Particle ONE402MEA Manual page 8

Because this is an analog switch, the nRF52840 current limitations, 2 mA in standard drive (the
default), and 9 mA in high drive also apply on the M8 side of the analog switch. The switch is rated
up to 300 MHz, higher than the highest UART or I2C baud rate. The 3.3V recommended maximum
for GPIO also applies on the M8 connector.
The CAN bus has a separate hardware transceiver and is not considered to be GPIO and does not
have a 3.3V limitation.