Problem with Interfacing MCP2515 CAN Controller and PIC18F4520

[Naren Rover]

Hi, guys I'm working with MCP2515 CAN Module and PIC18F series.I write a single byte data and read it back using SPI Protocol.
But I am unable to receive any data back.
here i have posted the code please check it and help me.
i connected two MCP2525 modules , so I think there is no problem with Hardware
( 1 from local vendor and other from Ali express).
I don't have any oscilloscope
Thank you.

 

[Ian Rogers]

So two Modules!! Both have a CS pin.. I'm trying to see where you differentiate between the two MCP modules.. Sending on one then receiving on the other.

 

[Naren Rover]

Actually , No i'm using 1 module only, I had another one lying around , so i removed this one and hooked that one up just to make sure if IC was damaged, but i did not get anything from that also.
1 MCP2515 connected with PIC18F to send a CAN Message which will be received by PEAK CAN and will be displayed in Monitor.
I'm in initial step of development , trying to" communicate with MCP2515 and PIC18F" , which i'm not successful.
I'm at it for 2 days and it's really frustrating.
Thank you.

 

[Nigel Goodwin]

Do you have the SPI configured correctly?, is it set to the correct type of SPI?.

 

[Ian Rogers]

Okay!! I think you should read up on canbus! Its not like simple SPI, it works with frames... You cannot just send a byte.. You need to think of it like a letter... You won't get a response if there is no address on the front... Check canbus on wiki.. If it were pic to pic then you could possible do without a protocol but peak can will require a frame...( I think there are led indicators to show activity, but that's about it ).

 

[rjenkinsgb]

See the application note here, for a simple setup using an MCP2515 with a PIC18 series CPU.
It includes source code examples.

https://ww1.microchip.com/downloads/en/AppNotes/00212c.pdf

 

[Naren Rover]

Do you have the SPI configured correctly?, is it set to the correct type of SPI?.

Yes i did, the data sheet says that either Mode 0,0 or 1,1 to be used and maximum speed at 10 MHz , I'm using Mode 0,0 and Speed Fosc/64 i.e., 312KHz

 

[Naren Rover]

Okay!! I think you should read up on canbus! Its not like simple SPI, it works with frames... You cannot just send a byte.. You need to think of it like a letter... You won't get a response if there is no address on the front... Check canbus on wiki.. If it were pic to pic then you could possible do without a protocol but peak can will require a frame...( I think there are led indicators to show activity, but that's about it ).

I think my question was misunderstood.
I have not yet started CAN programming
All i'm trying to is , communicating between PIC and MCP
i write a register in MCP using SPI protocol and Reading it back to see if the communication is successful
Im not getting anything from MCP . All Im getting is 0x00.
I need you guys to see if my program is correct or did i make any mistakes

 

[Ian Rogers]

I don't think you can. The byte will be sent to a tx register buffer and isn't available to be read back.. Use my original misunderstanding.. use both MCP chips and send and receive that way... Like we do for rs232 testing...

 

[Naren Rover]

i have attached the MCP 2515 data sheet. I'm not talking about CAN transmit - receive message.
All I'm trying to do is to check if there is a communication between MCP and my PIC board that's all
There is register called CAN Control register(as shown in the uploaded .jpg file) , which is to written by the PIC controller to set it in different modes.
CAN Control register is READ/WRITE Register. with address 0x0F
I'm writing 0x80 to the register setting it in "Configuration mode ".
and reading it back from CAN_Status_Reg , which has address 0x0E
to see if my command was recieved from PIC.
but I'm getting 0x00;

i don't know if the problem is in my coding or someother thing.
that's why i need you guys to help me

 

[Naren Rover]

Do you have the SPI configured correctly?, is it set to the correct type of SPI?.

Thanks guys i found the mistake, it was with SPI mode selection. i data sheet it was said Mode 0,0 , so i thought Clock phase and polarity to be Zero, which was not like that when i read the data sheet again.
Now i'm able to read and write it back.

if possible I'll upload a Basic transmit receive code for MPC2515 in C language.
Thank you

 

[Nigel Goodwin]

Thanks guys i found the mistake, it was with SPI mode selection.

I spent weeks trying to get SPI to work again, after I lost all my previous code - and it was all down to the wrong mode

 

[Naren Rover]

I spent weeks trying to get SPI to work again, after I lost all my previous code - and it was all down to the wrong mode

Because of you was able to find it easily, Thank you

 

[dr pepper]

I had an issue trying to get a mcp25xx module to work too, I was using a non standard bitrate because the deafult xtal frequency in the lib I was using wasnt the xtal freq in my modules.