Opinions on LIN

I'm looking at short-haul comm protocols. LIN seems to fit my needs. One-wire is especially attractive. Anyone have any suggestions in this regard?

Thanx, Doug

Reply to
Doug Dotson
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Saving one wire against RS232 means the protocol knows when to switch the direction or the message length is fixed. Is saving one wire really that attractive ?

Rene

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Reply to
Rene Tschaggelar

What length is short-haul ? Is it between PCBs, between adjascent boxes ? Anyway I have been looking at LIN myself, and for what it is designed it looks quite nice. At the moment there are very few proper LIN slave devices which is not a MCU + LIN Driver. So ATM if you are going to connect two or more MCUs together then the more traditional UART, SPI, I2C or CAN might be a better option.

Regards Anton Erasmus

Reply to
Anton Erasmus

This is not point-to-point communications. I thought about using RS-485 but that takes 4 wires for full-duplex. 2-wire is half-duplex so I might as well go 1-wire with LIN. Another limitation I am facing is the I/O capabilities of the uP I am using. With only 5 I/O pins, an extra pin for full-duplex comms does become a potential issue.

Doug

Reply to
Doug Dotson

Probably not more than 100 feet. If it were between PCBs than I would probably use I2C or SPI.

There is code for the ATMEL chips that implement LIN driectly on a single pin. Using an external driver such as the MC33399 requires multiple pins and with only 5 I/O pins on the chip I plan to use, that becomes an issue.

Reply to
Doug Dotson

LIN bus has been designed for in-car use, hence I do not think you are going to get 100 feet. Having said that it, is basically a half-duplex protocol that can be implimented using a normal UART + suitable driver. One can probably impliment the LIN bus protocol using a RS-485 driver. This will easily do the 100 feet, although you will need 2 wires (plus GND). With this you still only need one MCU pin for the half-duplex protocol. The one-wire bus from DALLAS/Maxim can do long distances and can also be done in software, although the timing restrictions are more severe than for the LIN Bus protocol.

Regards Anton Erasmus

Reply to
Anton Erasmus

Comments below.

Doug

Ya think! Obviously I'm not planning on using it for a car.

I suppose so.

Perhaps, but the LIN spec describes the line characteristics. RS-485 doesn;t seem to comply.

But this isn't LIN.

But this isn;t LIN. Perhaps I wasn;t clear. Tell me about the pros and cons of LIN. I know of numerous ways of communicating. I'm asking about LIN.

Reply to
Doug Dotson

Actually the LIN spec is 40 meters max.

Reply to
Doug Dotson

On Tue, 10 Aug 2004 17:36:33 -0400, "Doug Dotson" wrote:

OK. AS I understand it LIN Bus was designed to be a sub bus to very cheaply connect sensors to a local CAN Bus node. I.e. one can use a US$15 MCU for the CAN bus node, and to connect sensors and outputs such as switches and lights to this node one uses LIN bus. The LIN slave can be a cheap 1-5US$ MCU or an IC designed as a LIN slave. Currently there are only a few dedicated LIN slave ICs I have found. There are a few to drive LEDs (Including programmable PWM for brightness). Once there are many dedicated LIN slave ICs, it would be quite a nice and cheap solution in many cases. ATM for most things one need to use an MCU for the LIN Bus master as well as a MCU for the slave - hence currently there is not much advantage in using LIN bus in stead of the more traditional approaches. For the high volumes used in the motor car industry the difference in pricing between the CAN MCUs and non CAN MCUs are significant. For lower volumes the price difference are insignificant. For many of the projects I work on - using a US$50 MCU will still make sense if I can save a week or two in development time. The full LIN Bus specification provides a way for the software to configure itself to handle similar types of devices from different manufacturers in a transparent way. So if you have a module that senses a door switch provided by Bosch - one can replace it with a switch sensor provided by BMW without having to change any of the software. I think the idea is to start with MCU based slaves, and then gradually replace these devices with dedicated slaves. This can then be retrofitted to older models without problems.

My 2c worth.

Regards Anton Erasmus

Reply to
Anton Erasmus

Thanks Anton,

This helps alot. I have been looking at MicroMessaging and noticed the relation between LIN and CAN.

Doug

Reply to
Doug Dotson

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