topic Re: LCP54628 MCAN Configuration in LPC Microcontrollers

LCP54628 MCAN Configuration

FFOXZ — Wed, 31 May 2023 18:59:07 GMT

Hello!

Please, someone could help me with CAN protocol configuration?

In this project I am using OM13098 development board with LPC54628 microcontroller and I'm working with MCUXpressoIDE v11.6.0 and with version 2.12 from SDK.

I saw and compiled the examples from SDK, but I think there is something weird with that examples.

I'm trying to do a loopback teste with the CAN Protocol, but following example code (lpcxpresso54628_mcan_loopback) is possible do this loopback without phisical connection beteween CAN0_RD (RX) and CAN0_TD (TX). In this way, isn't useful for one real application. It's right?

I expect to develop a example code with CAN0 working by interruptions and just works when I'll physically connect RX with TX like in serial communication.
In future, I intend to develop a master CAN with CAN1 and a slave CAN with CAN0.

Below there is the example code who I'm using and trying to unveil this mystery. If someone could help me, please could you contact me?

Re: LCP54628 MCAN Configuration

frank_m — Thu, 01 Jun 2023 07:11:27 GMT

There is a "mcan_interrupt_transfer" example in driver_examples in the SDK.
I am referring to the LPCXpresso54628 SDK here which I use occasionally.
Though I must admit I never tried any CAN example with this board.

To use CAN (not the internal loopback mode), you should have proper transceivers attached, albeit for just two nodes, a direct (TTL level) connection might work.

Or, you can try to modify your loopback example, and initialize the CAN peripheral in full CAN mode.
Perhaps taking the code from the interrupt_transfer example as template.

By the way, I had included a CANopen middleware package in my SDK, which provides 4 CANopen examples. Not sure if that would be helpful for you.
My company's products use mainly CANopen for their ECUs.

Re: LCP54628 MCAN Configuration

FFOXZ — Thu, 01 Jun 2023 12:08:45 GMT

Hello @frank_m !!!
First I should say thank you for yout reply my question!
I saw the example mcan_interrupt_transfer in the same SDK like you said, but I think this is useful for 2 boards and works with callbacks functions.

In my case don't have 2 boards here and I need to develop a code with interrupt functions, this is a reason I'm trying to use mcan_loopback example for my model.
And about the transceivers, I trying to do something before read the "real" CAN Protocol. I'm just trying to send some knowed package and receive the same package, exactly like in serial communication. But the example loopback is weird, like I said before.

I'll follow your first ideia about initialize the CAN peripheral in full CAN mode.
Could you explain better your ideia? And could you show me who function are you thinking to change?

About your CANopen middleware package, if it's possible you share with me, I really be grateful for you send me. Because maybe it could be useful for my project.

Best regards.

Re: LCP54628 MCAN Configuration

frank_m — Thu, 01 Jun 2023 13:57:35 GMT

If I remember correctly, the loopback mode is internal, i.e. the connection between Tx and Rx is on silicon.
Thus the signal never "leaves" the MCU.
It is a setting in the MCAN config register, you might need to consult the MCU user manual / datasheet.

An option interesting for you would be to turn off this loopback mode, and instead connect CAN Tx and Rx externally, i.e. on the board. This should yield the same result.

The interrupt-based example would be one example of how to configure the MCAN peripheral for normal operation.

> And about the transceivers, I trying to do something before read the "real" CAN Protocol.

Transceivers do only affect signal levels. As you might know, CAN uses a differential signal with different voltage levels.
But you can connect two CAN devices directly (without tranceivers), provided they have the same digital levels (supply voltage). Ground loops might become problematic, though.

Re: LCP54628 MCAN Configuration

FFOXZ — Thu, 01 Jun 2023 15:43:08 GMT

Exactly, this example use the silicon internal loopback.

>An option interesting for you would be to turn off this loopback mode, and instead connect CAN Tx and Rx externally, i.e. on the board. This should yield the same result.

