SCLA021A September 2019 – April 2021 SN74HC00 , SN74HCS08-Q1
It is extremely common for smart thermostats to utilize wireless interfaces such as Wi-Fi™, ZigBee™, or Bluetooth™ to connect to a local network. In many designs, the simplest method to achieve this is to utilize pre-built and pre-approved modules. These modules often have limited voltage operation ranges, and to support their usage, voltage-level shifters are typically required between the extremely low power processor, often operating as low as 1.2 V, and the wireless module, commonly operating at 3.3 V.
The most common communication protocols used between the processor and wireless interface are SDIO and UART. Each is addressed specifically in the following sections.