SPI interface on J1 connector

  • Hello,

    I would like to clarify the question of SPI CS/MOSI swap on J1 connector.

    If I understand chapter 4.5 of document PicoCOMA9X_Hardware_en.pdf well, in older hw J1-27 was SPI_CS and J1-29 was SPI_MOSI.

    In newer hw J1-27 should be SPI_MOSI and J1-29 SPI_CS.

    I tested those pins on module Rev. 1.20 (assuming it is a newer hw) but if I set pins via /sys/class/gpio interface then changes of gpio47 can be measured on J1-29 and changes of gpio48 on J1-27.

    What is the problem? Are these J1 pins wired differently when configured as gpio or spi? Is our module (1AA4AC) really the one with fixed swap of pins?

    Thank you,


  • Yes, SPI_MOSI was on J1-29 and SPI_CS was on J1-27 on PicoCOMA9X, but it should have been SPI_MOSI on J1-27 and SPI_CS on J1-29 like on all other PicoCOM modules. So this was wrong.

    Now Board Revision 1.20 has an optional fix for this. Here we can configure both variants. We can set solder jumpers to the old (wrong) setting and also to the correct setting. However as most customers are already in the field with their products and have arranged with the swapped setting, we assume that shipping modules with the correct setting now might cause some confusion with them. This is why we actually continue to ship the wrong configuration, even with Board Rev 1.20.

    If you want to have the "correct" configuration, please contact our sales department to check if this is possible.

    Otherwise I simply suggest to also add solder jumpers to your baseboard, so that you can swap pins 27 and 29, too. For PicoCOMA9X, you use the swapped configuration. And if you ever want to use a different PicoCOM module with the correct pinout in the future, then you can use the unswapped configuration there.

    Your F&S Support Team

    F&S Elektronik Systeme GmbH
    As this is an international forum, please try to post in English.
    Da dies ein internationales Forum ist, bitten wir darum, Beiträge möglichst in Englisch zu verfassen.

  • As we need to replace PicoCOMA5 with newer PicoCOMA9X in the existing hw, we cannot add jumpers to our board and we need to have a standard PicoCOM interface.

    We only have a few samples of PicoCOMA9X, but later when we will order more we will try to order the ones with the correct jumpers configuration.

    But now I need to change it myself - problem is that I cannot find the physical location of these jumpers in the documentation. Can you provide me with some picture or other information with their position?

    Thank you,