Forums

CANbus driver

Started by Francois October 10, 2002
Hi,

What will be a simple CAN bus driver. Can I just connect a half duplex
multi-drop RS485 driver to the
TX and RX pins. How does the DP256 CAN handle the TX enable of a RS485 chip
for instance. I suppose that a isolated configuration is possible with a one
wire current loop configuration. Any ideas.

Frank van der Merwe




Hi,

What will be a simple CAN bus driver. Can I just connect a half duplex
multi-drop RS485 driver to the
TX and RX pins. How does the DP256 CAN handle the TX enable of a RS485 chip
for instance. I suppose that a isolated configuration is possible with a
one
wire current loop configuration. Any ideas.

Frank van der Merwe



In the early days of CAN we used to use the RS-485 drivers
by wiring the txenable pin to the CAN TX pin. I guess the
question would be, why not just use the available, and better
suited, CAN tranceivers that are available?

Steve

Zanthic Technologies Inc. is located at www.zanthic.com
Your Controller Area Networking Experts!
Embedded micro-controllers and CAN interface devices sold here

----- Original Message -----
From: Francois
To:
Sent: Thursday, October 10, 2002 10:36 AM
Subject: [68HC12] CANbus driver

Hi,

What will be a simple CAN bus driver. Can I just connect a half duplex
multi-drop RS485 driver to the
TX and RX pins. How does the DP256 CAN handle the TX enable of a RS485 chip
for instance. I suppose that a isolated configuration is possible with a
one
wire current loop configuration. Any ideas.

Frank van der Merwe

--------------------
">http://docs.yahoo.com/info/terms/


Hi,

I am basically looking or the cheapest and practical implementation. There
is the MC33388 which I assume takes care of "muting the TX driver " - I
just trying to avoid specalty parts that might go out of scope and does not
have a second source.

How about a open collector arrangement using RS485 drivers, with a wired orr
configuration on the buss.
So any slave can engage the buss. I guess that if it is open collector
driven with pullups, then there is no need to "mute" the transmitter.
However I am not sure of the loopback issues - any clues allong this
simplified implementation - im not an expert on CAN.

What other drivers are available similar to the MC33388??

Frank van der Merwe ----- Original Message -----
From: "Steve Letkeman" <>
To: <>
Sent: Thursday, October 10, 2002 10:32 AM
Subject: Re: [68HC12] CANbus driver > In the early days of CAN we used to use the RS-485 drivers
> by wiring the txenable pin to the CAN TX pin. I guess the
> question would be, why not just use the available, and better
> suited, CAN tranceivers that are available?
>
> Steve
>
> Zanthic Technologies Inc. is located at www.zanthic.com
> Your Controller Area Networking Experts!
> Embedded micro-controllers and CAN interface devices sold here
>
> ----- Original Message -----
> From: Francois
> To:
> Sent: Thursday, October 10, 2002 10:36 AM
> Subject: [68HC12] CANbus driver >
>
> Hi,
>
> What will be a simple CAN bus driver. Can I just connect a half duplex
> multi-drop RS485 driver to the
> TX and RX pins. How does the DP256 CAN handle the TX enable of a RS485
chip
> for instance. I suppose that a isolated configuration is possible with
a
> one
> wire current loop configuration. Any ideas.
>
> Frank van der Merwe >
>
> -------------------- >
> ">http://docs.yahoo.com/info/terms/
> -------------------- >
> ">http://docs.yahoo.com/info/terms/




How about a 82C250 or SI9200 CAN transceiver, about the same price 8 pin SO
Dale Kelley

-----Original Message-----
From: Francois [mailto:]
Sent: Thursday, October 10, 2002 11:54 AM
To:
Subject: [68HC12] CANbus driver Hi,

What will be a simple CAN bus driver. Can I just connect a half duplex
multi-drop RS485 driver to the
TX and RX pins. How does the DP256 CAN handle the TX enable of a RS485 chip
for instance. I suppose that a isolated configuration is possible with a one
wire current loop configuration. Any ideas.

Frank van der Merwe
--------------------
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If you have received it in error, please notify the sender
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you can run a CAN bus on a limited size network using a simple wired OR
configuration but it wouldn't be practical for leaving the board any distance.
There are standard devices like the 82C250 mentioned that have pinouts
that are duplicated by a number of devices by a number of manufacturers,
so I don't think you have to worry about them not being available.
The idea behind CAN is that each transceiver sees it's own driven level
on the bus and everybody else's also. If the local node is in a non-dominant
state and another node is dominant than the local node backs off because
it lost arbitration. The lower the CAN ID, the higher the priority and the
more chance it gets through over the lower priority message. (this is the
simplified version)

Steve Hi,

I am basically looking or the cheapest and practical implementation. There
is the MC33388 which I assume takes care of "muting the TX driver " - I
just trying to avoid specalty parts that might go out of scope and does not
have a second source.

