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'CAN bus anyone?'
1998\12\15@090525 by Aschwin Gopalan

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Dear PIClisters!

Has anybody used a PIC to connect to a CAN bus and is willing to share
experiences? What driver, does it work at all etc...

My application is a science device which will have a computer connected
to several (maybe 20) devices for data aquisition and control. Speed is
not too important and the distance between the devices is small (about 4m max.)

Or should I go for RS-485? Are there any standard protocols for addressing
etc?

Or maybe I2C?

Well, I am thankful for any advice...

Bye and happy PICin«,

Aki

1998\12\15@091151 by Harrison Cooper

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I just read....in one of the trade magazines (EET?), that Microchip will be
coming out with a CAN micro...anyone else heard or seen that one? I have yet
to look for it on thier web site

{Quote hidden}

1998\12\15@114844 by keller

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I have never developed anything for CAN bus but I have looked in to it.
Philips and Seimens make add on CAN controller chips but I still think it
requires a lot of program overhead.  Philips makes a stand alone controller
with some A/D and digital inputs and outputs that sits directly on the CAN
bus without the need for the processor.  I have never done anything with
them only read the data sheet.   For the price there is quite a bit of
manufactured CAN modules that are fairly priced.  Check out
http://www.devicenet.org for different manufactures.

I think Microchip is working on a controller with CAN built in but don't
know when, or if, it will be available.

Steve

{Original Message removed}

1998\12\15@130736 by Darren Logan

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Go for RS485, very easy and cheap to implement.
RS485 is RS232 but with differential signals over 1200 mtrs or so.

RS485 chips are ~ £2.0 only.

Design your own protocol. I did.

Darren

1998\12\15@151130 by Morgan Olsson

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At 10:46 1998-12-15 -0600, you wrote:
>I have never developed anything for CAN bus but I have looked in to it.
>Philips and Seimens make add on CAN controller chips but I still think it
>requires a lot of program overhead.  Philips makes a stand alone controller
>with some A/D and digital inputs and outputs that sits directly on the CAN
>bus without the need for the processor.  I have never done anything with
>them only read the data sheet.

Same here.
I heard however that they (called SLIOs) will be discontinued.

There are some microcontroller for about that price too that have CAN
built-in, at least one COP microcontroller, a 6805, and probably some 6808
and 6811.

For more computer there are Siemens 515 or something, or some 68xxx with
dual CAN if I remember correctly.

>  For the price there is quite a bit of
>manufactured CAN modules that are fairly priced.  Check out
>http://www.devicenet.org for different manufactures.
>
>I think Microchip is working on a controller with CAN built in but don't
>know when, or if, it will be available.

They are stupid if they wait too long.
CAM market is growing rapidly.

>Steve

       Morgan Olsson                   ph  +46(0)414 70741
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___________________________________________________________

1998\12\15@171517 by Jason Tuendemann

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I did see something on this a while ago. There were infact some prelimenary
docs on the microchip web site, it was a 17 series chip.

Jason




I just read....in one of the trade magazines (EET?), that Microchip will be
coming out with a CAN micro...anyone else heard or seen that one? I have yet
to look for it on thier web site

{Quote hidden}

1998\12\15@175728 by evan

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> For more computer there are Siemens 515 or something, or some 68xxx with
> dual CAN if I remember correctly.

Motorola 68376 has a nice CAN module built in.

-Ed V.
Agile Controls

1998\12\16@055701 by Vadim

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Hi,
Immediately beg pardon for english - translates a wife, which nothing does
not understand in the electricity.
I used max232 + sn75176 for the relationship COM-a port with 14 controllers
on pic84 on velocities 9600 and 19200 bps on the distance 250 metres.
Protocol of exchange has stolen from the cash device:
1 word - "AAh" - start
2 - amount a byte in frame (N)
3 - command
4 - address of device
5 - sent given ( if command - record )
.....
N - inv control total of all bytes.

Callable controller will send a byte "OK" - 5Ah or not - "OK" - A5h or
nothing. Hereinafter - executes a command. Back, issue goes in same type.
If received not - "OK" or no answer, repetition of issue else 3 times.
Controllers work at the street, not switching off more.

Willingly divide lifelengths on pic84

VADIM vadspamspam_OUTanet.lv

1998\12\16@112406 by Eugene Skopal

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Aschwin,

A RS-485 solution will be a LOT less expensive.  Take a look at SAE J1708
for a suitable design.  Read http://www.national.com's AN-915 "Automotive Physical
Layer SAE J1708 and the DS36277" for the pertinent information.

Unfortunatly, you will have to spend $49 to download the actual standard
from the SAE site -- but it does give you a head-start on your project.

..Eugene..

{Original Message removed}

1998\12\16@122655 by AE2F

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Aschwin,

A RS-485 solution will be a LOT less expensive.  Take a look at SAE
J1708
for a suitable design.  Read http://www.national.com's AN-915 "Automotive
Physical
Layer SAE J1708 and the DS36277" for the pertinent information.

