topic Re: MQX CAN bus API usage in MQX Software Solutions

MQX CAN bus API usage

kaif — Fri, 04 Apr 2014 10:29:59 GMT

Hi,

I am writing my first small application using MQX 4.0 and it's CAN bus drivers on a K60 tower board. I've had a look at the kflexcan example code that comes with the MQX bundle. After playing around with it, I'm now wondering if I understand the concept behind it correctly. What I mean is this:

The kflexcan API offers a FLEXCAN_Rx_message() that takes a mailbox as parameter. Now, a mailbox is initialized by FLEXCAN_Initialize_mailbox() that takes a specific CAN ID as parameter. Later you just call _lwevent_wait_ticks() which will block the current task until a message with the requested CAN ID pops up in the mailbox. So far, this is very comfortable and easy to use.

But let's say I'm working with a large number of different CAN IDs. How does this approach work then? Do I have to add a mailbox for every CAN ID that can appear on the bus? That doesnt sound like the way to go..

What I would expect is a function that takes a CAN ID as parameter and then blocks the current task until it receives such a message or hits a timeout. Something like this: can_message_t can_read(can_id_t id, uint_32 timeout). For my purposes this wouldn't need to be thread safe. Do I have to implement such a function myself? How are you guys working with the provided API, regarding multiple CAN IDs?

Thanks for any input!

Regards,

Kai

Re: MQX CAN bus API usage

Kan_Li — Wed, 09 Apr 2014 08:31:08 GMT

Hi Kai,

For your case, I think you may use the RX FIFO feature, which is supported in MQX 4.1. You may download it and find it in K70's BSP.

Hope that helps,

Have a great day,
Kan

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Re: MQX CAN bus API usage

kaif — Wed, 09 Apr 2014 09:30:25 GMT

Unfortunately this is not an option for me as I'm using MQX 4.0.2 and currently cannot switch to 4.1 because of some troubles I'm having with the Atheros WiFi driver.. :smileysad:

Re: MQX CAN bus API usage

Kan_Li — Thu, 10 Apr 2014 08:15:56 GMT

Hi Kai,

Maybe you can port the flexcan driver from MQX 4.1 to 4.0.2. You may find there is option for TWR-K60N512 as below:

Or PE drivers can also be a good option, you may disable flexcan in user_config.h and use the driver code generated by PE instead.

Hope that helps,

Have a great day,
Kan