter

2016-02-20T08:04:52Z

Thomas:

The SSI Altimeter (also known as the "Dual Deploy Altimeter" or "Althometer") is an ongoing project to develop a low-cost, customization, and easily programmable altimeter for SSI-run rocketry certifications.

[[Category:Rockets]]

{{rocket-project
| header = SSI Altimeter
| img link = File:altimeter.jpg}}

== Project Status ==

The altimeter is currently under development. An revision 1 has been produced and is currently undergoing testing.

== Using the Altimeter ==

=== First Steps ===

Mount the Altimeter and a single-cell LiPo battery however you like in the rocket. Note that there must be a vent hole to the altimeter or else it cannot detect changes in pressure. (At this point, it is not orientation dependent, however this will eventually change.)

Before connecting the battery to the altimeter, go ahead and connect the deployment charges to the green terminal blocks. They are labelled on the bottom of the board. For the vast majority of applications, the polarity does not matter.

=== Power On ===

''The altimeter is very sensitive to wind. It works fine when inside of a rocket body, but it gets very confused when its sensor is directly exposed to the wind.'' For this reason, there is a delay before the altimeter starts doing anything. It's important that you get the altimeter installed in the body tube (or nose cose) before this delay expires.

When the altimeter powers up, you will see:
1. White LED blink
2. Program code blink (in this case: green / red)
3. White LED blink
4. Green LED - This green LED stays on during the startup delay.

By the time the green LED goes off, the altimeter should be in the body tube or otherwise shielded from the wind. The altimeter will also take this as its zero altitude reading, so you should be fairly close to the launch site elevation by now.

Miss it? No problem. Press the little button in the top left to reset to the beginning. As long as no charges fired, there's no problem with just resetting.

=== In Flight ===

For this launch, the altimeter is programmed to:
1. Wait until the rocket reaches at least 900 meters.
2. Keep waiting until the rocket has fallen at least 100 meters.
3. Deploy charge 1 after the rocket passes 700 meters.
4. Deploy charge 2 after the rocket passes 600 meters.

=== Recovery and Post-Flight ===

When you get the altimeter back, it should have a solid blue LED. If it doesn't, disconnect the (potentially undeployed) charges and note the color of the LED (and tell Thomas).

The (limited, in this case) data from the flight is only stored as long as the altimeter is on. So don't pull the battery yet!

Using an FTDI chip, connect GND on the FTDI to the debug pin nearest the LED (green lead in the photo below) and the RX pin on the FTDI to the debug pin nearest the logo (blue lead in the photo below). Open a serial terminal (screen /dev/ttyUSB0 on Linux - you can probably use Arduino if you're running an inferior OS). You should see a bunch of text output. It's just a repeating message, so you only need one copy of it.

[[File:altimeterserial.jpg|400px]]

== Random things ==

=== Programming Configuration ===

[[File:altimeterprog.jpg|400px]]

=== How to disconnect the LiPo ===

Hint: Don't pull on the wires!

[https://www.sparkfun.com/tutorials/241]

== Accessing Source Files ==

Source files for the altimeter are in SSI's Subversion repository (where all Altium files are hosted). If you are an SSI member, talk with Logan Herrera or Thomas Teisberg about getting access.

The intent is to make all of the hardware open source. This will likely be done after the project has reached a stable point.

SSI Altimeter

2016-02-20T08:02:03Z

Thomas:

The SSI Altimeter (also known as the "Dual Deploy Altimeter" or "Althometer") is an ongoing project to develop a low-cost, customization, and easily programmable altimeter for SSI-run rocketry certifications.

[[Category:Rockets]]

{{rocket-project
| header = SSI Altimeter
| img link = altimeter.jpg}}

== Project Status ==

The altimeter is currently under development. An revision 1 has been produced and is currently undergoing testing.

== Using the Altimeter ==

=== First Steps ===

Mount the Altimeter and a single-cell LiPo battery however you like in the rocket. Note that there must be a vent hole to the altimeter or else it cannot detect changes in pressure. (At this point, it is not orientation dependent, however this will eventually change.)

Before connecting the battery to the altimeter, go ahead and connect the deployment charges to the green terminal blocks. They are labelled on the bottom of the board. For the vast majority of applications, the polarity does not matter.

