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header and USB for BBB

Nick King
Expert 1280 points

Dear TI

i can see from the data sheet max voltage for gpio is -0.5 to 0.3V 

Questions:

  • on the 40 pin header P9 of the BBB i can see VDD_5V,SYS_5V,VDD_3V3B are they input or output or bidirectional voltage supply?
  • and i don't understand why the MMC1_DAT0, MMC1_DAT1, MMC1_DAT2, MMC1_DAT3, MMC1_DAT4, MMC1_DAT5, MMC1_DAT6,MMC1_DAT7, MMC1_CMD and MMC1_CLK are connected to the 40 pin header is it to connect an external memory (MMC1) device to the BBB or to allow external processor to access the MMC1(memory device) of the BBB.
  • USB1_OCn is connected to the T16 of the sitara processor since my prototype board needs 2 USB's hence i have connected the USB2_OCn on pin V17 of the processor can you please let me know the changes to be done from the software point of view(device tree) so that the USB core knows that USB2_OCn is connected to V17 pin of the processor. 

Regards

  • 0
    TI__Guru**** 393215 points

    Hi,

    Nick King said:
    i can see from the data sheet max voltage for gpio is -0.5 to 0.3V 

    This is no correct. Max. voltage is from -0.5V to VDDSHVx+0.3V. this would be from -0.5V to +0.3V if the corresponding VDDSHVx voltage is off.

    Nick King said:
    on the 40 pin header P9 of the BBB i can see VDD_5V,SYS_5V,VDD_3V3B are they input or output or bidirectional voltage supply?

    The BBB should never be powered through the expansion headers. 

    Nick King said:
    and i don't understand why the MMC1_DAT0, MMC1_DAT1, MMC1_DAT2, MMC1_DAT3, MMC1_DAT4, MMC1_DAT5, MMC1_DAT6,MMC1_DAT7, MMC1_CMD and MMC1_CLK are connected to the 40 pin header is it to connect an external memory (MMC1) device to the BBB or to allow external processor to access the MMC1(memory device) of the BBB.

    If you put the eMMC in reset you can use these signals on the expansion header. They are not intended to access the eMMC from external sources.

    Nick King said:
    USB1_OCn is connected to the T16 of the sitara processor since my prototype board needs 2 USB's hence i have connected the USB2_OCn on pin V17 of the processor can you please let me know the changes to be done from the software point of view(device tree) so that the USB core knows that USB2_OCn is connected to V17 pin of the processor. 

    Which Linux SDK are you using?

  • 0 in reply to Biser Gatchev-XID
    Expert 1280 points

    thanks biser i am using Linux SDK 08.00.00.00

    1) additionally i am using just one user led more can you please let me know the code so that i can optimize.
    2) i have removed the HDMI phy chipset in my own version of prototype hardware i can see from schematics I2C and SPI and connected to the phy chipset hence need i need to disable that piece of code as well.
    3) USB2_OCn on pin V17 of sitara processor.
    4) so basically VDD_5V,SYS_5V,VDD_3V3B ,MMC1_DAT0, MMC1_DAT1, MMC1_DAT2, MMC1_DAT3, MMC1_DAT4, MMC1_DAT5, MMC1_DAT6,MMC1_DAT7, MMC1_CMD and MMC1_CLK are for testing/measuring am i correct ?

    Regards
    Nick

  • 0 in reply to Nick King
    TI__Guru**** 393215 points
    1. I cannot help on software questions. I will ask the software team to look.
    2. Same as above.
    3. I'm pretty sure overcurrent isn't implemented in software, as these signals are not connected on the AM335X GP EVM.
    4. These are expansion headers. There are different Beaglebone Capes that connect to these headers.
  • 0 in reply to Nick King
    TI__Guru**** 161600 points
    Hi Nick,

    "1) additionally i am using just one user led more can you please let me know the code so that i can optimize."
    You can just add an additional ledX node in your dts file along with the correct pinmux settings. Take a reference from the existing LED nodes.

    "2) i have removed the HDMI phy chipset in my own version of prototype hardware i can see from schematics I2C and SPI and connected to the phy chipset hence need i need to disable that piece of code as well."

    The spi you refer to is actually muxed as MCASP, so yes, if you remove the HDMI node, it would be good to remove the mcasp node as well. Refer to sound, hdmi, clk__mcasp0_fixed, hdmi_audio & mcasp0 dts nodes & mcasp0_pins pinmux node.
    As for the i2c, you can see that it is used only in hdmi node, so when you comment/remove the hdmi node will take care of the i2c0 part of the dts as well.

    Hope this helps.

    Best Regards,
    Yordan
  • 0 in reply to Biser Gatchev-XID
    Expert 1280 points

    thanks biser

    but if i see the USB1_OCn  it is connected to the  T16 pin of sitara processor obviously the processor must be doing something about it.

  • 0 in reply to Nick King
    TI__Guru**** 393215 points
    If it's not configured in the device tree it's surely not used.
  • 0 in reply to Yordan Kovachev
    Expert 1280 points
    thanks yordan

    ok let me explain again out of the 4 user led's i am using just one so i removed 3 leds in my own version of hardware hence i am looking for code changes to disable code for the remaining 3 leds in device tree and in source code as well.

    also USB1_OCn it is connected to the T16 pin of sitara processor obviously the processor must be doing something about it. may i know either device tree changes or the source code changes i need to add another USB2_OCn since i have 2 USB host.

    you said refer to sound, hdmi, clk__mcasp0_fixed, hdmi_audio & mcasp0 dts nodes & mcasp0_pins pinmux node is this a path or what?
  • 0 in reply to Biser Gatchev-XID
    Expert 1280 points
    ok thanks let me see in device tree
  • 0 in reply to Nick King
    TI__Guru 63125 points
    The USB PHY in AM335x monitors the voltage on VBUS and sends an internal signal to the controller to indicate an over-current condition. So the over-current output from the VBUS power switch is not necessary.

    Regards,
    Paul