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Altera_Forum's avatar
Altera_Forum
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7 years ago

Changing single GPIO Pin output voltage

Hi,

I am trying to do connect a video camera (OV7670, from Omnivision) on altera DE2 (EP2C35F672CN - Cyclone II). I got stuck on one question: I would like to avoid using external circuitry to do voltage dividers, since one of the camera pins must be supplied with a lower voltage. Is it possible to change the output voltage from a single pin from the GPIO for that? In my case, I would like to use something next to 1.65V. I tried to change the pin for 1.8V using the pin planner, but it seems that it is not working. I got the following error message:

"Error (169026): Pin GPIO_0[21] is incompatible with I/O bank 5. It uses I/O standard 1.8 V, which has VCCIO requirement of 1.8V. That requirement is incompatible with bank's VCCIO setting or other output or bidirectional pins in the bank using VCCIO 3.3V."

Does anybody have any suggestions on how can I do this?

Thanks

Marcio

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    7 years ago

    Hi,

    This error occurs when a bank is using vccio=3.3V and we try to use 1.8 V for one/ more pins in the same bank in your design.

    1. We can't change voltage for a single pin in the Bank, You can change the VCCIO for the entire bank.

    2. External circuitry is like a level shifter are required.

    To change the voltage of an I/O bank using the Pin Planner refer below link.

    https://www.altera.com/support/support-resources/knowledge-base/solutions/rd08172009_2.html

    Best Regards,

    Anand Raj Shankar

    (This message was posted on behalf of Intel Corporation)
  • Altera_Forum's avatar
    Altera_Forum
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    7 years ago

    Thank you for the information. I tried to change the Bank voltage for 1.8V in GPIO_1 bank for using just only one pin from it and the rest from GPIO_0. I measured the voltage from the pin and it still has 3.3V . Is there something that I did wrong? Or when you said that external circuitry is required, you meant that changing the IO bank on Quartus II will not reduce the output voltage ?

    Regards,

    Marcio

    --- Quote Start ---

    Hi,

    This error occurs when a bank is using vccio=3.3V and we try to use 1.8 V for one/ more pins in the same bank in your design.

    1. We can't change voltage for a single pin in the Bank, You can change the VCCIO for the entire bank.

    2. External circuitry is like a level shifter are required.

    To change the voltage of an I/O bank using the Pin Planner refer below link.

    https://www.altera.com/support/support-resources/knowledge-base/solutions/rd08172009_2.html

    Best Regards,

    Anand Raj Shankar

    (This message was posted on behalf of Intel Corporation)

    --- Quote End ---

  • Altera_Forum's avatar
    Altera_Forum
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    7 years ago

    Did you change vccio supplied to that bank? Try measuring the supply rail for that bank.

  • Altera_Forum's avatar
    Altera_Forum
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    7 years ago

    I suspect a misunderstanding. Bank voltage is a hardware thing, the pin planner setting has to reflect the actual VCCIOx voltage but can't alter it.

  • Altera_Forum's avatar
    Altera_Forum
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    7 years ago

    You need to check the VCCio voltage for that Bank in question. If it is set to 3.3V then the pins in the bank will be set to 3.3V only. On the other hand if you have like a jumper to change the VCCio on the board between 3.3V and 1.8V then you can change the jumper and set the voltage to 1.8V. Be warned though, changing the Bank VccIO voltage will affect all pins in that Bank. You cannot change only one pin or selected pins to a different voltage in a Bank. Check if you have any other unused GPIO bank and what voltage VCCio is driving it. If so, then change the Voltage standard for that Bank and try.