The 2009 Control System Q&A Thread

[rfolea]

Originally Posted by crake

As the 2009 control system is finalized, the official FAQ posted at http://first.wpi.edu/2009_FRC_Controller_FAQ_FINAL.pdf will be ...

Can we request that a rev # and date be added to this FAQ so we know when it has been updated?

[Greg McKaskle]

Cameras:

Because the cRIO has 100Mb enet, no firewire or USB. This leaves us in the domain of security cameras and IP cameras. They range from quite cheap to quite expensive. Most can do 640x 480 color, but cannot quite do 30fps at that size. Dropping image size to 320x240, we can easily acquire 30fps. This doesn't mean that 30fps can necessarily be processed for content, though.

Other limits are likely to be imposed, such as a 1 or 2Mb limit of upload images per team.

Greg McKaskle

[Leav]

Originally Posted by Greg McKaskle

Cameras:
Other limits are likely to be imposed, such as a 1 or 2Mb limit of upload images per team.

Are you talking about uploading to the driver station?

The idea is new to me, and sounds exciting... but why would you limit the size of the image?
If bandwidth is the problem wouldn't it make more sense to just throttle the bandwidth?

with such an amazing array of possibilities I would hate to see rules crippling the control system. give us the control system and let us push it to the max!
(obviously stuff like bandwidth would need to be kept in check so that everyone has a fair chance on the field and no one team is eating up the bandwidth for everyone else...)

-Leav

-----------------------------------------
Edit:
since the timeframe is set (let's say 2:15 minutes) It could be argued that a size limit IS a bandwidth limit... but obviously it isn't because if that size can max out the bandwidth for more than a few seconds than the size limitation is useless.

In other words if it takes 3 minutes (or even 1 minute) to transfer a 2mb file then setting the limit to 2mb as a way of controlling bandwidth is futile.
if it takes 3 seconds to transfer that file than obviously the system can handle a large enough bandwidth to support unlimited file size, providing that the the bandwidth be throttled down to a setting where it takes say 6 seconds to transfer a 2mb file.

[Greg McKaskle]

Sorry, I meant 1 or 2 Mb mega-bits per second. In other words, a QOS limited by the network. In Atlanta, we were uploading moderately compressed jpgs at 15fps at 320x240.

All of this is of course dependent upon the actual throughput of a wifi network tuned for the field. 54 Mb is the theoretical limit, but it is likely to wind up being more like 1/4 of that depending on protocol, encryption, interference, etc.

Greg McKaskle

[Jon236]

Greg,

This question reflects a response to Danny Diaz on another thread.

Can the final software version allow the capacity to model the mechanical system? That is, will there be VI's that represent virtual motor controllers, gear ratios and motors so that power consumption, as well as programming, can be tested before we (the programming team) yield the system to the build team?

[tdlrali]

This is more about Labview than the control system:

Will teams have access to Labview addons such as the Control Design Module or the PID toolkit? If so, will these be available through the C libraries as well?

[Greg McKaskle]

Will teams have access to Labview addons such as the Control Design Module or the PID toolkit?

That is the current plan. I'm not certain if it will be the complete package, or a subset. Honestly, I'm not very familiar with the toolkits.

Greg McKaskle

[dcbrown]

Q. The WPILIB functionality will include both LV and C libraries, but will exisiting NI LV libraries be converted into C libraries for team use also (such as aforementioned PID) or remain available in LV only? If C library form will eventually be available, is NI, FIRST, or WPI responsible for the conversion?

Q. When will the VxWorks C/C++ API as it currently exists (without FIRST/WPILIB add ons) on cRIO be released to FIRST teams from NI? For example, RPTs are not supported and there is a special driver/interface to the FPGA as an add on to VxWorks for the cRIO.

[dcbrown]

Q. In the past you could convert some Analog inputs to digital I/O increasing the available input/outputs available by up to an addional 16 lines - will the same functionality exist in cRIO are are we limited to just 14 DIO on the sidecar?

[crake]

Originally Posted by dcbrown

Q. In the past you could convert some Analog inputs to digital I/O increasing the available input/outputs available by up to an addional 16 lines - will the same functionality exist in cRIO are are we limited to just 14 DIO on the sidecar?

