iMX RT1020 RMII with external clock

[bensonyoung]

Hello,

I am using RT1020 to connect to a switch via RMII interface.

The reference clock is provided by the switch.

and I am using the SDK sample code

lwip_tcpecho_freertos

Do I only need to make modification to change the ENET_TXCLK direction to input?

IOMUXC_EnableMode(IOMUXC_GPR, kIOMUXC_GPR_ENET1TxClkOutputDir, false);

i have modified the PHY initialization flow so that the lwip stack appears to be running, and the switch's PHYs can establish link with external connection. But somehow the iMX RT1020's MAC cannot 'see' any packets.

I am sending arp requests.. and there is nothing at the MAC layer. I am suspecting I am missing something.

your assistance is greatly appreciated.

[victorjimenez]

Hello Benson, 

In RMII mode ENET_REF_CLK signal is the reference clock for receive, transmit, and the control interface. According to Table 36-2 of the reference manual, this pin by default is set as an input. 

Have a great day,
Victor

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