CAN communication between TM4C123G AND TM4C129 microcontrollers.

Hello Ninand

Did you check the TivaWare examples before posting the forum post?

Regards
Amit

Yes Amit, I did give it a check now.
The peripherals folder within TivaWare examples has the simple CAN message sample code.
But in order to implement the sample code on two Tm4C123G microcontrollers, which CAN transceivers are the most compatible?
Also can you help me with connections to be made in order to create a differential CAN bus with CAN high and CAN low?

Thanks in advance.

Hello Ninad

I have used SN65HVD1050 CAN Transceiver in the past. You can refer to the DK-TM4C123G Schematics for CAN Transceiver,

Regards
Amit

Hello Ninand,

I did some work on this

https://e2e.ti.com/support/microcontrollers/tiva_arm/f/908/p/433816/1608971#1608971

Please go through the link. I have used MC2551 as a CAN transreceiver. You need to connect 120 Ohm resisters across CAN H and CAN L. And I have used example given in TIVAWARE. They are quite useful.

Go through the transreceiver datasheet and TIVAWARE example , I guess they are sufficient.

 

Regards,

Anup

Thank you Anup for your prompt reply.
Is it possible to use only one TIVA Launchpad both as a transmitter and a receiver?

Hey Amit, i got samples of SN65HVD251P CAN tranceiver.
Shall i go ahead with the same or shall i get samples of SN65HVD1050 and use them instead?
Or MCP2551?

Thanks in advance.

Hello Ninand,

SN65HVD251 should be OK. Note that SN65HVD1050 is a High Reliability part. Also do make sure that the specifications meet your requirements irrespective of which part you select.

Regards
Amit

Thank you Amit.
I'll try to implement the circuit and get back to you if anything goes wrong.

Hello Amit, while trying to compile the program for simple CAN tx as provided in the TivaWare folder, i am encountering these errors on CCsv6

Doc1.docx

Hello Ninad

Did you extern the CANIntHandler in the startup file. Also it looks as if there is a typo as well. A void function is always "void XYZ" and not "voidXYZ".

Regards
Amit

I already rectified the typo Amit....

Also in the startup.ccs.c file I have replaced the InterruptDefaultHandler for Can0 by CanIntHandler......Still there are errors  such as statement unreachable.....what further changes should I make?  Thanks in advance.

Hello Ninad,

Can you please share the compilation log which shows the error and the file in which the errors are present!

Regards
Amit

Description Resource Path Location Type
#112-D statement is unreachable simple_tx.c /CAN line 425 C/C++ Problem

Hello Ninand

How am I supposed to know what is at line 425? Also this would not be an error but a warning.

Regards
Amit

Hello Ninad

As I suspected correctly, it is a warning because the "return(0)" is preceeded by a while(1) condition. Since the CPU loop will not exit the while(1) it will never reach return(0) and hence the warning.

Regards
Amit

so shall i comment the return statement?

And is the extern statement entered by me in the startup file in correct format?

Hello Ninad

Yes, the extern is correct and commenting out the return line will only remove the warning.

Regards
Amit

Hello Amit,

I just received a new TIVA C123 GXL launchpad. I have loaded the simple can_tx program on it and performed the necessary changes such as extern and interrupt handler things.

The build is sucessful. 

But when i am debugging the code, there is no output on my PUTTY terminal...it is just blank.

And yeas, i recently updated my PC to windows 10, so has that go to do something with this?

Hello Ninad,

Does the device manager enumerate the COM port?

Regards
Amit

Hi,

Please note you need two boards with CAN interface chip, to implement a CAN bus (a transmission line, closed at both ends by its characteristic impedance, with stubs at both ends) to be able to do CAN communications. Otherwise you will be for ever in error (CAN 2.0B standard, Bosch).

Hey Amit,
I am using the simple_tx program for CAN transmission on my tiva TM4C123GH6PM board and simple_rx for reception on my tiva TM4C1294NCPDT board.
Both builds are sucessful.
i have used SNHVD251P IC as my transceiver.
Now, when i am debugging the codes, on my transmitter side the puTTy terminal gives me a message "cable connected"?
and its is blank on the receiver side.

