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Broadcom & voltage

Posted: Sat Jun 22, 2019 1:21 am
by rvanspaa
Hi,

Quote from the Broadcom peripherals manual (page 89):-

"There are 54 general-purpose I/O (GPIO) lines split into two banks. All GPIO pins have at
least two alternative functions within BCM. The alternate functions are usually peripheral IO
and a single peripheral may appear in each bank to allow flexibility on the choice of IO
voltage."

Does anyone know what they are referring to by "flexibility on the choice of IO voltage"?

Re: Broadcom & voltage

Posted: Sat Jun 22, 2019 11:23 am
by Gavinmc42
A very good question I did not know the answer too.
Compute module CM3+ datasheet page 15

Bank0 and 1 GPIOs are available for general use. GPIO0 to GPIO27 are bank0 and GPIO28-45 makeup bank1. GPIO0-27VDD is the power supply for bank0 and GPIO28-45VDD is the power supply forbank1. SDXVDD is the supply for bank2 on CM3+ Lite. These supplies can be in the range 1.8V-3.3V(see Table 7) and are not optional; each bank must be powered, even when none of the GPIOs for thatbank are used.


Important if using lower voltage eMMC or something?

Re: Broadcom & voltage

Posted: Sat Jun 22, 2019 11:33 am
by Gavinmc42
eMMC has it's own voltage.
https://www.raspberrypi.org/documentati ... CM_2p0.pdf

This would be hardwired on normal Pi's? but on Computes you could change the GPIO voltages.
Could be handy for 1.8V i2c etc.

I have never used Computes, thanks for the question.
I now have much better idea of them now and they might actually be useful because of these GPIO voltage options :D