Synchronism vs Asynchronism in Firmware

In embedded firmware, especially in connected or real-time systems, performance isn’t just about raw speed. It’s about responsiveness, modularity, and the ability to evolve with changing hardware or new product requirements.

One of the most common pitfalls we see at Toor Connect is firmware designed with synchronous assumptions baked into the architecture. While synchronous logic can feel simple and clean at first, it can silently limit your system’s responsiveness and make it fragile when any part of the hardware stack changes.

Synchronous logic means your firmware waits for an operation to finish before proceeding. This is very common in early-stage or bare-metal development.

Example:

uint8_t data = sensor_read(); // blocks until complete
process(data);

This can work well for:

• Simple MCU projects
• GPIO toggles or fast ADC reads
• Early prototypes

But it becomes a bottleneck when:

• You're using I2C, SPI, or UART (with multi-millisecond delays)
• You need to read from several components concurrently
• Your system must remain responsive to interrupts, UI events, or BLE packets

How Synchronism Kills Modularity

Imagine this scenario:

You start by reading a temperature sensor using a fast ADC:

float temp = read_temperature(); // returns quickly

Later, the design shifts to a digital temperature sensor over I2C. Suddenly that same function now:

• Waits 10–50ms
• Needs retries
• Uses a hardware bus with timing constraints

If your logic layer is synchronously designed, this small hardware change causes:

• Blocking delays in your application logic
• Loss of responsiveness elsewhere in the system
• Complex refactors to “make it work again”

In other words, a “simple” synchronous decision creates tight coupling between the logic and the communication layer, making reuse, replacement, and scalability difficult.

The Asynchronous Approach

Asynchronous firmware is built around non-blocking execution, often using:

• Callbacks
• Interrupts
• Event queues
• State machines
• RTOS message passing

Example (pseudo-code):

start_i2c_read(); // returns immediately
...
on_i2c_complete(data) {
    process(data); // handled when ready
}

In this model:

• Firmware reacts to hardware events instead of polling
• The system stays responsive
• Modules remain loosely coupled and easier to test, extend, or replace

A Word on RTOS: Power and Pitfalls

Using a modern RTOS (like FreeRTOS, Zephyr, or RT-Thread) gives you powerful tools to manage asynchronous flows:

• You can assign tasks per component
• Use queues, events, semaphores to coordinate
• Let the scheduler handle concurrency

But, it’s easy to fall into a trap.

Many developers simulate synchronous code in an RTOS by blocking inside tasks:

for (;;) {
    read_data();      // blocks
    vTaskDelay(100);  // also blocks
}

This works short-term, but when you scale:

• Tasks can deadlock if they block waiting on each other
• Race conditions emerge when multiple tasks touch shared resources
• Priority inversion issues surface if a low-priority task holds a needed lock

RTOS doesn’t fix design problems, it amplifies them if not used thoughtfully.

To avoid this, use RTOS the asynchronous way:

• Rely on queues and events, not delays
• Keep tasks short-lived and reactive
• Avoid tight task-to-task coupling

The Temptation of Delay (and Why It Costs More Later)

Using delay() or a blocking read might seem like an easy way to “get it working”, and in early development, that’s often okay. But over time, blocking becomes a liability:

• It hides bugs
• Hurts responsiveness
• Makes changes expensive

Delays are developer laziness with interest. They cost little now but a lot later.

At Toor Connect, we see it all the time. Teams lose weeks debugging timing problems or rewriting logic because they didn't invest in asynchronous architecture early. Being intentional from the start makes your firmware:

• Easier to scale
• Easier to test
• Cheaper to evolve

At Toor Connect, This is Built-In

We help companies build firmware that’s not just functional, but modular, scalable, and designed for change. Whether you're using bare-metal, an RTOS, or a general purpose OS, we can help make sure your architecture supports non-blocking, event-driven, low-power operation from day one.