CSI Unused Data Input Pull-Down

[jaredm]

We are developing hardware using the RT1052 and 12-bit CMOS sensor. The RT1052 uses the CSI in 16-bit Bayer mode, the 12-bit sensor is connected to data[11:0], and data[15:12] are unused. When receiving pixel data, we would like data[15:12] to be 0's (to avoid an additional software masking step.) We have two options:

1. Connect BGA pads for data[15:12] to GND.

2. Leave BGA pads for data[15:12] NC, and enable the internal pull-down.

Option 2 is preferred, but it is unclear whether it will work.

On the RT1052 device, does the peripheral logic override the I/O pad options? Or can the I/O pad options be configured independently from the peripheral logic? For instances, can registers IOMUXC_SW_PAD_CTL_PAD_GPIO_AD_B1_04:07 be configured to enable pull-downs, even when the signals are used as peripheral function CSI data[15:12]?

Thanks in advance.

[gusarambula · Accepted solution]

Hello Jaredm,

You may setup the pin pad regardless of the peripheral function as to enable the internal pull-downs.

These internal pull-down resistors would allow for low input read on the floating pins in some scenarios, but since these internal pull downs are weak, the input value may be affected by noise, so it’s not recommended for critical signals. I would recommend tying to ground as to make sure that you won’t have unwanted values on your application under any operating conditions.

I hope that this information helps!

Regards,
Gustavo