Alternate Ethernet PHY Pins

[simonedwards]

Hi,

I’m designing a custom board, targetting the OSD3358-512M-BSM part and would like access to the DCAN0 and DCAN1 peripherals (among others).  Looking at the pinmux to do this, I see that DCAN0_TX_MUX0 uses the same balls as MII1_TXD3.  The other mux for DCAN0 is the same ball as UART0 which I really need for debugging!  So, my question is, what alternative pins are there for MII interface to my Ethernet PHY?  What do I have to do within Uboot and/or the Kernel to get this to work?

Thanks,

Simon

[Erik Welsh]

If you look at the TI Pinmux Tool (https://dev.ti.com/pinmux/app.html), you can see that the IO Sets for

DCAN0 (TX/RX):

• gmii1_txd3/gmii1_txd2
• uart0_rxd/uart0_txd
• uart1_ctsn/uart1_rtsn

DCAN1 (TX/RX):

• uart0_ctsn/uart0_rtsn
• uart1_rxd/uart1_txd
• mmc0_clk/mmc0_cmd

From this, you can see that you can get both DCAN peripherals by using all of UART1, all of UART0, or some of the MII1 and MMC0 pins.  Given you need UART0 for the Linux console, then you can use UART1.  If you still need to use the MII1 pins for the DCAN, then you can use MII2 peripheral, which uses the GPMC_A0 – GPMC_A11 pins, for Ethernet.

In order to make everything work under Linux, you will need to modify the device tree to configure the correct peripherals.  Also, be careful about the IO Sets for each peripheral.  Even though a peripheral may be muxed to many pins, not all combinations of pins are legal.  You can use the TI Pinmux tool to understand the IO Sets associated with each peripheral.  Then for the OSD335x-SM, you will need to map the pin numbers in the Pinmux tool using the pin mapping guide: https://octavosystems.com/app_notes/osd335x-family-pin-assignments/

[simonedwards]

Hey Erik,

Thanks for your response and sorry for not acknowledging it sooner.  I’ve used the pinmux tool from TI and have chosen to use the MII2 pins for Ethernet.  I then used the Excel spreadsheets to cross check and choose the OSD335x-SM balls accordingly.

Do you offer a service to check through ball allocations and schematics?

Thanks,

Simon

[Greg Sheridan]

Hey Simon,

I am glad you were able to make progress.

Please reach out to us via our contact us page to talk with one of our Business Development Managers about how we might be able to help you further.

 

Thanks,

Greg

[Author]

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