Leen09
Posts: 1
Joined: Tue Nov 19, 2019 3:06 pm

1.8V GPIOs on Pi 4?

Tue Nov 19, 2019 3:13 pm

For a project I need to interface with an external device which has a 1.8V control interface, using Mipi RFFE (3 wire interface). I need to write to the external device and read from it as well, thus the pins need to be bidirectional. I understood that the GPIOs on the BCM2835 support 1.8V, and that the Compute Module has a jumper to select 1.8V. How can I achieve a 1.8V interface on the Pi 4?

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Raspberry Pi Engineer & Forum Moderator
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Re: 1.8V GPIOs on Pi 4?

Tue Nov 19, 2019 4:00 pm

Leen09 wrote:
Tue Nov 19, 2019 3:13 pm
For a project I need to interface with an external device which has a 1.8V control interface, using Mipi RFFE (3 wire interface). I need to write to the external device and read from it as well, thus the pins need to be bidirectional. I understood that the GPIOs on the BCM2835 support 1.8V, and that the Compute Module has a jumper to select 1.8V. How can I achieve a 1.8V interface on the Pi 4?
You can't.
On a CM your carrier board provides the GPIO reference voltages via GPIO0-27_VREF and GPIO28-45_VREF, and hence you can configure each bank for either 1.8V or 3.3V operation.
On a Pi4 those connections are made within the board, with both connected to 3.3V. You'll need to use external logic level conversion.
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