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Johnnyjax , 06-03-2020, 10:33 AM

I just finished the advanced PCB layout course and i decided to challenge myself by designing my own imx6 board but i have some questions. The first challenge i faced was trying to understand the schematics of the imx6rex module and baseboard, which is really tough because you only focused on the PCB layout. Are there any ideas you can give me on how i can fully understand the schematic layout so that ill be able to design my own board because i couldnt find any ideas from the datasheet. I decided to make my board a 6 layer board with through hole vias only but i also removed the hdmi, lvds, ethernet, pcie and so many other peripherals and left only one USB OTG, spi flash, UART header, DDR3, CPU, power supplies and 1 MMC card circuit all on the same board. Will a board with just these peripherals be useful and will it still be able to run linux and is a board like this route-able on a 10cm by 10cm board since i've removed a lot of the complex sections from it. I also need information on what to do after i manufacture a board like this because i dont know anything about operating systems or running linux on boards. Where can i get this information? Thanks.

chitransh92 , 06-05-2020, 02:20 AM

Hello.

There are different ways to do this as each one has their own way and all are right.
I would suggest you start of at Micro-controller and check its details at a high level, then you can move on to the peripherals as they allow you to connect to the external world and then memory ICs step by step.
MCU and Peripherals will cover of over 70-80% of the HW design part.

• "Useful" is always a subjective term.if you are thinking to commercialize it then it might not be useful, if you are thinking of learning it will be useful.
• It will still run linux but the peripheral that you are planning to keep will not need a sophisticated OS like Linux. You can use a smaller OS like RTOS etc..
• Also USB OTG, SPI, UART and MMC are not very resource hungry so re-visit at your selection of Peripherals and decide if you still need big memory and speeds like DDR3???
• For routing check the component area, if it is 40% of board size then you can route it easily, if it is 50-60% of board area then it will be HDI type but still routing it possible...Do not go beyond that or it will be crazy mess..

@robertferanec has one course on this "Learn the Essentials of creating uBoot, Linux and YOCTO" you can use that as a reference.
Or else there are other books and courses available online on the topic.

All this being said..
I would encourage your desire to design your own imx6 board. However be mindful as it not a task that you can achieve in a couple of months.
It takes a lot and really "a lot"
Generally companies have different verticals to deal with HW and FW of a design as both have greater depths and require different set of skills and expertise..

@robertferanec will be able to comment on how long it took him to design this version of imx6 end to end. 🙂


Thank you.

Johnnyjax , 06-05-2020, 02:53 AM

Thanks a lot for the suggestions. I've designed a lot of microcontroller based boards in the past for microchip, atmel and stm32 microcontrollers and done various projects with them but nothing high speed with them. I just finished taking the advanced pcb layout course and did practically all the exercises so I think I should be able to layout a board like the imx6 rex now which is why I'm giving myself this challange and like I mentioned before, the major issue I've been having is the schematic design. I've gone through the schematic of the imx6 rex module and baseboard so many times already, trying to understand why even some resistors and capacitors or chips are there, and although robert tried to explain some of the reasons some components are there, there are still so many that are unclear. I've gone through the hardware development guides for imx6 processors and it helped a bit but the datasheet didnt really help. Which is why I want to know if there are any other resources I need to check out to fully understand the schematic design so that I can be able to design my own boards which might be a lot different from that of the imx6rex. Also, are you sure the peripherals I'm planning to keep wont run linux? I've seen a video of robert where he booted linux from just the imx6rex module alone without the baseboard and he did that with just the USB and UART. He booted it through the serial port so I think I should be able to boot linux from the peripherals i selected but I'm not sure so I'm hoping he can shed some light on this. And thanks for the suggestion about taking the fedevel course on linux. I guess I'll have to take that once I'm done with producing the board. Also I'm only doing this as a personal project and it's not commercial. I'm still a university student and I just want to try to design my own high speed board since I just finished the course.

Johnnyjax , 06-05-2020, 03:00 AM

And I've watched the video robert posted on youtube on how long it took to design the imx6rex module and baseboard so I'm aware of how long itll take and how complex it is but I'm not going to grow if I dont practice designing boards like this on my own. And I also selected ddr3 and the other peripherals i did because I'm looking to design a board that can at least run linux. I might not be able to if theres no ddr3 or uart or usb there. Maybe robert can comment on the least peripherals needed to run linux through a serial port.

robertferanec , 06-06-2020, 03:05 AM

@Johnnyjax use OpenRex https://www.imx6rex.com/open-rex/ as your reference design and cut it down (it is only through hole VIAs board). That is exactly how many boards are designed - based on reference boards. Initially, it is not necessary to understand every component in schematic - you still can design boards, more you are working on projects more you will pick up the patterns. Some people will not maybe agree - but I always say, you can use formulas in math without understanding how they were created. Of course, use common sense.

When you are designing for OS, if possible, do not change too much, otherwise you will have a lot of problems with software. You can cut the reference design down, but do not move features between pins, unless you know what you are doing (and unless you know what you will need to change in software to support that change)

PS; Our Yocto/Linux/uBoot course https://academy.fedevel.com/courses/...inux-and-yocto is also based on OpenRex, that would help you to bring your board to life.

Good luck with your project

Johnnyjax , 06-06-2020, 03:38 AM

Thank you so much.