Please help.

Thanks in advance.

I am using the simple_tx program for CAN transmission on my tiva TM4C123GH6PM board and simple_rx for reception on my tiva TM4C1294NCPDT board.
Both builds are sucessful.
i have used SNHVD251P IC as my transceiver.
Now, when i am debugging the codes, on my transmitter side the puTTy terminal gives me a message "cable connected"?
and its is blank on the receiver side.

Please help.

Thanks in advance.

Hi,

Is your transmission line closed at both ends with its characteristic impedance? (i.e. 2x 120 ohm parallel resistors if you used a 50 mils(1.27mm) pitch flat cable).

Please also read this document: (not the best one, TI had a better ones several years ago....) 

hey Petrei,

Please review these images.

This is my setup.

I am using 2*100 Ohms in parallel.

still there is no communication happening.

On TM123GH6Pm side the following connections are made:
PB4-CAN0RX-PIN4 of SNHVD251P
PB5-CAN0TX-PIN1 of SNHVD251P.

Please let me know whether PIN8 of the transceiver IC should be connected somewhere or left open?

Hi,

Pin 8 should be connected to ground; left open may shut off the device, leaving alive only the receiver.  Use gound connection until  you establish communication.

About your picture: you need 60 ohm resistors on each side of the line; use flat cable of 6ft/1.8m to start with, not an inch.

Use also an oscilloscope to see/ check the waveform.

Hello Petrei,

Should we be asking for the schematic rather than wire connections to review the setup as well?

Regards
Amit

Hello Ninad

Your last forum post was blank!!!

Regards
Amit

I replied with schematic Amit!!

Hello Ninad

And for some reason I cannot see it in the post

Regards
Amit

I posted an image...shall I do it again?

Also...I have sent you a personal message regarding the same.

Hello Ninad

Yes, I did see your message and I have the following questions for which I would like to see the schematic of the connections

What about GND on the CAN bus? Also how is the termination resistance connected and its value.

Regards
Amit

Termination resistance is 120 ohms on the tx side and 120 ohms on the rx side...
Both the resistances are in parallel.
And regarding ground...I am using the GND pin provided on the tiva board.

Instead of tm4c123 on the rx side, I am using tm4c129 with PB0 and PB1 of CAN1 module.

Hello Ninad,

Is the GND common between the two boards?

Regards
Amit

Yes Amit,
i have connected the GND pins on both the boards together.

At this level - would not your CAN Communication be made so much simpler & faster by confining both boards to TM4C123. Any "CAN differences" (w/in software, MCU set-up/config) between 123 & 129 tend to "get in the way" - thus confound - your CAN objective.

KISS argues for the simplest methods (always) to begin - followed by expansion and/or refinement only after "basics" have been achieved...

Hey cb1_mobile,
Thank you for your valuable suggestion.
I will try to implement this once the second tm4c123 board arrives next week.
Till then, can you help me troubleshoot what is causing the "cable connected error" on the tx side which is using the tm4c123 board and mcp2551 as the transceiver.
For the puTTy terminal, i am entering the baud rate as 115200.
Has that got anything to with this?

Hello Ninad,

Can you please attach the code for the TM4C123 and TM4C129 devices for inspection to see if there is something other than the transceiver.

Regards
Amit

Hey Amit,
Got the new TM4C123G board today,
tried the same setup.
The communication is happening, but the puTTy terminal on the transmitter side is blank whereas on the receiver side it is displaying the message received as well as the incremented count.
The PC on which the receiver is connected is running windows 7 and the transmitter PC is running windows 10.

Thanks in advance.
Ninad

Hello Ninad

Can you check the drivers in Device Manager of Windows 10?

Regards
Amit

Hey Amit,
I tried connecting both the boards to the same system running windows 7, but the same problem is springing up,

The transmitter puTTy window shows nothing, it is blank, but the receiver puTTy window is correctly displaying the messages that are being received.

Please help.

Hello Ninad,

Did you check if there are 2 COM ports being shown in the device manager?

Regards
Amit