=== Power On ===

''The altimeter is very sensitive to wind. It works fine when inside of a rocket body, but it gets very confused when its sensor is directly exposed to the wind.'' For this reason, there is a delay before the altimeter starts doing anything. It's important that you get the altimeter installed in the body tube (or nose cose) before this delay expires.

When the altimeter powers up, you will see:
1. White LED blink
2. Program code blink (in this case: green / red)
3. White LED blink
4. Green LED - This green LED stays on during the startup delay.

By the time the green LED goes off, the altimeter should be in the body tube or otherwise shielded from the wind. The altimeter will also take this as its zero altitude reading, so you should be fairly close to the launch site elevation by now.

Miss it? No problem. Press the little button in the top left to reset to the beginning. As long as no charges fired, there's no problem with just resetting.

=== In Flight ===

For this launch, the altimeter is programmed to:
1. Wait until the rocket reaches at least 900 meters.
2. Keep waiting until the rocket has fallen at least 100 meters.
3. Deploy charge 1 after the rocket passes 700 meters.
4. Deploy charge 2 after the rocket passes 600 meters.

=== Recovery and Post-Flight ===

When you get the altimeter back, it should have a solid blue LED. If it doesn't, disconnect the (potentially undeployed) charges and note the color of the LED (and tell Thomas).

The (limited, in this case) data from the flight is only stored as long as the altimeter is on. So don't pull the battery yet!

Using an FTDI chip, connect GND on the FTDI to the debug pin nearest the LED (green lead in the photo below) and the RX pin on the FTDI to the debug pin nearest the logo (blue lead in the photo below). Open a serial terminal (screen /dev/ttyUSB0 on Linux - you can probably use Arduino if you're running an inferior OS). You should see a bunch of text output. It's just a repeating message, so you only need one copy of it.

[[File:altimeterserial.jpg|400px]]

== Random things ==

=== Programming Configuration ===

[[File:altimeterprog.jpg|400px]]

=== How to disconnect the LiPo ===

Hint: Don't pull on the wires!

[https://www.sparkfun.com/tutorials/241]

== Accessing Source Files ==

Source files for the altimeter are in SSI's Subversion repository (where all Altium files are hosted). If you are an SSI member, talk with Logan Herrera or Thomas Teisberg about getting access.

The intent is to make all of the hardware open source. This will likely be done after the project has reached a stable point.

SSI Altimeter

2016-02-20T08:01:35Z

Thomas:

The SSI Altimeter (also known as the "Dual Deploy Altimeter" or "Althometer") is an ongoing project to develop a low-cost, customization, and easily programmable altimeter for SSI-run rocketry certifications.

[[Category:Rockets]]

{{rocket-project
| header = SSI Altimeter
| img link = altimeter.jpg}}

== Project Status ==

The altimeter is currently under development. An revision 1 has been produced and is currently undergoing testing.

== Using the Altimeter ==

=== First Steps ===

Mount the Altimeter and a single-cell LiPo battery however you like in the rocket. Note that there must be a vent hole to the altimeter or else it cannot detect changes in pressure. (At this point, it is not orientation dependent, however this will eventually change.)

Before connecting the battery to the altimeter, go ahead and connect the deployment charges to the green terminal blocks. They are labelled on the bottom of the board. For the vast majority of applications, the polarity does not matter.

=== Power On ===

''The altimeter is very sensitive to wind. It works fine when inside of a rocket body, but it gets very confused when its sensor is directly exposed to the wind.'' For this reason, there is a delay before the altimeter starts doing anything. It's important that you get the altimeter installed in the body tube (or nose cose) before this delay expires.

When the altimeter powers up, you will see:
1. White LED blink
2. Program code blink (in this case: green / red)
3. White LED blink
4. Green LED - This green LED stays on during the startup delay.

By the time the green LED goes off, the altimeter should be in the body tube or otherwise shielded from the wind. The altimeter will also take this as its zero altitude reading, so you should be fairly close to the launch site elevation by now.

Miss it? No problem. Press the little button in the top left to reset to the beginning. As long as no charges fired, there's no problem with just resetting.

=== In Flight ===

For this launch, the altimeter is programmed to:
1. Wait until the rocket reaches at least 900 meters.
2. Keep waiting until the rocket has fallen at least 100 meters.
3. Deploy charge 1 after the rocket passes 700 meters.
4. Deploy charge 2 after the rocket passes 600 meters.