This is exactly what I want to do.
But when I do this, I don't receive the same buffer as I send.
I changed somethings in code and remove this internal loopback. So now, this code work if external loopback, but my received frame data isn't the same as I send. Below there is a photo from my terminal. Maybe it can be better explained.

Re: LCP54628 MCAN Configuration

Alice_Yang — Fri, 02 Jun 2023 03:25:11 GMT

Hello @FFOXZ

About external loopback mode, please refer to UM10912 -> 5.14.1.7.1 External loop back mode, after configure based on loopback demo,

if still can't work, you can use peripheral tool to configure as below:

Alice

Re: LCP54628 MCAN Configuration

frank_m — Fri, 02 Jun 2023 05:07:15 GMT

I would definitely consult the manual, as Alice_Yang suggested.

To be honest, I don't have much experience with the LPC MCAN peripheral, though I dealt a lot CAN on other architectures.

I am not sure if the internal loopback mode requires the GPIO pins (for Tx/Rx) to be configured as alternative (CAN) functionality. You could compare this with the interrupt example.
The pin initialisation code of the project is usually found in pinmux.c / pinmux.h.

Re: LCP54628 MCAN Configuration

FFOXZ — Mon, 05 Jun 2023 12:41:28 GMT

Hello Frank!
Thank you for your advice again.
I'm reading better all 35.14 chapters like Alice recommended.

About the pins, I confirmed it is being initialized with alternative (CAN) function in all example.
I think the point here is "remove" this internal connection between
tx and rx like explained in Figure 139 (section 35.14.1.7.2).
I'll publish this Figure 139 here.

Re: LCP54628 MCAN Configuration

FFOXZ — Mon, 05 Jun 2023 12:55:23 GMT

Hello @Alice_Yang !!!

I really need to say thank you for your advice. I read the documentation and now I could understand how this examples works.
But my idea is using the CAN RX with the CAN TX outside of microcontroller, work like a real external loop back and don't have a "jumper" inside of microcontroller like this tests modes.
Please, could you know a way to do this? Do you know a way to disable this "jumper" and I could read the real data what I transfer?
For example: I send eight equals data (0x55) and read the same data on CAN RX.
Below is the same photo as I send to @frank_m to be more explained what I want to do.

Re: LCP54628 MCAN Configuration

frank_m — Mon, 05 Jun 2023 13:48:22 GMT

I think the picture labelled "external loop back mode" is incorrect. The drawing contradicts the very term.

Perhaps a Copy&Paste error which requires quite a bit of work on the proofreader's side.

Re: LCP54628 MCAN Configuration

FFOXZ — Mon, 05 Jun 2023 13:58:36 GMT

I don't think so, because in this case the output is readable with oscilloscope in CAN0_TX and just when I connect the tx with rx.
But in serial terminal isn't read the same package.

Re: LCP54628 MCAN Configuration

Alice_Yang — Wed, 07 Jun 2023 08:27:35 GMT

Hello @FFOXZ

The term "loopback" here is a special term for CAN specification, which mean's do not need external connection.

If you want a actual external CAN test, which MUST need CAN transceiver and another CAN node for test. you can use some "USB-CAN" adapter to try this.It is not possible to connect directly CAN_TX and CAN RX for on-board CAN test.

Alice

Re: LCP54628 MCAN Configuration

FFOXZ — Wed, 07 Jun 2023 09:36:14 GMT

Hello @Alice_Yang !!!

Thank you again for answer me.

Really?? Yesterday I was trying to use the example mcan_interrupt_transfer to try again another test join CAN_RX and CAN_TX directly, like I said before. My oscilloscope show me all transmitted package but in debug mode appear this error 0x1849 --> kStatus_MCAN_UnHandled.

Excuse me but I'll insist a little bit... But it CAN protocol is similar to Serial communication, isn't?

