Magic shield plates helps naked A20-OLinuXino-LIME2 board to pass CE EMC requirements.


A20-OLinuXino-LIME and A20-OLinuXino-LIME2 are choice for many industrial applications, when the board is inside metal box like BOX-LIME:


it has no problems with shielding the radio emissions, but when just board is used as component, our customers has to shield it by their own in their designs. We had number of request to do official CE EMC certifications for A20-OLinuXino-LIME2 as this would make their life easier, and we decided to do this after we already get some experience with the certification of USB-ISO and ESP32-POE-ISO.

Initially the naked board failed on EMC measurements as seen here from the test results.


The major problem is the Gigabit Ethernet PHY. You can see spikes at 125 Mhz, 325Mhz etc. Disabling the PHY removes all noise and everything is in safe levels. So we knew who is ther trouble maker.

The major noise emitter are the Transmit and Receive clock lines. We put 33 ohm resistors in series R119 and R123 in A20-OLinuXino-LIME2 schematic , but obviously this was not enough. To further fade the line harmonics we replaced the resistors with 0402 Ferite Beads with 600 ohm impedance at 100 Mhz. This lowered the emissions, but still not well enough to be at safe levels.

So we had to make small Faraday cage on top:


and bottom of the board:


this effectively removed all noises and the A20-OLinuXino-LIME2 pass CE requirements:





We are preparing now to implement the Ferite Beads on PHY Tx and Rx lines in all our other boards production assembly, and will offer the shield plates as kit they are good for A20-OLinuXino-LIME and A20-OLinuXino-LIME2 and we will prepare same for A20-OLinuXino-MICRO and A64-OLinuXino.


Lime2-SD add on board for second SD card on A20-OLinuXino-LIME2


Lime2-SD is small add on board which snaps on GPIO-1 connector and add second SD card to A20-OLinuxino-LIME2. It doesn’t interference with other parts on the board and do not increase the height.


Why we do this? Because this is an easy way to increase storage for Pioneer-FreedomBox-HSK . What we are preparing to offer soon is upgraded version of the Home Server Kit with 256GB storage made with 2 “disks” x 128GB micro SD cards. For these who already have Pioneer-FreedomBox-HSK they still can upgrade by ordering Lime2-SD .

Note that support in FreedomBox for Lime2-SD is not add, but you can try Lime2-SD with the current Armbian image for LIME2. To enable the Lime2-SD support you also have to add this dts overlay .


A20-OLinuXino-LIME2 now with PCB revision G


A20-OLinuXino-LIME2 now is assembling on same PCB Revision G as A20-OLinuXino-LIME2-eMMC.

What are the improvement:

  • Ethernet PHY is changed to RTL8211E replacing the obsolete RTL8211CL no need for kernel patches;
  • we drop the odd shape which was necessary to fit LIME2 in the plastic box as we now have range of metal boxes;
  • the four mount holes now have grounding for better contact with chassis;

Meantime we silently work on further improvement for next revision (to be released March 2017):

  • adding SPI boot Flash;
  • replacing RTL8211E to industrial grade PHY, so the board can be produced completely in -40+85C operating temperature;


Alternative Linux images for LIME and LIME2


Igor Pecovnik has created optimized Debian image for Cubie board named Cubian, he asked for sample board and we sent him LIME2 so few days after he received the board he generated optimized Debian image for LIME2, you can see the instructions and images on his blog:


Remy van Elst did minimal Debian 7 for A10-OLinuxino-LIME

A20-OLinuXino-LIME2 review and updates


Sorry for blogging so late for A20-OLinuXino-LIME2 but last two month every week I had to travel somewhere.

This is also the reason for the two last weeks without Weekend Programming Challenge and Friday Free Board Quiz.

I promise these will be resumed next week after Open Fest 🙂

A20-OLinuXino-LIME2 is product of the continual improvement of our OSHW OLinuXino boards based on your feedback, tips and suggestions.

The major differences to A20-OLinuXino-LIME are:

1. Much better routing of DDR3 memory. We increased the number of layers to 8 vs the 6 layers in LIME, we put the DDR3 memory closer to the A20, we layout the tracks shorter, as result now LIME2 runs with DDR3 on 532Mhz on LIME there were problems to run DDR3 at more than 400Mhz.

2. Double the memory, LIME2 now is with 1GB RAM and we expect 8Gbit DDR3 memories to experiment on having LIME2+ with 2GB RAM (shhhhht do not tell anyone and do not ask when it will be available as we also don’t know if these experiments will be successful).

3. Faster Ethernet, now we use A20 GMAC instead of EMAC so LIME2 have Gigabit Ethernet.

4. GPIOs 0.05″ connectors now made right. When we designed LIME we first though to use female connectors instead of male, but when we finished the design we realized that this time we will break the order we made all “mother boards” to have male connectors (to may connect to ribbon cables) and the shields/modules/capes to have female connectors. In the last moment we decided to make LIME with male connectors and we had the dilemma – to go again to re-routing and prototyping or just to assembly the female connectors with male, we wanted to release LIME earlier so we went with the latter without realizing that this way when cable is attached the cable numbering will be mirrored!

Once we made this mistake we continued it with A10-OLinuXino-LIME-UEXT as otherwise we couldn’t have functional extension board.

Then we had internal discussion if we have to make these GPIOs right, the problem was that there were already many thousands LIMEs sold so what to tell to our customers who already bought LIME and made shields for it? So we left it “as is”.

In LIME2 we decided to make it right and LIME2 is with connectors which have no mirror, but this make them incompatible with LIME 😦  What we will do now is to make new version of LIME with correct GPIOs, but we will keep the production of the old LIME too, just have to figure out how to name the new board to not add more confusion to our customers.

So to conclude about the GPIOs:

LIME and LIME2 connectors are with different layouts (mirror). This means you can’t use A10-OLinuXino-LIME-UEXT on A20-OLinuXino-LIME2. We have A20-OLinuXino-LIME2-UEXT which is in production and will be ready around 10th of November in Stock.

Also new version of our A13-LCD4.3 A13-LCD7 and A13-LCD10 is developing which have standard 40 pin LCD connector to attach to A13-OLinuXino and A20-OLinuXino-MICRO + two small connectors for direct connection to LIME and to LIME2. I hope this is not confusing for you too :)))

Here is picture on the new LCDs:


as you can see you can connect directly now any of our boards including LIME and LIME2 without need to go through adapter board.

I’m sorry for all these confusions but we decided to make thing right and move forward than to keep the GPIO error forever (Arduino for this reason keeps the shield connectors off 0.1″ step, they made initial mistake but decided to not correct it).

Now we will have the inconvenience to keep LIME (mirrored GPIOs), LIME2 (correct GPIOs) and NEW-LIME(correct GPIOs) but this is our mistake and we want to fix it.

EDIT: Something important! Debian and Android images for LIME and LIME2 are different because of the memory and Gigabit ethernet, so if you have LIME download the images for LIME if you have LIME2 download the images for LIME2!!!