TCA9543A multiplexer works when arduino pwered via USB but stops with DC supply

So I'm using an arduino to control an MPR121 (MPR) capacitive sensor, two DRV2605L (DRV) haptic motor boards, and an H-bridge to control two solenoids. I got a TCA9543A I2C multiplexer (TCA) from digikey so I could switch between the two DRV boards as they have a fixed I2C address. I calculated the pullup resistors for the SDA/SCL lines per the TCA data sheet, which was 440-2950 ohms, I used 1Kohm resistors for the pullups for the I2C pins and used 570 ohm resistors for the interrupt and reset pins. All the pullups are connected to 5V. I placed a 100 nF capacitor between the TCA Vcc and GND as a bypass filter.

When connected only with USB, I was able to switch between the two DRV boards and activate the respective motors, but I could not switch both motors on at the same time. When I added the DC supply source either by itself or with the USB, I could detect the TCA and open a switch to detect a DRV with an I2C scanner script, but when I tried to write to the DRV to activate a motor, the motor would not activate. To reiterate all the I2C lines have a 5V 1Kohm pullup and the DRV and TCA operate up to 5.5V.

Addendum: I am using an arduino Uno R3, I need to use the DC supply to power the solenoids, my code runs as expected if the DC supply is not connected. Should I x-post this to the I2C forum?

TCA datasheet

DRV datasheet

Should I x-post this to the I2C forum?

Never cross post anything here, it will get you a ban.

A 1K pull up is a bit small for a 5V I2C system, use a 4K7 instead.

Post you code and post a schematic.

So I’ve attached a rough schematic from fritzing and I’ve attached my code as it’s around 400 lines.

V4.ino (13.7 KB)

So I solved this issue by exchanging the 1k pullup resistors with 10k resistors. After reading up a bit, the minimum pullup resistance for the arduino I2C is ~1800 ohms with a max of 18k. By switching out the resistors for the I2C lines I was now able to switch on both channels of the TCA simultaneously, and the DC supply had no negative impact.