Programming Embedded Systems, 2nd Edition

To Use or Not to Use an RTOS

The answer is...it depends. In many cases, there is no clear-cut answer to this question. Many embedded systems can (and do) operate exactly as they need to by using an infinite loop, as we discussed in Chapter 3. These embedded systems do not need to be complicated by adding additional software, such as an RTOS. There’s no prize for making an embedded system more complicated.

Each project should be evaluated on its own. Start with the notion that you do not need an RTOS. Then take a look at the overall system requirements. Make a list of the different software modules the system will need in order to meet these requirements.

Let’s go back to the example of the print server device. The data-flow diagram in Chapter 2 is a good starting point. Some of the modules needed for the print server are an interrupt subsystem to handle timer and peripheral interrupts, a handler for the parallel port to communicate and send data to the printer, a networking stack for communication with computers via the Ethernet controller, a debug module that uses a serial port for output (this is not required, but it is helpful), and possibly a monitor and control command-line interface.

Now you can ask some questions about these modules in the system to find out the responsibilities of each. It might help to draw this out in your project notebook. How will these modules interact with each other? Are the modules independent and standalone or do they have interdependencies? Will ...