=== Recovery and Post-Flight ===

When you get the altimeter back, it should have a solid blue LED. If it doesn't, disconnect the (potentially undeployed) charges and note the color of the LED (and tell Thomas).

The (limited, in this case) data from the flight is only stored as long as the altimeter is on. So don't pull the battery yet!

Using an FTDI chip, connect GND on the FTDI to the debug pin nearest the LED (green lead in the photo below) and the RX pin on the FTDI to the debug pin nearest the logo (blue lead in the photo below). Open a serial terminal (screen /dev/ttyUSB0 on Linux - you can probably use Arduino if you're running an inferior OS). You should see a bunch of text output. It's just a repeating message, so you only need one copy of it.

[[File:altimeterserial.jpg|400px|thumb]]

== Random things ==

=== Programming Configuration ===

[[File:altimeterprog.jpg|400px|thumb]]

=== How to disconnect the LiPo ===

Hint: Don't pull on the wires!

[https://www.sparkfun.com/tutorials/241]

== Accessing Source Files ==

Source files for the altimeter are in SSI's Subversion repository (where all Altium files are hosted). If you are an SSI member, talk with Logan Herrera or Thomas Teisberg about getting access.

The intent is to make all of the hardware open source. This will likely be done after the project has reached a stable point.

File:Altimeterprog.jpg

2016-02-20T08:01:09Z

Thomas:

SSI Altimeter

2016-02-20T08:00:26Z

Thomas:

The SSI Altimeter (also known as the "Dual Deploy Altimeter" or "Althometer") is an ongoing project to develop a low-cost, customization, and easily programmable altimeter for SSI-run rocketry certifications.

[[Category:Rockets]]

{{rocket-project
| header = SSI Altimeter
| img link = altimeter.jpg}}

== Project Status ==

The altimeter is currently under development. An revision 1 has been produced and is currently undergoing testing.

== Using the Altimeter ==

=== First Steps ===

Mount the Altimeter and a single-cell LiPo battery however you like in the rocket. Note that there must be a vent hole to the altimeter or else it cannot detect changes in pressure. (At this point, it is not orientation dependent, however this will eventually change.)

Before connecting the battery to the altimeter, go ahead and connect the deployment charges to the green terminal blocks. They are labelled on the bottom of the board. For the vast majority of applications, the polarity does not matter.

=== Power On ===

''The altimeter is very sensitive to wind. It works fine when inside of a rocket body, but it gets very confused when its sensor is directly exposed to the wind.'' For this reason, there is a delay before the altimeter starts doing anything. It's important that you get the altimeter installed in the body tube (or nose cose) before this delay expires.

When the altimeter powers up, you will see:
1. White LED blink
2. Program code blink (in this case: green / red)
3. White LED blink
4. Green LED - This green LED stays on during the startup delay.

By the time the green LED goes off, the altimeter should be in the body tube or otherwise shielded from the wind. The altimeter will also take this as its zero altitude reading, so you should be fairly close to the launch site elevation by now.

Miss it? No problem. Press the little button in the top left to reset to the beginning. As long as no charges fired, there's no problem with just resetting.

=== In Flight ===

For this launch, the altimeter is programmed to:
1. Wait until the rocket reaches at least 900 meters.
2. Keep waiting until the rocket has fallen at least 100 meters.
3. Deploy charge 1 after the rocket passes 700 meters.
4. Deploy charge 2 after the rocket passes 600 meters.

=== Recovery and Post-Flight ===

When you get the altimeter back, it should have a solid blue LED. If it doesn't, disconnect the (potentially undeployed) charges and note the color of the LED (and tell Thomas).

The (limited, in this case) data from the flight is only stored as long as the altimeter is on. So don't pull the battery yet!

Using an FTDI chip, connect GND on the FTDI to the debug pin nearest the LED (green lead in the photo below) and the RX pin on the FTDI to the debug pin nearest the logo (blue lead in the photo below). Open a serial terminal (screen /dev/ttyUSB0 on Linux - you can probably use Arduino if you're running an inferior OS). You should see a bunch of text output. It's just a repeating message, so you only need one copy of it.

[[File:altimeterserial.jpg|400px|right|thumb]]

== Random things ==

=== Programming Configuration ===

[[File:altimeterprog.jpg|400px|right|thumb]]

=== How to disconnect the LiPo ===

Hint: Don't pull on the wires!

