Communication interfaces between boards

[FreshmanNewbie]

I would like to know whether my below design is feasible.

I have a UART interface in one PCB - Board 1.

I have another PCB board that needs to be connected to a TFT touch display - Board 2. Planning to use this.

Board 3 - Need to develop a board that will give power to the 7-inch TFT.

My question is, can I use board to board connector, to connect the UART interface between board 1 and board 2? Or should I use wires/cables between them?

1. Just want to know whether my above design would be feasible. Or do I need to check for any precautions for the digital interface, That is UART? In the case of cables/wires any distance limitation?
2. LCD and TFT technology are compatible? I am confused on how the data transmission will happen between board 2 and board 3. When I looked in the TFT datasheet, it is mentioned that the host processor interface that will be supported is I2C. So, the board 2, will be host. Any idea on how it will happen?

 

[KlausST]

Hi,

draw a skech, that shows all that is important for a detailed question.

Klaus

 

[Aussie Susan]

The UART module used in most MCUs operates at the IO voltage of that MCU - often 3.3V or 5V. That sort of voltage swing is OK for most connections within the board up to several mega-BAUD. If you want to connect your boards #1 and #2 via wires, then you also need to consider the distance between the boards - several cm and you should have no problems but get to several meters and you will need to 1) slow the BAUD rate down (to compensate for the distortions that the wire will inject) 2) use a different hardware protocol such as RS232 or RS432 or 3) both 1) and #2.
If Board #3 is the power supply, you will need to define why it needs a data connection and exactly what that data connection does. I2C has the same sort of considerations as for the UART above. Looking at the data sheet for the (now obsolete) board you want to use for Board #2, it has UART, SPI and I2C interfaces so you should be OK.
BTW, your first message seems to imply that the board you link to will be the TFT display - the data sheet only mentions that it has a graphics controller and a graphics connector - the display itself is not part of that board.
You don't tell us what you are trying to achieve overall - but I suspect that you are making this way too complex. Also I suspect that this is an 'X-Y' problem (https://xyproblem.info/) so take a step back and tell us the probelm you are trying to solve n the first place.
Susan

 

[D.A.(Tony)Stewart]

I read that the LCD interface is 50 pin parallel. What is your budget? or are you constrained to stock items.

 

[KlausST]

Hi,

I´m in pedantic mode because I just want to avoid that newbies get told the same old mistakes.

RS232 is not a protocol.
And I guess with RS432 you rather meant RS422. It´s not a protocol, too.

While RS232 is meant for two partners only (peer to peer), RS422 is prepared for multiple partners, it may be used as a bus, but it needs extra control signals/wires.

RS232, RS422, RS485 ... are interface definitions. They define the physical interface, the wiring and the signal levels, maybe even connectors.

A protocol describes (part of) the meaning of the data. Packet sizes, error correction, timing...

Example:
when two persons speak with each other:
* Physical interface: air, electrical wires (good old telephone), RF (cellular phones) .... often multiple physical interfaces are combined.
* Protocol: language, the meaning of the words, how they are sparated, error handling

Klaus

 

[D.A.(Tony)Stewart]

Perhaps you may have heard about the concepts of OSI, Open Systems Information. The hardware you have selected has a lot of IO interfaces and you will rely on many examples in the libraries and interfaces that you must control to find out if it will do what you want. You may want to define what you want in information bandwidth and content at the top levels before you choose at the bottom physical levels before you discover any barriers on cost or performance.

Although one rarely designs using OSI thinking, it is useful to compartmentalize the functions of each layer because it may be applied to all types of communication between systems, machines, ICs and humans. Learning the attributes of each is your challenge to understand the choices you will make.

It is most helpful if you start from the top requirements of your project or your design and make a list of assumptions that are unlikely to change for all inputs and outputs for Bandwidth, Latency, content and physical constraints. If you start with a cheap motherboard because it has a lot of industrial I/O types, keep in mind it might be connected to obsolete expensive displays so define your requirements 1st and must-have peripheral interfaces for HMI (human machine interface) in the top layer.

BTW the board you mentioned is not recommended for new design and is no longer manufactured but replaced with a newer version that must use a higher resolution interface display, again with a parallel interface. But if this is what you are given, may be OK for educational purposes.