Hello all, here to try to pick the brains of any Microchip MCP2510 CAN
Controller users...

I'm currently trying to get a simple packet sent, and have the 2510
cause a recieve interrupt.  For the life of me I can't get it to
happen...  I've followed 3 app notes, several code on the web and it
just will not occur (by itself).  Not even the transmit interrupt.

I'm using it in loopback mode.  I have some PCA82C250's here but I want
to simplify before going that route.  I have all the filters off, set to
recieve any message.

I can cause it to happen by writing 1 to any of the enabled interrupt
flags, INT then goes low and my ISR executes just fine.

I know my SPI writes to the chip are working as I can change a 2510's
pin to a GPO and flash an LED with it.  I've used it to test my byte
write, bit modify, and my read instructions...

Using these I follow this simple sequence (I hope my macro-ized code is
fairly explanitory):

---------------------------------------------

  MCP2510_RESET                                 ; reset the chip (as per
datasheet)
  DELAY_MICRO 25                                        ; let it reset
  MCP2510_WRITE CNF1, 0x09                      ; from program
  MCP2510_WRITE CNF2, 0x90                      ; from program
  MCP2510_WRITE CNF3, 0x02                      ; from program
  MCP2510_WRITE RXB0CTRL, 0x60          ; recieve all msgs
  MCP2510_WRITE RXB1CTRL, 0x60          ; recieve all msgs
  MCP2510_WRITE CANCTRL, 0x44                   ; Loopback Mode, CLKOUT
disabled

  MCP2510_WRITE CANINTF, 0x00                   ; clear interrupt flags
  MCP2510_WRITE CANINTE, 0x0F                   ; enable interrupts

  DELAY_MILLI 250                                       ; wait a while
so human eyes can see stuff happen

  clrf PIR1                                             ; clear out
interrupt flags
  bsf INTCON, INTE                              ; enable INT interrupt
  bsf INTCON, GIE                                       ; enable
interrupts

; build a packet

  MCP2510_WRITE TXB1SIDH, 0xAC
  MCP2510_WRITE TXB1SIDL, 0x40          ; standard identifier

  MCP2510_WRITE TXB1DLC, 0x04

  MCP2510_WRITE TXB1D0, 0xAA
  MCP2510_WRITE TXB1D1, 0xBA
  MCP2510_WRITE TXB1D2, 0xAF
  MCP2510_WRITE TXB1D3, 0x5B

  MCP2510_RTS TXB1                              ; send it

------------------------

I've tried this with TXB0 as well.  Afterwards it just goes to a "goto
$" loop and is ISR from then on out...

I have every basic I/O interrupt enabled on the MCP2510.  I have tried
it with the ERROR interrupts enabled as well, with nothing happening so
I don't think something is happening incorrectly during the transfer.

I've also tried setting the TX bit, and not using the RTS command...

So the moral of the story is, I can get the ISR to run on my 16F876
manually by dropping the INT line, but the MCP2510 won't do it
automagically...

Ideas?  Sample code?

Thanks!

nick@veys.com | www.veys.com/nick

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