10Pcs 8 Channel 5V/3.3V Iic Uart Spi Ttl Logic Level Converter Bi-Directional ev

Ax input 3.3V TTL level,Bx will output 5V TTL level. Ax input 5V TTL level,Bx will output 3.3V TTL level. Instructions:( for example 3.3V, 5V system conversion).

eBay