How about a open collector arrangement using RS485 drivers, with a wired orr
configuration on the buss.
So any slave can engage the buss. I guess that if it is open collector
driven with pullups, then there is no need to "mute" the transmitter.
However I am not sure of the loopback issues - any clues allong this
simplified implementation - im not an expert on CAN.

What other drivers are available similar to the MC33388??

Frank van der Merwe ----- Original Message -----
From: "Steve Letkeman" <>
To: <>
Sent: Thursday, October 10, 2002 10:32 AM
Subject: Re: [68HC12] CANbus driver > In the early days of CAN we used to use the RS-485 drivers
> by wiring the txenable pin to the CAN TX pin. I guess the
> question would be, why not just use the available, and better
> suited, CAN tranceivers that are available?
>
> Steve
>
> Zanthic Technologies Inc. is located at www.zanthic.com
> Your Controller Area Networking Experts!
> Embedded micro-controllers and CAN interface devices sold here
>
> ----- Original Message -----
> From: Francois
> To:
> Sent: Thursday, October 10, 2002 10:36 AM
> Subject: [68HC12] CANbus driver >
>
> Hi,
>
> What will be a simple CAN bus driver. Can I just connect a half duplex
> multi-drop RS485 driver to the
> TX and RX pins. How does the DP256 CAN handle the TX enable of a RS485
chip
> for instance. I suppose that a isolated configuration is possible with
a
> one
> wire current loop configuration. Any ideas.
>
> Frank van der Merwe >
>
> -------------------- >
> ">http://docs.yahoo.com/info/terms/
> -------------------- >
> ">http://docs.yahoo.com/info/terms/
--------------------
">http://docs.yahoo.com/info/terms/


IMHO you should very seriously consider just using a bus driver designed for CAN.
There are a number of features built-in that you can take advantage of
that would not be present in an RS485 chip set--even if you figured out
a way to deal with bus arbitration. (Have you read up on that yet?)

The original 82C250 from Philips is the classic device, and Philips
has some replacement devices too. There's the Motorola MC33388.
TI makes an SN65LBC031, which is sold in DigiKey. There are a
number of others, too.

You should have absolutely no fears about there not being a source of
CAN bus drivers. There are tens of millions of CAN nodes every year
in the automotive market alone. CAN is becoming more prevalent
in automotive, not less.

There are many hundreds of thousands of CAN nodes every year
in industrial control applications too--such as DeviceNet.

Best regards,

Kerry Berland

Silicon Engines
2101 Oxford Road
Des Plaines, IL 60018 USA
847-803-6860
Fax 847-803-6870

----- Original Message -----
From: Francois
To:
Sent: Thursday, October 10, 2002 1:05 PM
Subject: Re: [68HC12] CANbus driver Hi,

I am basically looking or the cheapest and practical implementation. There
is the MC33388 which I assume takes care of "muting the TX driver " - I
just trying to avoid specalty parts that might go out of scope and does not
have a second source.

How about a open collector arrangement using RS485 drivers, with a wired orr
configuration on the buss.
So any slave can engage the buss. I guess that if it is open collector
driven with pullups, then there is no need to "mute" the transmitter.
However I am not sure of the loopback issues - any clues allong this
simplified implementation - im not an expert on CAN.

What other drivers are available similar to the MC33388??

Frank van der Merwe ----- Original Message -----
From: "Steve Letkeman" <>
To: <>
Sent: Thursday, October 10, 2002 10:32 AM
Subject: Re: [68HC12] CANbus driver > In the early days of CAN we used to use the RS-485 drivers
> by wiring the txenable pin to the CAN TX pin. I guess the
> question would be, why not just use the available, and better
> suited, CAN tranceivers that are available?
>
> Steve
>
> Zanthic Technologies Inc. is located at www.zanthic.com
> Your Controller Area Networking Experts!
> Embedded micro-controllers and CAN interface devices sold here
>
> ----- Original Message -----
> From: Francois
> To:
> Sent: Thursday, October 10, 2002 10:36 AM
> Subject: [68HC12] CANbus driver >
>
> Hi,
>
> What will be a simple CAN bus driver. Can I just connect a half duplex
> multi-drop RS485 driver to the
> TX and RX pins. How does the DP256 CAN handle the TX enable of a RS485
chip
> for instance. I suppose that a isolated configuration is possible with
a
> one
> wire current loop configuration. Any ideas.
>
> Frank van der Merwe >
>
> -------------------- >
> ">http://docs.yahoo.com/info/terms/
> -------------------- >
> ">http://docs.yahoo.com/info/terms/


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