[https://www.sparkfun.com/tutorials/241]

== Accessing Source Files ==

Source files for the altimeter are in SSI's Subversion repository (where all Altium files are hosted). If you are an SSI member, talk with Logan Herrera or Thomas Teisberg about getting access.

The intent is to make all of the hardware open source. This will likely be done after the project has reached a stable point.

File:Altimeterserial.jpg

2016-02-20T07:57:47Z

Thomas:

SSI Altimeter

2016-02-20T07:54:50Z

Thomas:

The SSI Altimeter (also known as the "Dual Deploy Altimeter" or "Althometer") is an ongoing project to develop a low-cost, customization, and easily programmable altimeter for SSI-run rocketry certifications.

[[Category:Rockets]]

{{rocket-project
| header = SSI Altimeter
| img link = altimeter.jpg}}

== Project Status ==

The altimeter is currently under development. An revision 1 has been produced and is currently undergoing testing.

== Using the Altimeter ==

=== First Steps ===

Mount the Altimeter and a single-cell LiPo battery however you like in the rocket. Note that there must be a vent hole to the altimeter or else it cannot detect changes in pressure. (At this point, it is not orientation dependent, however this will eventually change.)

Before connecting the battery to the altimeter, go ahead and connect the deployment charges to the green terminal blocks. They are labelled on the bottom of the board. For the vast majority of applications, the polarity does not matter.

=== Power On ===

''The altimeter is very sensitive to wind. It works fine when inside of a rocket body, but it gets very confused when its sensor is directly exposed to the wind.'' For this reason, there is a delay before the altimeter starts doing anything. It's important that you get the altimeter installed in the body tube (or nose cose) before this delay expires.

When the altimeter powers up, you will see:
1. White LED blink
2. Program code blink (in this case: green / red)
3. White LED blink
4. Green LED - This green LED stays on during the startup delay.

By the time the green LED goes off, the altimeter should be in the body tube or otherwise shielded from the wind. The altimeter will also take this as its zero altitude reading, so you should be fairly close to the launch site elevation by now.

Miss it? No problem. Press the little button in the top left to reset to the beginning. As long as no charges fired, there's no problem with just resetting.

=== In Flight ===

For this launch, the altimeter is programmed to:
1. Wait until the rocket reaches at least 900 meters.
2. Keep waiting until the rocket has fallen at least 100 meters.
3. Deploy charge 1 after the rocket passes 700 meters.
4. Deploy charge 2 after the rocket passes 600 meters.

=== Recovery and Post-Flight ===

When you get the altimeter back, it should have a solid blue LED. If it doesn't, disconnect the (potentially undeployed) charges and note the color of the LED (and tell Thomas).

The (limited, in this case) data from the flight is only stored as long as the altimeter is on. So don't pull the battery yet!

Using an FTDI chip, connect GND on the FTDI to the debug pin nearest the LED (green lead in the photo below) and the RX pin on the FTDI to the debug pin nearest the logo (blue lead in the photo below). Open a serial terminal (screen /dev/ttyUSB0 on Linux - you can probably use Arduino if you're running an inferior OS). You should see a bunch of text output. It's just a repeating message, so you only need one copy of it.

[[File:altimeterserial.jpg]]

== Random things ==

=== Programming Configuration ===

[[File:altimeterprog.jpg]]

=== How to disconnect the LiPo ===

Hint: Don't pull on the wires!

[https://www.sparkfun.com/tutorials/241]

== Accessing Source Files ==

Source files for the altimeter are in SSI's Subversion repository (where all Altium files are hosted). If you are an SSI member, talk with Logan Herrera or Thomas Teisberg about getting access.

The intent is to make all of the hardware open source. This will likely be done after the project has reached a stable point.

SSI Altimeter

2016-02-20T07:50:25Z

Thomas:

The SSI Altimeter (also known as the "Dual Deploy Altimeter" or "Althometer") is an ongoing project to develop a low-cost, customization, and easily programmable altimeter for SSI-run rocketry certifications.

[[Category:Rockets]]

{{rocket-project
| header = SSI Altimeter
| img link =
| launch details = }}

== Project Status ==

The altimeter is currently under development. An revision 1 has been produced and is currently undergoing testing.

== Using the Altimeter ==

=== First Steps ===

Mount the Altimeter and a single-cell LiPo battery however you like in the rocket. Note that there must be a vent hole to the altimeter or else it cannot detect changes in pressure. (At this point, it is not orientation dependent, however this will eventually change.)

Before connecting the battery to the altimeter, go ahead and connect the deployment charges to the green terminal blocks. They are labelled on the bottom of the board. For the vast majority of applications, the polarity does not matter.

=== Power On ===

''The altimeter is very sensitive to wind. It works fine when inside of a rocket body, but it gets very confused when its sensor is directly exposed to the wind.'' For this reason, there is a delay before the altimeter starts doing anything. It's important that you get the altimeter installed in the body tube (or nose cose) before this delay expires.

When the altimeter powers up, you will see:
1. White LED blink
2. Program code blink (in this case: green / red)
3. White LED blink
4. Green LED - This green LED stays on during the startup delay.

By the time the green LED goes off, the altimeter should be in the body tube or otherwise shielded from the wind. The altimeter will also take this as its zero altitude reading, so you should be fairly close to the launch site elevation by now.

Miss it? No problem. Press the little button in the top left to reset to the beginning. As long as no charges fired, there's no problem with just resetting.

=== In Flight ===

For this launch, the altimeter is programmed to:
1. Wait until the rocket reaches at least 900 meters.
2. Keep waiting until the rocket has fallen at least 100 meters.
3. Deploy charge 1 after the rocket passes 700 meters.
4. Deploy charge 2 after the rocket passes 600 meters.

=== Recovery and Post-Flight ===

When you get the altimeter back, it should have a solid blue LED. If it doesn't, disconnect the (potentially undeployed) charges and note the color of the LED (and tell Thomas).

The (limited, in this case) data from the flight is only stored as long as the altimeter is on. So don't pull the battery yet!

Using an FTDI chip, connect GND on the FTDI to the debug pin nearest the LED (green lead in the photo below) and the RX pin on the FTDI to the debug pin nearest the logo (blue lead in the photo below). Open a serial terminal (screen /dev/ttyUSB0 on Linux - you can probably use Arduino if you're running an inferior OS). You should see a bunch of text output. It's just a repeating message, so you only need one copy of it.

[[File:Example.jpg]]

== Random things ==

== Accessing Source Files ==

Source files for the altimeter are in SSI's Subversion repository (where all Altium files are hosted). If you are an SSI member, talk with Logan Herrera or Thomas Teisberg about getting access.

The intent is to make all of the hardware open source. This will likely be done after the project has reached a stable point.

SSI Altimeter

2016-02-20T07:49:42Z

Thomas:

The SSI Altimeter (also known as the "Dual Deploy Altimeter" or "Althometer") is an ongoing project to develop a low-cost, customization, and easily programmable altimeter for SSI-run rocketry certifications.

[[Category:Rockets]]

{{rocket-project
| header = SSI Altimeter
| img link =
| launch details =

== Project Status ==

The altimeter is currently under development. An revision 1 has been produced and is currently undergoing testing.

== Using the Altimeter ==

=== First Steps ===

Mount the Altimeter and a single-cell LiPo battery however you like in the rocket. Note that there must be a vent hole to the altimeter or else it cannot detect changes in pressure. (At this point, it is not orientation dependent, however this will eventually change.)

Before connecting the battery to the altimeter, go ahead and connect the deployment charges to the green terminal blocks. They are labelled on the bottom of the board. For the vast majority of applications, the polarity does not matter.

=== Power On ===

''The altimeter is very sensitive to wind. It works fine when inside of a rocket body, but it gets very confused when its sensor is directly exposed to the wind.'' For this reason, there is a delay before the altimeter starts doing anything. It's important that you get the altimeter installed in the body tube (or nose cose) before this delay expires.

When the altimeter powers up, you will see:
1. White LED blink
2. Program code blink (in this case: green / red)
3. White LED blink
4. Green LED - This green LED stays on during the startup delay.

By the time the green LED goes off, the altimeter should be in the body tube or otherwise shielded from the wind. The altimeter will also take this as its zero altitude reading, so you should be fairly close to the launch site elevation by now.

Miss it? No problem. Press the little button in the top left to reset to the beginning. As long as no charges fired, there's no problem with just resetting.

=== In Flight ===

For this launch, the altimeter is programmed to:
1. Wait until the rocket reaches at least 900 meters.
2. Keep waiting until the rocket has fallen at least 100 meters.
3. Deploy charge 1 after the rocket passes 700 meters.
4. Deploy charge 2 after the rocket passes 600 meters.

