Here we go again...
if(OS != Linux)
  CAN = Easy;

In one respect, I agree with Sarah's statement in that the only active node in an FC failure is the recovery node. Nothing else really matters.

That said, if you *must* have some sort of non-usb back channel communication, CAN is the way to do it. It's easier than any other protocol for the same level of performance and robustness (bar NONE). I understand that there is a lot of ill feelings on this list toward CAN, but that was an issue with CAN implemented with specific hardware and a specific OS and driver, all done without any solid tools (which are not needed at all once communication is established).

There is a reason CAN is used for safety critical equipment. The reason is that it is reliable and easy to implement. If someone here is nervous about how difficult it will be to implement, then let Dave and I have a chance to prove otherwise.

Quoting Sarah A Sharp <>:

My question (before we jump into CAN or anything else) is, "What nodes
need to talk to each other if the flight computer goes down?"

If the flight computer is down, the goal should be to get the rocket
to the ground safely.  I don't think there's much point in trying to
use CAN to log data.  Given the goal of a safe landing, what nodes
*really* need to talk to each other?

If it turns out that only two nodes need to talk to each other, why
bother with CAN?  Why not just run one serial connection between the
two?  I'm concerned that we're adding too much complexity for what
should be a really simple backup system.


On Sun, Feb 1, 2009 at 12:07 PM, Dave Camarillo
<> wrote:
Hi All, it looks like Denx does have drivers for the CAN hardware on
the 5200. It appears to be a derivative work of Peak Systems
( PCAN software. I skimmed the source code
and they have a driver that hooks the PCAN driver (they also support
devices such as the SJA1000 chip and a couple other products from
peak-system). The include in the source tree a command line app for
transmitting and receiving messages as well.

Based on skimming the source code and looking at the pcan web site it
appears to support 2.4 and 2.6 kernels, and the peak site indicates
that they support the PF_CAN (SocketCAN) stuff built into newer

I'm wondering, maybe Josh/Jamey could bring the flight computer on
tuesday and maybe we can play with this a little?



On Sun, Feb 1, 2009 at 5:58 AM, Andrew Greenberg <> wrote:
We've looked a bit at our schedule for the capstone, and the decision
between CAN and a UART backchannel really, really, really have to be
made in the next three weeks.

To even consider CAN as a backchannel, we have to have the MPC5200 talk
CAN on its native CAN peripheral. That means digging up Denx's MPC52000
CAN peripheral drivers and actually seeing them work, and testing them a

We'll talk about this more on Tuesday, but I just wanted to warn
software folks - I guess mostly Dan and Dave here - that we need to know
stuff, soon. We'll have the MPC5200 FC at the next meeting for you to
play with, and I'll bring my CAN2USB adapter.


Andrew Greenberg

Portland State Aerospace Society (  P: 503.788.1343  C: 503.708.7711

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