Apalis IMX6 Access to MDIO SMI Pins

Is it possible to access IMX6 MDC through the Apalis edge connector?

In the Apalis IMX6, I suspect the onboard KSZ9031 phy is connected to the primary SMI pins (pad names ENET_MDC and ENET_MDIO), which are unfortunately not brought out to the Apalis edge connector.

ENET_MDIO is also available on pin 140 (pad KEY_COL1) so that is ok.
ENET_MDC alt is on pad KEY_COL2 which looks like it is used for touch interrupt and does not go to the edge connector.

Is there any other way to access ENET_MDC on Apalis?


Unfortunately, the ENET_MDC interface is not available on pin that is located on the edge connector. I do not understand why you need to have the MDIO/MDC interface externally accessible. The i.MX 6 features only one Ethernet MAC. Even tough, the ENET_MDIO is available as alternate funciton on pin 140, it cannot be used as long as the on module Ethernet PHY is in use. The MDIO function cannot be used simultaneously on two SoC pins.

If you need to have a secondary Ethernet interface on an Apalis iMX6, you have several options:

  • Place a PCIe Ethernet Controller on the carrier board. In our Apalis Carrier Board Design Guide on page 18, you find an example schematic for the Intel i210 or i211 controller. Download the document here.
  • Place an Ethernet switch on the carrier board. It is possible to use capacitive coupling between the module and the switch instead of a normally used magnetics in order to save space and cost
  • For 100Mbit/s Ethernet, a USB Ethernet controller could also be a solution.
  • The Apalis iMX8 will be the first module in the Apalis form factor which features a second Ethernet MAC. This module has a second RGMII/RMII (including MDIO/MDC) interface on the module edge connector. This allows having a secondary Ethernet PHY on the carrier board.

Thanks. The use case for needing MDIO/MDC on the carrier board is in the case of your 2nd bullet point… if you make a carrier board with an enet switch and phys to the other switch ports, you would need the management interface to configure the extra phys or else select a part that is configurable via i2c or spi.

Thank yo for clarification. The designs with an Ethernet switch on the carrier board I have seen so far did not use a MDIO/MDC for management. Besides the modules which feature a secondary Ethernet MAC and therefore an independent MDIO/MDC interface, we have the Colibri iMX6ULL and the upcoming Colibri iMX8X which share the on-module MDIO/MDC interface with the carrier board. Unfortunately, the Apalis iMX6 has really no option for having an MDIO/MDC interface on the module edge connector.