SAM7S256 - CAN J1939

nkarioto · **Joined:** Mon May 10, 2010 4:47 pm **Posts:** 3

Hello everybody,

I am using an AT91SAM7S256 to gather and process data from various instruments installed on an experimental boat hull:

1) UART IMU
2) UART GPS
3) USB interface with PC

Now, after working for about 3 weeks with all these devices, I got them to work and correctly gather the data as required.

However, my supervisor asked me to include a water speed sensor to the setup. I have one already but it is using a CAN J1939 Protocol. I have no idea how to integrate that to the Evaluation board as the only ports left are SPIs. I found some CAN to SPI converters... Is that the only solution or is there ANY other way to use the AT91SAM7S256 chip to interface with a CAN protocol?

I am struggling with this for quite a while... so any suggestion or help is very very welcome.

I hope to hear from somebody soon!
Nick

jrsimma · **Joined:** Fri Apr 08, 2011 4:13 am **Posts:** 2

If you need J1939 software for your sensors, we support a J1939 protocol stack for Atmel CPUs. To learn more about our J1939 or about our protocol stack for Atmel, see http://www.simmasoftware.com/j1939.html

Thanks,

JR

jrsimma · **Joined:** Fri Apr 08, 2011 4:13 am **Posts:** 2

Sorry, I should have also included a link to a J1939 Introduction. Here it is http://www.j1939-introduction.com

Thanks,

JR

Bob_Keil · **Joined:** Mon Mar 28, 2011 7:10 pm **Posts:** 6

Hello

You will need to connect a CAN controller and a transceiver to your AT91SAM7S256.

You could look at the Microchip MCP2515 but I heard one time it had plenty of bugs - so check the errata sheet first. It connects to a processor via SPI.

Otherwise, switch to a different SAM7 chip that has an integrated CAN controller (transceiver is nearly always external) or add an external CAN controller to AT91SAM7S256 via external address/data bus.

CAN controllers are rather complicated so too tough to bit bang. Just not worth the trouble.

J1939 is reasonably easy to extract a message or two. Might have to request data or it will just come spewing out of your device.

Do you have examples of what this device is putting out ?
Will be 29 bit id and look something like 18EEFF03 53 41 80 06 00 03 02 00
J1939 works at 250 Kbps (half speed of automobiles)

Do you have a CAN bus sniffer ? Are cheap and worth getting - will save lots of time.

Bob
ARM

SAM7S256 - CAN J1939

Who is online