This may help: SC16IS752 I2C-SPI to Dual Channel UART Converter Module
CJMCU SC16IS752 I2C-SPI to Dual Channel UART Converter Module Each module will give you two additional serial channels. SPI requires 3 connections common to all modules and an additional CS\ Chip Select connection. This will allow you to match the bauds to the peripherals. These have a 64 byte FIFO (First In First Out) buffer so that will give you time to do things while data is coming in from a sensor.