RS485 full duplex mode using MAX485 and programming in atmega8

Go To Last Post
13 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

can anyone help me with RS485  full duplex , i want to communicate two atmega8 (transmiting and receiving) with max485, 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Go on.

 

RS485 has been around for decades - can you really find nothing in any reference books, or on the interwebs?

 

What about the MAX485 datasheet? Surely, Maxim have application notes ?

 

https://en.wikipedia.org/wiki/RS-485

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

https://www.avrfreaks.net/commen...

 

Did you check this out?

 

Jim

Click Link: Get Free Stock: Retire early! PM for strategy

share.robinhood.com/jamesc3274

 

 

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

OK, I'm just an old bit-pusher, but isn't "RS485 full duplex" an oxymoron?  Isn't RS485 inherently half-duplex?  Did you mean RS422?

 

Now, how will I verify this?  A simple Google search perhaps?

 

I stand corrected, by myself ans Wikipedia:

Full duplex operation

RS-485, like RS-422, can be made full-duplex by using four wires. Since RS-485 is a multi-point specification, however, this is not necessary in many cases. RS-485 and RS-422 can interoperate with certain restrictions.

But still, an "impossible question" IMO. 'Have you stopped beating your wife yet?  Answer yes or no.'

 

https://www.imdb.com/title/tt010...

My Cousin Vinny (1992)

Quotes

D.A. Jim Trotter: Now, uh, Ms. Vito, being an expert on general automotive knowledge, can you tell me... what would the correct ignition timing be on a 1955 Bel Air Chevrolet, with a 327 cubic-inch engine and a four-barrel carburetor?

Mona Lisa Vito: It's a bullshit question.

D.A. Jim Trotter: Does that mean that you can't answer it?

Mona Lisa Vito: It's a bullshit question, it's impossible to answer.

D.A. Jim Trotter: Impossible because you don't know the answer!

Mona Lisa Vito: Nobody could answer that question!

D.A. Jim Trotter: Your Honor, I move to disqualify Ms. Vito as a "expert witness"!

Judge Chamberlain Haller: Can you answer the question?

Mona Lisa Vito: No, it is a trick question!

Judge Chamberlain Haller: Why is it a trick question?

Vinny Gambini: [to Bill] Watch this.

Mona Lisa Vito: 'Cause Chevy didn't make a 327 in '55, the 327 didn't come out till '62. And it wasn't offered in the Bel Air with a four-barrel carb till '64. However, in 1964, the correct ignition timing would be four degrees before top-dead-center.

D.A. Jim Trotter: Well... um... she's acceptable, Your Honor.

 

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Now you'll just have to explain what "ignition timing" is for the kiddies who've known nothing but computer-controlled cars ...

 

frown

 

You'll be expecting them to know what a "choke" is next ...

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

awneil wrote:
You'll be expecting them to know what a "choke" is next ...

A choke is useful in certain situations; e.g.

Image result for never give up

I'm so old that the first farm pickup trucks I drove had not only hand choke knobs, but hand throttle (overriding the foot pedal) as well.

Image result for '64 chevy pickup truck dashboard

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

theusch wrote:
the first farm pickup trucks I drove had not only hand choke knobs, but hand throttle (overriding the foot pedal) as well. Image result for '64 chevy pickup truck dashboard

And just in case anyone asks, the hand throttle allows one person to enter a field, set a slow speed, leave the cab and from the bed of the truck, rake hay out to the cows! (Yes, no driver!)

My father-in-law still complains to this day about modern trucks with out that feature!

 

Jim

 

Click Link: Get Free Stock: Retire early! PM for strategy

share.robinhood.com/jamesc3274

 

 

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

ki0bk wrote:
My father-in-law still complains to this day about modern trucks with out that feature!

I guess, in the not-too-distant future, it will be kind of back - as the truck will drive itself!

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I answered this question in your other thread. Go look there.

And what makes you think this will be any easier?

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Here: https://www.avrfreaks.net/forum/rs485-avr-communication-master-and-slave

 

Having spent over 50 posts there to understand multiple slave addressing, it was also pointed out that it won't work with full duplex!

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

ki0bk wrote:
And just in case anyone asks, the hand throttle allows one person to enter a field, set a slow speed, leave the cab and from the bed of the truck, rake hay out to the cows! (Yes, no driver!) My father-in-law still complains to this day about modern trucks with out that feature!

[Remembering that this was all 50 or so years ago...] In looking for the photo above and doing Google searches, I read that in that time [early '60s] that Chevy C10 pickup trucks did NOT have the hand-throttle feature.  Some dashboards had a spot that could be cutout for it.

 

But the model that we had was a heavy-duty model with 10-ply tires and similar, and the feature was often found on these commercial/industrial trucks that had a power takeoff. 

 

And "of course" the 1944 International pickup and 1951 Chevy pickup had the feature.

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly