Why IoT Devices Choose RTOS Over Linux

Let’s first take a look at the TIOBE index in December 2020:

C language has ranked first for several months, surpassing JAVA and Python, indicating that the Internet of Things has reached a very popular level.

Although many embedded systems can be well managed with less complex software, networked devices require more powerful systems.

The software for IoT devices should have:

• Scalability: to adapt to various categories of devices

• Modularity: to select the required components

• Connectivity: to move data in and out of devices via Wi-Fi, Ethernet, USB, or Bluetooth.

• Reliability: preferably with relevant security certification

1. Scalability

A scalable RTOS can help you improve development efficiency, reduce development costs, and shorten time to market.

Historically, embedded systems have been built around 8-bit and 16-bit MCUs, but the price of 32-bit MCUs has been rapidly decreasing, with sales growing quickly, making them the most popular MCUs.

2. Modularity

Many RTOS manufacturers have continuously improved their RTOS ecosystem, with more and more middleware and components, but one characteristic is modularity.

Familiar RTOS like µC/OS, RT-Thread, FreeRTOS, etc., have expanded many components around RTOS.

3. Connectivity

Network connectivity is very important for the Internet of Things, and the key point is “connection,” otherwise it’s just “things” and cannot be called the Internet of Things.

If the RTOS has a corresponding protocol stack, that’s best, as it can save development time. Also, if the chip comes with the required protocol stack, it’s even better, as it can save memory on the device and reduce costs.

4. Reliability

The reliability of this point, I believe, needs no explanation; anyone who has done development can understand how troublesome it is to encounter bugs after a product has been running for a while…

Therefore, not only the visible physical products need certification, but the “invisible” software also needs certification.

Linux has many uses in embedded devices, especially those that provide graphically rich user interfaces.

However, compared to real-time operating systems (RTOS), Linux has a “disadvantage”: memory usage. Even though Linux can be shrunk by removing unnecessary tools and system services for embedded systems, it is still very large (relative to RTOS).

It cannot run on 8-bit or 16-bit MCUs at all, and even many newer 32-bit MCUs do not have enough onboard RAM for the Linux kernel.

ARM Cortex-M series is very suitable for IoT MCUs, with hundreds of MCUs based on the popular Cortex-M architecture, usually with only a few hundred KB of memory, and Linux basically cannot run on these chips.