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I'm going to design an Arm Cortex-A53 based core-board and this core-board will be used in many different projects with different applications. Sometime it will be used in a generic device to just run simple Android applications, sometime in an embedded system for collecting data from different devices USB, SPI, UART, And etc. So in each application i just need some specific peripherals of the SoC. For example when it is used to just run android and simple apps, i just need the display interface to connect to an LCD and a microSD card (No sound, WiFi, Ethernet, HDMI and ... is needed). in another application i will use the board to just connect to HDMI and connect to internet with Ethernet.

I'm checking for feasibility of designing my core-board in a modular way. My idea is to put the main parts that are fixed and nescessary in every systems(processor,DDR Rams, Flash Memory, main power management, Programming Port) on the core-board and then make a collection of connectors around the board. one connector for every video pins of the processor containing LCD, HDMI and Camera and another one for communication interfaces like SPI, UART, USB, Ethernet and audio and other things like this. after that whenever I need this board to connect different devices with USB and UART, I design a separate board containing USB and Uart circuit and connectors and connect this board to the core-board with a appropriate connector. In this way I every other extra connectors are omitted from my design. My goal is reducing the space and cost and improve security.

My questions are:

  • If I do my design in this way, is there any consideration that i should take care of with highspeed routes like usb, hdmi and ... . I mean if for example the hdmi pins are connected to a connector then this connector is connected to the same connector on the other board with a cable, is there any Signal Integrity problem that i should take care of?

  • if designing in this way is feasible, which kind of connector is the best choice for connecting two board to each other? are FFC and FPC connectors good choices?

  • in general, what is the criterion for choosing a connector specially in high-speed designs?)

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Certainly is feasible - usually sold as "computer-on-module", like the Raspberry Pi compute module. In that case the core board interfaces to a mainboard over a SODIMM connector.

You do have to take care of signal integrity over daughterboard connectors. What you may find is that having lots of connectors isn't cost-effective; good connectors are surprisingly expensive.

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  • \$\begingroup\$ If application allows, there are relatively cheap connectors from mobile market. \$\endgroup\$ – Gregory Kornblum Apr 17 '17 at 10:25
  • \$\begingroup\$ @GregoryKornblum .. such as? \$\endgroup\$ – pjc50 Apr 17 '17 at 10:31
  • \$\begingroup\$ such as molex slimstack. Don't remember the names, but fci and herose have some too. Samtec are champions, but expensive really. Although for prototypes and small volumes, or for high end equipment- my first choice. \$\endgroup\$ – Gregory Kornblum Apr 17 '17 at 10:36
  • \$\begingroup\$ By the way, SODIMM is also quite cheap. Again, not good for industrial applications, but maybe good for this one. \$\endgroup\$ – Gregory Kornblum Apr 17 '17 at 10:38
  • \$\begingroup\$ thanks for your answer. in some applications the height of the board is important and with SODIMM connectors the board's height will be more than double. how about FFC connectors? are they appropriate choice for this application? \$\endgroup\$ – Milad Apr 17 '17 at 10:38

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