Is this i.MX233 design OK - Page 1
Forum section: electronics / projects

author: daveshah
author_rank: Unknown
timestamp: February 19, 2015, 08:18:08 am
content: HiI'm only 17 and I'm relatively new to the world of high speed digital design, so I would be most grateful if somebody with more experience could check over my schematics and PCB designs for an i.MX233 based handheld games console. I have tried posting this to the Freescale forum already but no one has been able to help me yet, so I'm wondering if someone here has experience with these devices.The design is split across three PCBs - a 4-layer board with the processor, RAM and LCD; and two 2-layer boards (both the same design and schematic) with the buttons and audio/video jacks. This is to keep the cost of the project down by minimising the size of the expensive 4 layer board. Most of the core design is based on the official reference design and Olimex's Olinuxino designs. A slight deviation from most designs is that I am using 3 AAs, rather than a Li-ion cell for the batteries, and therefore I have an LDO to reduce the voltage to levels which will not damage the processor. The LCD is running in serial RGB mode, which I believe is supported by the processor, it would be interesting to know whether anyone has got this to work before.I have attached PDF schematics and PCB gerbers for both boards as well as the original KiCad source files (these were made with a recent development version of KiCad, if you want to view them you might need the build fromhttp://kicad.nosoftware.cz/.Thanks

author: Ice-Tea
author_rank: Super Contributor
timestamp: February 19, 2015, 08:29:56 am
content: Without going into detail: be carefull when assuming putting your buttons on a 2L board will be cheaper in the end. PCBs (at least in volume) are not expensive, and even though a 4L board will be some 50% more expensive, you have to weigh this against the connector cost, additional labor, setup and maintenance costs. Might not be worth the trouble.

author: daveshah
author_rank: Unknown
timestamp: February 19, 2015, 08:42:13 am
content: I'm only intending to make a few of these for now, and as I'm planning to buy the boards from Elecrow there is a big jump between 5x10cm boards and larger sizes.

author: 8086
author_rank: Super Contributor
timestamp: September 12, 2016, 04:16:27 am
content: Did this design work out for you? I am having issues with bringing up a custom imx233 board so it would be interesting to see if you succeeded.

author: homebrew
author_rank: Frequent Contributor
timestamp: September 12, 2016, 08:35:30 am
content: Hi, great effort for a 17 yo!Schematic looks nice from a first glance. Hope you had some reference design ...Regarding the board, I would really look into the DDR section again. DDR is not trivial and as far as I can see, you have neither routed differential pairs, nor is there any length matching. On the other hand everything is reasonably close and the wires are short ...Look here, as a reference:http://www.samsung.com/global/business/semiconductor/file/product/Mobile_DRAM_app_note_for_PCB_Design_guide_rev0-1.pdfI would be extra careful here, because you probably don't have any chance of debugging ...

author: daveshah
author_rank: Unknown
timestamp: September 12, 2016, 08:50:09 am
content: The design was based of Freescale's own reference design and the Olinuxino designs.It's been a over a year now since I last touched this project; but from memory the design did change slightly since the ones I posted, mostly around the LCD (switched to an "intelligent" parallel panel). I'll try and dig out the final files at some point.I did get it to work; although the type of DDR memory IC I used (AS4C32M16) required me to enable DDR "low power mode" (HW_DRAM_CTL05_EN_LOWPOWER_MODE ) in the bootlet (can't remember the exact setting) to get it to work reliably. Without this enabled it worked but not reliably which was fustrating to debug as it generally crashed as it was loading Linux - I seem to remember replacing the microSD card socket at least once as it felt like a mechanical issue. I also tried underclocking the DDR to 64MHz but I don't think that was necessary once the low power mode was enabled.

author: daveshah
author_rank: Unknown
timestamp: September 12, 2016, 08:58:08 am
content: What I believe to be the final design files in KiCAD format are attached along with a photo of the PCB booting; unfortunately this project is from before I used proper version control so I can't guarantee I didn't subsequently break them in some way or another.