Unfortunatly, you will have to spend $49 to download the actual standard
from the SAE site -- but it does give you a head-start on your project.

..Eugene..

{Original Message removed}

1998\12\17@000540 by Tjaart van der Walt

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Morgan Olsson wrote:
>
> At 10:46 1998-12-15 -0600, you wrote:
> >I have never developed anything for CAN bus but I have looked in to it.
> >Philips and Seimens make add on CAN controller chips but I still think it
> >requires a lot of program overhead.  Philips makes a stand alone controller
> >with some A/D and digital inputs and outputs that sits directly on the CAN
> >bus without the need for the processor.  I have never done anything with
> >them only read the data sheet.
>
> Same here.
> I heard however that they (called SLIOs) will be discontinued.
>
> There are some microcontroller for about that price too that have CAN
> built-in, at least one COP microcontroller, a 6805, and probably some 6808
> and 6811.

There is a Fujitsu with 3 CAN busses. The part price wasn't
bad, but the emulator price was crazy, so we dropped that idea.

--
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1998\12\17@103304 by Vadim

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face
Hi,
Beg Pardon for english - not my native language.

I used max232 + sn75176 for the relationship COM-a port with 14
controllers
on pic84 on speed 9600 and 19200 bps on the distance 250 metres.
Protocol of exchange has stolen from the cash device:
1 word - "AAh" - start
2 - amount a byte in frame (N)
3 - command
4 - address of device
5 - sent data ( if command - record )
......
N - inv control total of all bytes.

Callable controller will send a byte "OK" - 5Ah or not - "OK" - A5h or
nothing. Hereinafter - executes a command. Back, issue goes in same
type.
If received not - "OK" or no answer, repetition of issue else 3 times.
Controllers work at the street, not switching off more.

Willingly divide lifelengths on pic84

VADIM RemoveMEvadTakeThisOuTspamanet.lv

1998\12\17@124940 by Eugene Skopal

flavicon
face
Aschwin,

A RS-485 solution will be a LOT less expensive.  Take a look at SAE
J1708 for a suitable design.  Read http://www.national.com's AN-915 "Automotive
Physical Layer SAE J1708 and the DS36277" for the pertinent information.

Unfortunatly, you will have to spend $49 to download the actual standard
from the SAE site -- but it does give you a head-start on your project.

..Eugene..

{Original Message removed}

1998\12\29@160136 by John Payson

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|Has anybody used a PIC to connect to a CAN bus and is willing to share
|experiences? What driver, does it work at all etc...

One problem (IMHO) with CAN as opposed to I2C is that the clock
is always generated by whatever device is transmitting, as opposed
to being always generated by the master.  While multi-master I2C
communications are difficult, the single-master case is very common
and there are practically no timing restrictions on the master dev-
ice.  By contrast, CAN requires that the master device be able to
accept data whenever it arrives; without dedicated hardware that is
going to be very difficult.

As others here have suggested, asynchronous communications (RS-485
or other) can be much cheaper to work with; many PICs have UARTs
built-in, so receiving data at the time the remote device chooses
to send it should not be a problem.  If you control the software in
the remote devices, you may be able to make the master's job esp-
ecially easy if you make the remotes sync their bit clock off the
master's (pref. with a half-bit delay).

As a simple example to illustrate the concept, imagine that you
have a master with up to 255 remote units, and the protocol consists
simply of the master sending out the unit number of a slave and that
slave sending back its data, with a minimum of 10 bit times' idle
line following the transaction before the next one begins.  Assume
a data rate of 9600bits/second.

The main loop of a slave consists of reading its A/D (or whatever)
while checking to ensure the comm. line is idle, waiting for the
remainder of 10 bit times, and then going into a busy-wait looking
for the master to say something.  If the master outputs something
other than the device's address, the device restarts the main loop.
Otherwise, the device waits 1/2 bit time after the master's stop
bit and outputs a byte of data.  After that, it restarts the main
loop.

>From the master's perspective, all it has to do is have a 9600Hz
routine which outputs the desired address and then reads the data
return for the next nine bit times.  If the start bit (1st bit time)
is not present, the transaction failed.  Otherwise the data will be
as it should be.  Note that the master knows exactly when everything
is going to happen and the slaves are simply busy-waiting for the
master any time they might be addressed.  Both the master and slave
code can be very simple even on PICs without hardware UARTs or even
interrupts.

Fancy bus protocols like I2C and CANbus are good for multi-master
situations, but for single-master situations they are often over-
kill.  I2C simplifies nicely in the single-master case.  Too bad
some other protocols don't.


'CAN bus anyone?'
1999\01\01@234603 by aab
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>Has anybody used a PIC to connect to a CAN bus and is willing to share
>experiences? What driver, does it work at all etc...

You might try the CAN mailing list. Archives at
http://www.scruz.net/~cichlid/can-archive. Subscribe instructions
at http://www.scruz.net/~cichlid/archives.html

--
Andrew Burgess
spamBeGoneaabspamBeGonespamcichlid.com
Available for software contract work: http://www.scruz.net/~cichlid

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