More one doubt... So, in same board, I could do this external test with both CAN's? For example, I can connect the CAN_0 with the CAN_1, using transceivers.

Could I use this mcan_interrupt_transfer example for this test?

Tks,

Cvsta.

Re: LCP54628 MCAN Configuration

frank_m — Wed, 07 Jun 2023 10:12:11 GMT

> Excuse me but I'll insist a little bit... But it CAN protocol is similar to Serial communication, isn't?

You are right, at this level, CAN is just a digital signal like RS232 or SPI.
You can connect two nodes directly, provided they have the same digital levels and specifications (and the cable is not too long).

By the way, I think there are several relatively cheap CAN breakout boards available, like in the Arduino/maker scene. Those would be a great start to get a prototype working, because very few evaluation boards come with CAN hardware.

Re: LCP54628 MCAN Configuration

Alice_Yang — Thu, 08 Jun 2023 02:18:14 GMT

Hello @FFOXZ

1） "More one doubt... So, in same board, I could do this external test with both CAN's? For example, I can connect the CAN_0 with the CAN_1, using transceivers."

->> Yes.

2）There is a description about CAN transceiver:

Alice

Re: LCP54628 MCAN Configuration

FFOXZ — Thu, 08 Jun 2023 03:16:48 GMT

Hello @Alice_Yang !!!

Thank you again for more this documentation.

Now I'll try develop a new test using CAN_0 with CAN_1 and publish my code here as soon as possible.

More one question, I saw there is a software Can Open File Player. It is necessary to read CAN package? Or there is another software necesary to read CAN package?

Best Regards.

Cvsta.

Re: LCP54628 MCAN Configuration

Alice_Yang — Thu, 08 Jun 2023 06:40:54 GMT

Hello @FFOXZ

1) "More one question, I saw there is a software Can Open File Player. It is necessary to read CAN package? Or there is another software necesary to read CAN package?"

->> Do you mean a PC software? connect with "USB-CAN" adapter?

For start, if you only have one board, as Frank said, you can consider "relatively cheap CAN breakout boards available, like in the Arduino/maker scene. Those would be a great start to get a prototype working, because very few evaluation boards come with CAN hardware.".

Or use "USB-CAN" adapter.

2)If you use "mcan_interrupt_transfer" demo, there is hardware requirements and boards setting in readme.txt:

Alice

Re: LCP54628 MCAN Configuration

frank_m — Thu, 08 Jun 2023 07:24:51 GMT

> More one question, I saw there is a software Can Open File Player. It is necessary to read CAN package? Or there is another software necesary to read CAN package?

CANopen is a standard based on CAN, restricting epsecially the ID usage. https://en.wikipedia.org/wiki/CANopen
Unless you don't have a CANopen environment (and don't plan on using one), I would not start with those examples. They add another layer of complexity.
I used to work a lot with such CANopen devices in my company.

In regards to mentioned CAN breakout boards, me and Alice_Yang were speaking about different things.
Those breakout boards mentioned by me are for the MCU side, and would extend any eval board.
An USB CAN adapter is useful/required for the host/PC side.
My company uses a few Vector pods, but mostly the cheaper PCAN devices : https://www.peak-system.com/PCAN-USB.199.0.html?&L=1

Re: LCP54628 MCAN Configuration

FFOXZ — Fri, 09 Jun 2023 13:33:54 GMT

Hi @Alice_Yang

This description about CAN Transceiver as you send is from a public document?

Would it be possible for you to share this document?

Tks,

CVSta

Re: LCP54628 MCAN Configuration

FFOXZ — Fri, 09 Jun 2023 13:42:11 GMT

Hello @frank_m

Thank you to send me all this links and information about USB CAN.

But thinking better I won't need to use these softwares or CAN breakout boards.

Because, my ideia is connect one board CAN Master with another board CAN Slave. So I think just testing the connection and sending a package and receiving the same package will be successfully.

Tks.

CVSta