the Colibri IMX7D GPIO ( I config them to be UART) is 3.3V, but the peripheral UART TX and RX pins are 5V, if I connect them together, will I damage the IMX7D?
I tried to connect UART TX/RX from imx7D to peripheral UART 5V TX/RX, it works, but not sure if it will damage the chip if I run the UART for long time. pls help
The absolute maximum ratings of the I/O pins are -0.3 to 3.6V. Using the pins outside of this range can permanently damage the SoC. This is what NXP writes in its datasheet. Therefore, we highly do not recommend using interfaces with 5V signals.
The pins feature protection diodes to the ground and the I/O bank rail. If you attach a voltage that is more than 0.3V higher than the I/O rail (3.3V), the diode will start conducting. If the current of the external 5V I/O source is limited (max 20mA), I would actually not expect damages. However, if the peripheral signals are stronger, The diodes can get damaged or the I/O rail could be lifted up to an unhealthy level.
To sum it up. It might work in short terms, but we absolutely not recommend using the I/Os with 5V logic level. We cannot guarantee that there are no damages over time. Please use a (simple) level shifter instead.
We are using such a configuration with limiting the input current to ~800µA per pin quite often and had no issues at all.
For your configuration something about 3,3k or 5,6k should be fine.
5-3,3+0,3V / 0,0005A = 4000Ohms
Still no guarantee as @peter.tx said.
Thanks for your Input.