is it necessary to set GPIO pin to high-Z when entering Suspend mode in i.MX51 Androd 10.4?

[vincent_rtk]

When entering suspend mode, in order to reduce current, is it necessary to set GPIO pins? For example, set pin to High-Z (input) mode to reduce power consumption. In other application platform, it is required to do it. However, in i.MX51 bsp, it is not seen.

Does i.MX51 not need the action?

[david_babin · Accepted solution]

To minimize power consumption, you need to ensure that your system does not allow current to flow into or out of GPIOs when in suspend mode. This is system dependent and depends on your hardware. Simply setting all GPIOs to high-Z may float a peripheral chip’s input, causing the peripheral chip to draw more current than necessary.

While in standby, suspend, or other low-power mode, here are some guidelines for i.MX GPIO Outputs that drive peripheral inputs:

1. Check each peripheral input for function. For example, if the input is STBY_B (negative logic standby input), then the GPIO should drive it low.

2. If the input does not affect peripheral chip IDD, then check if the peripheral chip has on-chip pull-up/down or your system has pull-up/down resistors. Program the GPIO such that there is no current drain through resistors.

3. If #1 and #2 above do not apply, then (preferably) the GPIO can be programmed as an output driving low.

While in standby, suspend, or other low-power mode, here are some guidelines for i.MX GPIO Inputs that are driven from peripheral outputs. Check each peripheral output for its state during suspend, standby, or other low-power mode.

A. If the peripheral output is low, then ensure that the GPIO is programmed either as an input without pull-up/down (high-Z) or as an input with pull-down.

B. If the peripheral output is high, then ensure that the GPIO is programmed either as an input without pull-up/down (high-Z) or as an input with pull-up.