Uno as I2c port expander

Hello all

I'm trying to build a Jetbot from a Jetson nano (self driving car)
It calls for a PCA9685, which handles the PWM externally via I2c that it passes onto the motor driver, likely a l289N.

I've try to make a PCF8574 work, which is sometimes used as an I2c for 16x2 LCDs.
It seems like I'd need to writing via the software and that wouldn't be much better than driving the L289N directly from the Jetson Nanos GPIO.

I'm thinking, I should just be able to get an UNO via I2c to emulate the original PCA9685 and output PWM according?
The bonus is I already have a L289N shield for my UNO.

Can anyone point me towards some info on how to do this?
My searches can't seem to get past arduino port expander tutorials :slight_smile:

Thanks

Of possible use: Master Slave I2C Connection - Arduino Project Hub

Of course, you'll have to program the slave Arduino to translate the I2C comms. to PWM

After extensive searching, it seems like the Arduino firmata is the solution.