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Altera_Forum
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15 years ago

Bemicro PWR_N signal and USB

Hi. I'm using a Bemicro development board for learning Verilog and VHDL and I want to make an expansion board. I have read in the manual that an expansion board can use the PWR_N signal to enable the on-board regulator and supply 5VCC to Bemicro. Also I have read if solder bridge B600 is modified USB can't be used or the board can be damaged, but it doesn't say anything about use USB with PWR_N signal on. I think USB can't be used too, but I'm not sure.

Can I use USB connection with PWR_N and external supply voltage?

Thanks in advance.

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    The PWR_N signal is connected to a diode or circuit (V700) and doesn't short other signals. But the external +5V terminal is directly connected to VUSB and shouldn't be driven when USB is plugged in.

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Hi. Thanks for your help, FvM. I'll try to cut-off the VBUS line from the USB connector, connect the external power supply and drive PWR_N signal low. So I think I could load my configurations using external power.

    Thanks.
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    If I understand right, PWR_N is also holding the FTDI device in reset, so USB won't work with PWR_N activated. Why don't you simply add an EPCS device to store the configuration permanently?

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Hi. I soldered a EPCS16 and works fine, but I'd like not to need to remove the bemicro from the host board I'm building every time I want to test a new configuration, so I think a good solution would be to use a switch to control PWR_N and +5V signals and detach it when I want to plug the bemicro to an USB host.