Control LCD at 1-2 meter distance from the controller with parallel communication

Hi Jack,

Our customer would like to directly connect the I/Os of the microcontroller to the parallel input of the LCD using parallel cable (1 to 2 meter) to reduce cost. He would like to know if using a buffer sufficient in this configuration, even in a noisy environment full of synchronous / asynchronous motors? 

Regards,

Danilo

Motors are very noisy, so you are likely to need differential transmission, i.e., LVDS. It would be possible to use many LVDS transmitters and receivers, but  FPD-Link makes this simpler by (de)serializing many parallel signals through a single LVDS connection.

Hi Danilo, Jack,

What's the impedance of your 2 meter transmission line? If you want any chance at a buffer working, you'll need to properly terminate the transmitter to match to the transmission line. There's some information regarding this in our FAQ here: [FAQ] What happens when I connect a logic device's output to a 50 ohm transmission line?

In a noisy environment, I would recommend something differential like LVDS to eliminate common mode noise in your digital transmissions.  You might be able to get away with a standard logic buffer, but being single ended it won't be able to filter out CM noise. Using a Schmitt-trigger input device will help some with noise, but there's a point where no simple buffer will be able to handle it.

It seems to me that saving a few cents here wouldn't be worth having to rebuild the entire system if you find out a buffer isn't good enough to handle your application's noise levels. If you can setup a realistic test and measure the noise levels, it would help in deciding what can or can't be used.

Hi Emrys and Clemens,

Thank you for your valuable feedback. Please see the comment of our customer.

I know how expensive it is to produce a PCB, especially if it has many layers. slightly increasing the cost of the PCD would lead me to prefer the use of an additional microcontroller (such as TMS320F28002x) connected to the CAN network, i.e .:
Main board >> CANbus >> digital isolator + microcontroller + LCD
since my application is developed on a CAN network (since this type of port is suitable for any environment and allows addressing). Using buffer and ser / des does not convince me, because I do not know exactly how to make a realistic test to measure the noise level, nor how to theoretically estimate it (if there are articles about it on ti.com, I would very much like to read them); moreover it would lead to complicate the Main board, occupy more PCB surface, ...
In your opinion, is this the best alternative? or the only feasible solution?

the article you posted is really interesting, it enlightened me about aspects that I considered "automatic" and gave me new questions:
-in what situations is the Parallel Line cable still used today? (I have a 3d printer at home, with an arduino processor that manages an LCD with Parallel Line of just under 1 m)
- you told me that not knowing the noise level, it is not possible to recommend an appropriate buffer. Going under 20cm of cable and redesigning my application, would I encounter any noise issues? (The LCD screen has a very low resolution 128 x 64 Pixels. I don't care if some pixels are not lit in the correct way as I think I refresh the screen 4 or 5 times per second or if an "event" is activated for the pressing a key, manageable by an interrupt)

Regards,

Danilo