A: The Analog Input and Digital I/O lines are fixed and defined by the module. However you have two 9201 AI modules and two 9403 DIO modules in the system with bumpers and sidecars, so you have:

16 channels, 12-bit, +/-10V, Analog Input
each bank of 8 channels has a scanned sampling rate of 500kHz

20 PWM outputs with 6V selectable power (jumpers) for servos
28 GPIO, TTL
16 forward/reverse relay outputs
2 SPI interfaces

In addition you have 8 channels of 12V DO for solenoid and pnuematics.

[Greg McKaskle]

Originally Posted by dcbrown

Q. The WPILIB functionality will include both LV and C libraries, but will exisiting NI LV libraries be converted into C libraries for team use also (such as aforementioned PID) or remain available in LV only? If C library form will eventually be available, is NI, FIRST, or WPI responsible for the conversion?

I'm not sure about across the board. From the beginning, we intended to have WPILIB and vision in both languages. For other libraries that are made available in LV, NI may be able to provide C versions if they exist, or wrappers to any underlying C code. But the word converted implies an automatic process, and in case it isn't clear, LV doesn't convert to C, so that isn't an option. Since the goal is really to have a nice parity and symmetry between C and LV, I think between NI, WPI, and the rest of the community, we will have a really nice set of libraries for both languages.

Originally Posted by dcbrown

Q. When will the VxWorks C/C++ API as it currently exists (without FIRST/WPILIB add ons) on cRIO be released to FIRST teams from NI? For example, RPTs are not supported and there is a special driver/interface to the FPGA as an add on to VxWorks for the cRIO.

The toolchain can already be downloaded from WindRiver, as can a demo of LV from NI. C tools targetted for cRIO aren't currently a standard product, so I'm afraid that the first availability will be nearer to when the HW is available.

Greg McKaskle

[Qbranch]

First, some quick background. I love NI hardware, but really don't like LabView. At my Co-Op we used a whole bunch of your hardware (M-Card, 8-port serial card, 4 axis motion control card, can bus module, VBAI) to build a testing robot and ran it from Visual Basic in Windows XP.

I really like the ease of using calls to the CVI libraries... will the same CVI calls be available in the Wind River C environment?

Also, I don't know how much of your (awesome) vision system you're including, but do you know if we'll be getting vision assistant or VBAI?

If you can pick... I find VBAI much easier to use and more powerful, and it's very easy to load up an inspection with a CVI call.

How much resolution do the PWM outputs have? What frequency do they output at?

One last question on the 150lb weight limit: If this is true, why are batteries and bumpers not included in the weight limit? FIRST robots currently weigh a good deal more than 150lb with a full complement of bumpers and batteries. Sorry, I was thinking 120lb not, 150.

Thanks,

-q

[crake]

I'll focus on the HW answers (Greg can snag the SW):

Originally Posted by Qbranch

How much resolution do the PWM outputs have? What frequency do they output at?

A: The PWM periods are configurable and the 9403 DIO module has an update rate of 6.625us. The period would depend on the type of motor controller that is used. While I can not speculate on future motor controllers, I can say that the IO module was selected with this update rate (and the resulting resolution/period ratio) in mind.

One last question on the 150lb weight limit: If this is true, why are batteries and bumpers not included in the weight limit? FIRST robots currently weigh a good deal more than 150lb with a full complement of bumpers and batteries.

I don't know that answer for 2009 - that will be completely up to FIRST.

[Russ Beavis]

Regarding the 150lb weight limit, I certainly hope that a 120 lb robot + 15 lb bumpers + 13ish lb battery doesn't "weigh a good deal more than 150 pounds".

A few years back, we learned that not all SLA batteries are created equal. There are mass differences between samples and we found out that robot weight changed substantially depending on which battery was installed during inspection. So... for consistency, we now weigh robots without the 12V SLA battery installed.

Russ Beavis
Chief Inspector

[Greg McKaskle]

Originally Posted by Qbranch

I really like the ease of using calls to the CVI libraries... will the same CVI calls be available in the Wind River C environment?

Also, I don't know how much of your (awesome) vision system you're including, but do you know if we'll be getting vision assistant or VBAI?

CVI is not released for cRIO, or for other RT targets. The WPILib libraries will be included with the ANSI, and posix libraries provided by WindRiver.

I'm not positive about the licensing of the visions stuff. I think that Vision Assistant will be in the kit.

Greg McKaskle