We startd our OLinuXino with RT5350F back in July right before our Summer vacation.
As soon as I blogged about it we got tons of useful tips and advices on the blog and by e-mails, like info about RT5350F frequency tunning, Antenna design, Overheating internals, which was not obvious from the skinny info on the web.
We decided to build two prototypes one with integrated and one with discrete baluns and on the picture above you can see the version with balun on left and discrete components on right side. Here is how the boards look on back side:
Our first intention was to make this board with 64MB of RAM and 8MB of Flash, but after reading more carefully the datasheet we found that this will require two RAM memory banks and two chips, which would increase the size of the board, so we decided to keep the size and make only 32MB RAM, but to increase the Serial Flash to 16MB.
The prototypes start working from the very first time, which makes me to worry about what we did wrong🙂
The schematics and CAD files are on GitHub. Note these are preliminary and we have to update them with the latest components exchanges like SPI memory now is W25Q128FVSSIG and RAM is W9825G6JH-6.
Although we got tip for the tendency RT5350F to overheat (it uses internal LDO for 1.2V which dissipates enormous amount of heat and can cause the chip to desolder from the high temperature, we are non-believers and wanted to try ourself… well the result is that RT5350F really overheats🙂 as this 1.2V could be feed from outside too, this will be solved in the next revision and we will put small external DCDC to release RT5350F from this heat source inside the chip.
This is our test setup we made small carrier board with 5 Ethernet ports and USB host to may test the board functionality, do you see the big heatsink🙂 :
the cable on the left side is JTAG for initial uboot programming to the SPI Flash, the small board on the right side is the USB-Serial for the console.
The OpenWRT is running fine, so after all tests are done next week we will experiment to lower the heating and make new prototypes.
What we still didn’t decided yet is what EVB to make for this board?
Initial though is:
- x1 or 2 Ethernet ports
- x1 USB host
- x2 RELAYs
- few GPIOs with optical isolation
- UEXT with UART/SPI/I2C for connecting UEXT modules
- small 4 digits 7-segment display
- all this put in nice compact DIN enclosure
it will be easy to put on DIN rail and to measure things and connect to Internet:
Definitely with these problems of the overheating the board will have no problem to run on negative temperatures, just the problem will be if the ambient temperature rise above 40-50C🙂 but let’s see what will happen with external DCDC in the next revision.
As always we are open to hear your suggestions🙂