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Sterngleiter
Joined: 07 Jan 2013
Posts: 90
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| Can Bus PIC18f45k80 |
 Posted: Mon Dec 31, 2018 9:43 am |
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Hello, I use pic18f45k80 and pcwhd 5.070.
I would like to send and receive only.
Here is my code.
transmitter:
| Code: |
#include <can-18xxx8.c>
void main ( )
{
int32 rx_id=0;
int rx_len,rxstat,buffer[8];
int1 a,b;
int buf;
can_init ( );
//wait for node c to power-up
while ( TRUE )
{
if (input(pin_b4)==1)
{
while (input(pin_b4)==1);
while (!can_putd(0x456, buffer, 2, 1, TRUE, FALSE)) {}
buffer[0]=0x07;
buffer[1]=0x70;
buffer[2]=0;
buffer[3]=0;
buffer[4]=0;
buffer[5]=0;
buffer[6]=0;
buffer[7]=0;
}
if (input(pin_b1)==1)
{
while (input(pin_b1)==1);
while (!can_putd(0x200, buffer, 2, 1, TRUE, FALSE)) {}
buffer[0]=0x07;
buffer[1]=0x44;
buffer[2]=0;
buffer[3]=0;
buffer[4]=0;
buffer[5]=0;
buffer[6]=0;
buffer[7]=0;
}
}
}
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receiver:
| Code: |
#include <can-18xxx8.c>
void set_my_can_filters(void);
#define xyz 0x456
int32 rx_id=0;
struct rx_stat stat;
int8 rx_len,buffer[8];
#INT_CANRX0
void CANRX0_isr(void)
{
// output_d(1);
can_getd ( rx_id , &buffer , rx_len , stat );
if( rx_id == xyz&&buffer[0]==0x07)
{
output_d(buffer[1]);
rx_id=0;
buffer[1]=0;
}
if (rx_id==0x200){rx_id=0;}
}
void main ( )
{
enable_interrupts(INT_CANRX0);
enable_interrupts(INT_CANRX1);
enable_interrupts(GLOBAL);
can_init ( );
set_my_can_filters();
//wait for node c to power-up
while ( TRUE )
{
}
}
void set_my_can_filters(void) {
can_set_mode(CAN_OP_CONFIG);
can_set_id(RX0MASK, 0x07FFFFFFF, CAN_USE_EXTENDED_ID); //set mask 0
can_set_id(RX0FILTER0, 0x456, 1); //set filter 0 of mask 0
can_set_id(RX0FILTER1, 0x456, 1); //set filter 1 of mask 0
can_set_id(RX1MASK, 0x07FFFFFFF, CAN_USE_EXTENDED_ID); //set mask 1
can_set_id(RX1FILTER2, 0x456, 1); //set filter 0 of mask 1
can_set_id(RX1FILTER3, 0x456, 1); //set filter 1 of mask 1
can_set_id(RX1FILTER4, 0x456, 1); //set filter 2 of mask 1
can_set_id(RX1FILTER5, 0x456, 1); //set filter 3 of mask 1
can_set_mode(CAN_OP_NORMAL);
}
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But this is the following problem.
If I send with the address 0x456 command is executed.
Then I send the address 0x200 as expected, the receiver does nothing.
But when I ping the 0x456 send the buffer is received from the addresses 0x200 at the first send only at the second send the buffer is overwritten even though I have filter. Why?
Thanks for your help. |
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Sterngleiter
Joined: 07 Jan 2013
Posts: 90
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| Can Bus PIC18f45k80 |
| Posted: Mon Dec 31, 2018 9:46 am |
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| And one more question. It is said that in the CAN bus line each ends with 120R resistance should be switched but it does not work when I do that. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19215
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| Posted: Mon Dec 31, 2018 12:52 pm |
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| You do understand that you need external CAN transceivers?. |
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Sterngleiter
Joined: 07 Jan 2013
Posts: 90
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| Posted: Mon Dec 31, 2018 12:54 pm |
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| I use mcp2551, this is Can tranceiver. |
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Sterngleiter
Joined: 07 Jan 2013
Posts: 90
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Ttelmah
Joined: 11 Mar 2010
Posts: 19215
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| Posted: Mon Dec 31, 2018 2:23 pm |
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Not sure what you mean by the resistance being 'switched'?.
The resistors should be 120R, at each end of the bus. |
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Sterngleiter
Joined: 07 Jan 2013
Posts: 90
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| Posted: Mon Dec 31, 2018 3:21 pm |
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My problem if this resistance is used running bus is not.
Mainly I would like to know something about the first problem something, why I only on the second send, first the buffer is overwritten |
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newguy
Joined: 24 Jun 2004
Posts: 1900
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| Posted: Mon Dec 31, 2018 3:27 pm |
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| Do you have another CAN node on the bus? All CAN buses absolutely require at least two nodes, otherwise no transmissions will occur. All transmissions feature an acknowledgement time slot where any and all active nodes will actively ACK the transmission whether it is intended for the node or not. Without this active ACK, a transmitting node automatically tags the transmission as failed and will automatically retry forever. |
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Sterngleiter
Joined: 07 Jan 2013
Posts: 90
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| Posted: Mon Dec 31, 2018 3:31 pm |
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| Only the 2 first. It should send and receive, as shown above in the code is receiver and transmitter. |
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newguy
Joined: 24 Jun 2004
Posts: 1900
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| Posted: Mon Dec 31, 2018 3:44 pm |
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So you have 2 nodes (yes/no)?
Each is running the code shown above (one as transmitter, one as receiver)?
You can get one message from transmitter -> receiver, but not if the 120R terminations are in place? |
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Sterngleiter
Joined: 07 Jan 2013
Posts: 90
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| Posted: Mon Dec 31, 2018 4:51 pm |
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| Yes that is right, I don‘t need the resistor 120r. It’s receive. The problem is when i send first time with 0x200 then with 0x456 the buffer have at first from 0x200. It must have at 0x456 . Why? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Dec 31, 2018 4:55 pm |
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Do your CAN bus connections look very similar to this schematic ? (Except that both of your PICs are 18F45K80 instead of 18F258).
 |
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temtronic
Joined: 01 Jul 2010
Posts: 9097
Location: Greensville,Ontario
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| Posted: Mon Dec 31, 2018 7:27 pm |
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a hardware question.
Are you using a real xtal/2caps for the clock or the internal RC oscillator ? While I don't use CAN (too much overhead...), if it's like USB you NEED to use a real xtal /2 caps for the clock.
Jay |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19215
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| Posted: Tue Jan 01, 2019 1:32 am |
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I think there is a misunderstanding of CAN involved here.
All nodes receive/acknowledge all messages.
The ID and filters then allow the receiver to only actually 'listen' to
the messages it wants. However the message will still have been received
into the buffer.
Also I think you are misunderstanding the message ID. The ID is _not_
an 'address'. It is an identifier to specify the type of message. |
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Sterngleiter
Joined: 07 Jan 2013
Posts: 90
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| Posted: Tue Jan 01, 2019 6:20 am |
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it may be that I have misunderstood something but I've bought this "CAN Bus Development Kit" at ccsinfo.com and checked there are the resistances not synonymous in the schematics in it.
http://www.ccsinfo.com/product_info.php?products_id=CANbuskit
I use 20mhz external xtal.
I have equipped the boards. It definitely does not work when I make the 120R pure.
Or is it another bus "http://www.ccsinfo.com/product_info.php?products_id=CANbuskit" which I do not believe. Nothing in the Exercise Book.
how can I adjust the bus,
that are the correct data on the first send in the buffer. |
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