=== Recovery and Post-Flight ===

When you get the altimeter back, it should have a solid blue LED. If it doesn't, disconnect the (potentially undeployed) charges and note the color of the LED (and tell Thomas).

The (limited, in this case) data from the flight is only stored as long as the altimeter is on. So don't pull the battery yet!

Using an FTDI chip, connect GND on the FTDI to the debug pin nearest the LED (green lead in the photo below) and the RX pin on the FTDI to the debug pin nearest the logo (blue lead in the photo below). Open a serial terminal (screen /dev/ttyUSB0 on Linux - you can probably use Arduino if you're running an inferior OS). You should see a bunch of text output. It's just a repeating message, so you only need one copy of it.

PHOTO

== Random things ==

== Accessing Source Files ==

Source files for the altimeter are in SSI's Subversion repository (where all Altium files are hosted). If you are an SSI member, talk with Logan Herrera or Thomas Teisberg about getting access.

The intent is to make all of the hardware open source. This will likely be done after the project has reached a stable point.

SSI Altimeter

2016-02-11T05:20:03Z

Thomas:

SSI Altimeter

2016-02-11T05:18:24Z

Thomas: Created page with "The SSI Altimeter (also known as the "Dual Deploy Altimeter" or "Althometer") is an ongoing project to develop a low-cost, customization, and easily programmable altimeter for..."

The SSI Altimeter (also known as the "Dual Deploy Altimeter" or "Althometer") is an ongoing project to develop a low-cost, customization, and easily programmable altimeter for SSI-run rocketry certifications.

== Project Status ==

The altimeter is currently under development. An revision 1 has been produced and is currently undergoing testing.

== Accessing Source Files ==

Source files for the altimeter are in SSI's Subversion repository (where all Altium files are hosted). If you are an SSI member, talk with Logan Herrera or Thomas Teisberg about getting access.

The intent is to make all of the hardware open source. This will likely be done after the project has reached a stable point.

Pulse Position Modulation

2015-11-06T07:35:53Z

Thomas:

''This article is currently just a list of resources for now. It will be (eventually) expanded to explain more concepts.''

== Understanding PPM ==

This is a good resource for understanding how PPM works:

http://www.pcbheaven.com/wikipages/Pulse_Position_Modulation/

The part we're most interested in is actually Differential Pulse Position Modulation (DPPM) because it is both more efficient and easier to implement.

== Digging a little deeper ==

Stanford happens to have one of the world's experts on optical encoding on the faculty. One of Professor Kahn's more accessible papers is available here:

http://ee.stanford.edu/~jmk/pubs/dppm.pdf

This is a good introduction to why DPPM is one of the most efficient optical encoding techniques.

== What to play with ==

For those of you working on transmitting data across your 3 CM board, I'd suggest the following development process:

1. Get 4-DPPM working. In other words, output a constant length pulse followed by four possible delay times representing binary values 00, 01, 10, and 11. Write corresponding code to decode this and output the result over serial.
2. Experiment with what the minimum pulse timings you can use are. There will be some point at which you reach the limit of how fast you can detect the pulses.
3. Try to generalize your code to work for 4-DPPM, 8-DPPM, 16-DPPM, etc.
4. Add some form of automatic error detection ([checksums http://computer.howstuffworks.com/encryption7.htm]) and try to get your receive microcontroller to quantify the percent of successful transmissions.

== Random notes on the board ==

* The transimpedance amplifier doesn't get the signal up to logic level, so we're using an analog input to read the signal. That's not as fast as amplifying the signal in hardware (which is what the new amplifier board does) and then reading it with a digital input. This will likely be your limiting factor.
* There's a potentiometer near the big chip next to the LED. Turning that to the right increases the brightness of the LED. If you turn it too far to the right, the LED will give you a bright flash and permanently die. Keep it to a half turn or less.

== PPM Code Repositories ==

https://developer.mbed.org/users/tteisberg/code/Optical3cmRX/
https://developer.mbed.org/users/tteisberg/code/Optical3cmTXnucleo/

Ask Thomas for access.

[[Category:Optical Communications]]

Pulse Position Modulation

2015-11-06T07:31:23Z

Thomas: Created page with "''This article is currently just a list of resources for now. It will be (eventually) expanded to explain more concepts.'' == Understanding PPM == This is a good resource fo..."